1
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Yao X, Ren J, Fang L, Sun K, He W. The role and mechanism of Bacillus megaterium strain A14 in inhibiting the cadmium uptake by peanut plants in acidic red soil. J Appl Microbiol 2024; 135:lxae120. [PMID: 38794879 DOI: 10.1093/jambio/lxae120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 04/03/2024] [Accepted: 05/23/2024] [Indexed: 05/26/2024]
Abstract
AIMS This study explores the potential of cadmium (Cd)-resistant bacteria, specifically Bacillus megaterium A14, to decrease Cd accumulation in peanuts, a crop susceptible to metal uptake from contaminated soils, by understanding the bacterium's impact on plant Cd absorption mechanisms. METHODS AND RESULTS Through pot experiments, we observed that A14 inoculation significantly increased peanut biomass under Cd stress conditions, primarily by immobilizing the metal and reducing its bioavailability. The bacterium effectively changed the distribution of Cd, with a notable 46.53% reduction in the exchangeable fraction, which in turn limited the expression of genes related to Cd transport in peanuts. Additionally, A14 enhanced the plant's antioxidant response, improving its tolerance to stress. Microbial analysis through 16S sequencing demonstrated that A14 inoculation altered the peanut rhizosphere, particularly by increasing populations of Firmicutes and Proteobacteria, which play crucial roles in soil remediation from heavy metals. CONCLUSION The A14 strain effectively counters Cd toxicity in peanuts, promoting growth through soil Cd sequestration, root barrier biofilm formation, antioxidant system enhancement, suppression of Cd transport genes, and facilitation of Cd-remediating microorganisms.
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Affiliation(s)
- Xiangzhi Yao
- College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Jingyu Ren
- College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Lirong Fang
- College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Kai Sun
- College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Wei He
- College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
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2
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Barney BM, Dietz BR. Precision control of ammonium release in Azotobacter vinelandii. Microb Biotechnol 2024; 17:e14523. [PMID: 39023513 PMCID: PMC11256883 DOI: 10.1111/1751-7915.14523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2024] [Accepted: 06/27/2024] [Indexed: 07/20/2024] Open
Abstract
The capture and reduction of atmospheric dinitrogen gas to ammonium can be accomplished through the enzyme nitrogenase in a process known as biological nitrogen fixation (BNF), by a class of microbes known as diazotrophs. The diazotroph Azotobacter vinelandii is a model organism for the study of aerobic nitrogen fixation, and in recent years has been promoted as a potential producer of biofertilizers. Prior reports have demonstrated the potential to partially deregulate BNF in A. vinelandii, resulting in accumulation and extracellular release of ammonium. In many cases, deregulation requires the introduction of transgenic genes or elements to yield the desired phenotype, and the long-term stability of these strains has been reported to be somewhat problematic. In this work, we constructed two strains of A. vinelandii where regulation can be precisely controlled without the addition of any foreign genes or genetic markers. Regulation is maintained through native promoters found in A. vinelandii that can be induced through the addition of extraneous galactose. These strains result in varied degrees of regulation of BNF, and as a result, the release of extracellular ammonium is controlled in a precise, and galactose concentration-dependent manner. In addition, these strains yield high biomass levels, similar to the wild-type A. vinelandii strain and are further able to produce high percentages of the bioplastic polyhydroxybutyrate.
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Affiliation(s)
- Brett M. Barney
- Department of Bioproducts and Biosystems EngineeringUniversity of MinnesotaSt. PaulMinnesotaUSA
- Biotechnology InstituteUniversity of MinnesotaSt. PaulMinnesotaUSA
| | - Benjamin R. Dietz
- Department of Bioproducts and Biosystems EngineeringUniversity of MinnesotaSt. PaulMinnesotaUSA
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3
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Lv F, Zhan Y, Feng H, Sun W, Yin C, Han Y, Shao Y, Xue W, Jiang S, Ma Y, Hu H, Wei J, Yan Y, Lin M. Integrated Hfq-interacting RNAome and transcriptomic analysis reveals complex regulatory networks of nitrogen fixation in root-associated Pseudomonas stutzeri A1501. mSphere 2024; 9:e0076223. [PMID: 38747590 PMCID: PMC11332353 DOI: 10.1128/msphere.00762-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Accepted: 04/10/2024] [Indexed: 06/26/2024] Open
Abstract
The RNA chaperone Hfq acts as a global regulator of numerous biological processes, such as carbon/nitrogen metabolism and environmental adaptation in plant-associated diazotrophs; however, its target RNAs and the mechanisms underlying nitrogen fixation remain largely unknown. Here, we used enhanced UV cross-linking immunoprecipitation coupled with high-throughput sequencing to identify hundreds of Hfq-binding RNAs probably involved in nitrogen fixation, carbon substrate utilization, biofilm formation, and other functions. Collectively, these processes endow strain A1501 with the requisite capabilities to thrive in the highly competitive rhizosphere. Our findings revealed a previously uncharted landscape of Hfq target genes. Notable among these is nifM, encoding an isomerase necessary for nitrogenase reductase solubility; amtB, encoding an ammonium transporter; oprB, encoding a carbohydrate porin; and cheZ, encoding a chemotaxis protein. Furthermore, we identified more than 100 genes of unknown function, which expands the potential direct regulatory targets of Hfq in diazotrophs. Our data showed that Hfq directly interacts with the mRNA of regulatory proteins (RsmA, AlgU, and NifA), regulatory ncRNA RsmY, and other potential targets, thus revealing the mechanistic links in nitrogen fixation and other metabolic pathways. IMPORTANCE Numerous experimental approaches often face challenges in distinguishing between direct and indirect effects of Hfq-mediated regulation. New technologies based on high-throughput sequencing are increasingly providing insight into the global regulation of Hfq in gene expression. Here, enhanced UV cross-linking immunoprecipitation coupled with high-throughput sequencing was employed to identify the Hfq-binding sites and potential targets in the root-associated Pseudomonas stutzeri A1501 and identify hundreds of novel Hfq-binding RNAs that are predicted to be involved in metabolism, environmental adaptation, and nitrogen fixation. In particular, we have shown Hfq interactions with various regulatory proteins' mRNA and their potential targets at the posttranscriptional level. This study not only enhances our understanding of Hfq regulation but, importantly, also provides a framework for addressing integrated regulatory network underlying root-associated nitrogen fixation.
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Affiliation(s)
- Fanyang Lv
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yuhua Zhan
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Haichao Feng
- College of Agriculture, Henan University, Kaifeng, Henan, China
| | - Wenyue Sun
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Changyan Yin
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yueyue Han
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yahui Shao
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Wei Xue
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Shanshan Jiang
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yiyuan Ma
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Haonan Hu
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jinfeng Wei
- College of Agriculture, Henan University, Kaifeng, Henan, China
| | - Yongliang Yan
- Biotechnology Research Institute/National Key Laboratory of Agricultural Microbiology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Min Lin
- College of Agriculture, Henan University, Kaifeng, Henan, China
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4
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Ambrosio R, Burgos Herrera G, Do Nascimento M, Pagnussat LA, Curatti L. Competitive fitness and stability of ammonium-excreting Azotobacter vinelandii strains in the soil. Appl Microbiol Biotechnol 2024; 108:378. [PMID: 38888816 PMCID: PMC11189346 DOI: 10.1007/s00253-024-13231-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 06/03/2024] [Accepted: 06/08/2024] [Indexed: 06/20/2024]
Abstract
Non-symbiotic N2-fixation would greatly increase the versatility of N-biofertilizers for sustainable agriculture. Genetic modification of diazotrophic bacteria has successfully enhanced NH4+ release. In this study, we compared the competitive fitness of A. vinelandii mutant strains, which allowed us to analyze the burden of NH4+ release under a broad dynamic range. Long-term competition assays under regular culture conditions confirmed a large burden for NH4+ release, exclusion by the wt strain, phenotypic instability, and loss of the ability to release NH4+. In contrast, co-inoculation in mild autoclaved soil showed a much longer co-existence with the wt strain and a stable NH4+ release phenotype. All genetically modified strains increased the N content and changed its chemical speciation in the soil. This study contributes one step forward towards bridging a knowledge gap between molecular biology laboratory research and the incorporation of N from the air into the soil in a molecular species suitable for plant nutrition, a crucial requirement for developing improved bacterial inoculants for economic and environmentally sustainable agriculture. KEY POINTS: • Genetic engineering for NH4+ excretion imposes a fitness burden on the culture medium • Large phenotypic instability for NH4+-excreting bacteria in culture medium • Lower fitness burden and phenotypic instability for NH4+-excreting bacteria in soil.
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Affiliation(s)
- Rafael Ambrosio
- Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC), Consejo Nacional de Investigaciones Científicas y Técnicas, Vieytes 3103, 7600, Mar del PlataBuenos Aires, Argentina
- Fundación para Investigaciones Biológicas Aplicadas, Mar del Plata, Buenos Aires, Argentina
- Instituto de Agrobiotecnología del Litoral, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional del Litoral, Santa Fe, Santa Fe, Argentina
| | - Gonzalo Burgos Herrera
- Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC), Consejo Nacional de Investigaciones Científicas y Técnicas, Vieytes 3103, 7600, Mar del PlataBuenos Aires, Argentina
- Fundación para Investigaciones Biológicas Aplicadas, Mar del Plata, Buenos Aires, Argentina
| | - Mauro Do Nascimento
- Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC), Consejo Nacional de Investigaciones Científicas y Técnicas, Vieytes 3103, 7600, Mar del PlataBuenos Aires, Argentina
- Fundación para Investigaciones Biológicas Aplicadas, Mar del Plata, Buenos Aires, Argentina
| | - Luciana Anabella Pagnussat
- Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC), Consejo Nacional de Investigaciones Científicas y Técnicas, Vieytes 3103, 7600, Mar del PlataBuenos Aires, Argentina
- Fundación para Investigaciones Biológicas Aplicadas, Mar del Plata, Buenos Aires, Argentina
- Facultad de Ciencias Agrarias, Universidad Nacional de Mar del Plata, Balcarce, Buenos Aires, Argentina
| | - Leonardo Curatti
- Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC), Consejo Nacional de Investigaciones Científicas y Técnicas, Vieytes 3103, 7600, Mar del PlataBuenos Aires, Argentina.
- Fundación para Investigaciones Biológicas Aplicadas, Mar del Plata, Buenos Aires, Argentina.
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5
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Jones EM, Marken JP, Silver PA. Synthetic microbiology in sustainability applications. Nat Rev Microbiol 2024; 22:345-359. [PMID: 38253793 DOI: 10.1038/s41579-023-01007-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/12/2023] [Indexed: 01/24/2024]
Abstract
Microorganisms are a promising means to address many societal sustainability challenges owing to their ability to thrive in diverse environments and interface with the microscale chemical world via diverse metabolic capacities. Synthetic biology can engineer microorganisms by rewiring their regulatory networks or introducing new functionalities, enhancing their utility for target applications. In this Review, we provide a broad, high-level overview of various research efforts addressing sustainability challenges through synthetic biology, emphasizing foundational microbiological research questions that can accelerate the development of these efforts. We introduce an organizational framework that categorizes these efforts along three domains - factory, farm and field - that are defined by the extent to which the engineered microorganisms interface with the natural external environment. Different application areas within the same domain share many fundamental challenges, highlighting productive opportunities for cross-disciplinary collaborations between researchers working in historically disparate fields.
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Affiliation(s)
- Ethan M Jones
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
| | - John P Marken
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Resnick Sustainability Institute, California Institute of Technology, Pasadena, CA, USA
| | - Pamela A Silver
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA.
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA.
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6
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Chakraborty S, Venkataraman M, Infante V, Pfleger BF, Ané JM. Scripting a new dialogue between diazotrophs and crops. Trends Microbiol 2024; 32:577-589. [PMID: 37770375 PMCID: PMC10950843 DOI: 10.1016/j.tim.2023.08.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 08/14/2023] [Accepted: 08/15/2023] [Indexed: 09/30/2023]
Abstract
Diazotrophs are bacteria and archaea that can reduce atmospheric dinitrogen (N2) into ammonium. Plant-diazotroph interactions have been explored for over a century as a nitrogen (N) source for crops to improve agricultural productivity and sustainability. This scientific quest has generated much information about the molecular mechanisms underlying the function, assembly, and regulation of nitrogenase, ammonium assimilation, and plant-diazotroph interactions. This review presents various approaches to manipulating N fixation activity, ammonium release by diazotrophs, and plant-diazotroph interactions. We discuss the research avenues explored in this area, propose potential future routes, emphasizing engineering at the metabolic level via biorthogonal signaling, and conclude by highlighting the importance of biocontrol measures and public acceptance.
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Affiliation(s)
- Sanhita Chakraborty
- Department of Bacteriology, University of Wisconsin - Madison, Madison, WI, USA
| | - Maya Venkataraman
- Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, WI, USA
| | - Valentina Infante
- Department of Bacteriology, University of Wisconsin - Madison, Madison, WI, USA
| | - Brian F Pfleger
- Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, WI, USA
| | - Jean-Michel Ané
- Department of Bacteriology, University of Wisconsin - Madison, Madison, WI, USA; Department of Agronomy, University of Wisconsin - Madison, Madison, WI, USA.
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7
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Sun Z, Sun C, Zhang T, Liu J, Wang X, Feng J, Li S, Tang S, Jin K. Soil microbial community variation among different land use types in the agro-pastoral ecotone of northern China is likely to be caused by anthropogenic activities. Front Microbiol 2024; 15:1390286. [PMID: 38841072 PMCID: PMC11150776 DOI: 10.3389/fmicb.2024.1390286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 05/10/2024] [Indexed: 06/07/2024] Open
Abstract
There are various types of land use in the agricultural and pastoral areas of northern China, including natural grassland and artificial grassland, scrub land, forest land and farmland, may change the soil microbial community However, the soil microbial communities in these different land use types remain poorly understood. In this study, we compared soil microbial communities in these five land use types within the agro-pastoral ecotone of northern China. Our results showed that land use has had a considerable impact on soil bacterial and fungal community structures. Bacterial diversity was highest in shrubland and lowest in natural grassland; fungal diversity was highest in woodland. Microbial network structural complexity also differed significantly among land use types. The lower complexity of artificial grassland and farmland may be a result of the high intensity of anthropogenic activities in these two land-use types, while the higher structural complexity of the shrubland and woodland networks characterised by low-intensity management may be a result of low anthropogenic disturbance. Correlation analysis of soil properties (e.g., soil physicochemical properties, soil nutrients, and microbiomass carbon and nitrogen levels) and soil microbial communities demonstrated that although microbial taxa were correlated to some extent with soil environmental factors, these factors did not sufficiently explain the microbial community differences among land use types. Understanding variability among soil microbial communities within agro-pastoral areas of northern China is critical for determining the most effective land management strategies and conserving microbial diversity at the regional level.
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Affiliation(s)
- Zhaokai Sun
- Key Laboratory for Model Innovation in Forage Production Efficiency, Ministry of Agriculture and Rural Affairs, Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot, China
| | - Chongzhi Sun
- Key Laboratory for Model Innovation in Forage Production Efficiency, Ministry of Agriculture and Rural Affairs, Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot, China
| | - Tongrui Zhang
- Key Laboratory for Model Innovation in Forage Production Efficiency, Ministry of Agriculture and Rural Affairs, Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot, China
| | - Jia Liu
- School of Grass Academy, Qingdao Agriculture University, Qingdao, China
| | - Xinning Wang
- Key Laboratory for Model Innovation in Forage Production Efficiency, Ministry of Agriculture and Rural Affairs, Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot, China
| | - Jing Feng
- School of Grass Academy, Qingdao Agriculture University, Qingdao, China
| | - Shucheng Li
- Anhui Science and Technology University, College of Agriculture, Huainan, China
| | - Shiming Tang
- Key Laboratory for Model Innovation in Forage Production Efficiency, Ministry of Agriculture and Rural Affairs, Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot, China
| | - Ke Jin
- Key Laboratory for Model Innovation in Forage Production Efficiency, Ministry of Agriculture and Rural Affairs, Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot, China
- Department of International Cooperation, Chinese Academy of Agricultural Sciences, Beijing, China
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8
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Yoshidome D, Hidaka M, Miyanaga T, Ito Y, Kosono S, Nishiyama M. Glutamate production from aerial nitrogen using the nitrogen-fixing bacterium Klebsiella oxytoca. Commun Biol 2024; 7:443. [PMID: 38605181 PMCID: PMC11009414 DOI: 10.1038/s42003-024-06147-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 04/05/2024] [Indexed: 04/13/2024] Open
Abstract
Glutamate is an essential biological compound produced for various therapeutic and nutritional applications. The current glutamate production process requires a large amount of ammonium, which is generated through the energy-consuming and CO2-emitting Haber-Bosch process; therefore, the development of bio-economical glutamate production processes is required. We herein developed a strategy for glutamate production from aerial nitrogen using the nitrogen-fixing bacterium Klebsiella oxytoca. We showed that a simultaneous supply of glucose and citrate as carbon sources enhanced the nitrogenase activity of K. oxytoca. In the presence of glucose and citrate, K. oxytoca strain that was genetically engineered to increase the supply of 2-oxoglutarate, a precursor of glutamate synthesis, produced glutamate extracellularly more than 1 g L-1 from aerial nitrogen. This strategy offers a sustainable and eco-friendly manufacturing process to produce various nitrogen-containing compounds using aerial nitrogen.
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Affiliation(s)
- Daisuke Yoshidome
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
| | - Makoto Hidaka
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Toka Miyanaga
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Yusuke Ito
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- Kikkoman Corporation, Noda, Chiba, Japan
| | - Saori Kosono
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- RIKEN Center for Sustainable Resource Science, Wako, Saitama, Japan
| | - Makoto Nishiyama
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
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9
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Dietz BR, Olszewski NE, Barney BM. Enhanced extracellular ammonium release in the plant endophyte Gluconacetobacter diazotrophicus through genome editing. Microbiol Spectr 2024; 12:e0247823. [PMID: 38038458 PMCID: PMC10783055 DOI: 10.1128/spectrum.02478-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 10/27/2023] [Indexed: 12/02/2023] Open
Abstract
IMPORTANCE Our results demonstrate increased extracellular ammonium release in the endophyte plant growth-promoting bacterium Gluconacetobacter diazotrophicus. Strains were constructed in a manner that leaves no antibiotic markers behind, such that these strains contain no transgenes. Levels of ammonium achieved by cultures of modified G. diazotrophicus strains reached concentrations of approximately 18 mM ammonium, while wild-type G. diazotrophicus remained much lower (below 50 µM). These findings demonstrate a strong potential for further improving the biofertilizer potential of this important microbe.
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Affiliation(s)
- Benjamin R. Dietz
- Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota, USA
| | - Neil E. Olszewski
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Brett M. Barney
- Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota, USA
- Biotechnology Institute, University of Minnesota, St. Paul, Minnesota, USA
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10
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García-Tomsig NI, García-Rodriguez FM, Guedes-García SK, Millán V, Becker A, Robledo M, Jiménez-Zurdo JI. A double-negative feedback loop between NtrBC and a small RNA rewires nitrogen metabolism in legume symbionts. mBio 2023; 14:e0200323. [PMID: 37850753 PMCID: PMC10746234 DOI: 10.1128/mbio.02003-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 09/05/2023] [Indexed: 10/19/2023] Open
Abstract
IMPORTANCE Root nodule endosymbioses between diazotrophic rhizobia and legumes provide the largest input of combined N to the biosphere, thus representing an alternative to harmful chemical fertilizers for sustainable crop production. Rhizobia have evolved intricate strategies to coordinate N assimilation for their own benefit with N2 fixation to sustain plant growth. The rhizobial N status is transduced by the NtrBC two-component system, the seemingly ubiquitous form of N signal transduction in Proteobacteria. Here, we show that the regulatory sRNA NfeR1 (nodule formation efficiency RNA) of the alfalfa symbiont Sinorhizobium meliloti is transcribed from a complex promoter repressed by NtrC in a N-dependent manner and feedback silences ntrBC by complementary base-pairing. These findings unveil a more prominent role of NtrC as a transcriptional repressor than hitherto anticipated and a novel RNA-based mechanism for NtrBC regulation. The NtrBC-NfeR1 double-negative feedback loop accurately rewires symbiotic S. meliloti N metabolism and is likely conserved in α-rhizobia.
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Affiliation(s)
- Natalia I. García-Tomsig
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Fernando M. García-Rodriguez
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Sabina K. Guedes-García
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Vicenta Millán
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Anke Becker
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Marburg, Germany
| | - Marta Robledo
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - José I. Jiménez-Zurdo
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
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11
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Wiskich A, Rapson T. Economics of Emerging Ammonia Fertilizer Production Methods - a Role for On-Farm Synthesis? CHEMSUSCHEM 2023; 16:e202300565. [PMID: 37495900 DOI: 10.1002/cssc.202300565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 07/19/2023] [Accepted: 07/24/2023] [Indexed: 07/28/2023]
Abstract
Prospects of recent promising methods of producing ammonia without fossil fuels are discussed. Despite demonstrating efficiency gains over previous similar approaches, the novel biological and electrochemical pathways require further large improvements to compete with electricity-powered Haber-Bosch. As some literature asserts that future production will shift to smaller scales, such as on-farm, we qualitatively discuss the economics of scale of future green ammonia production.
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Affiliation(s)
- Anthony Wiskich
- Commonwealth Science and Industry Research Organisation, Australia
| | - Trevor Rapson
- Commonwealth Science and Industry Research Organisation, Australia
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12
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Tang Y, Qin D, Tian Z, Chen W, Ma Y, Wang J, Yang J, Yan D, Dixon R, Wang YP. Diurnal switches in diazotrophic lifestyle increase nitrogen contribution to cereals. Nat Commun 2023; 14:7516. [PMID: 37980355 PMCID: PMC10657418 DOI: 10.1038/s41467-023-43370-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 11/07/2023] [Indexed: 11/20/2023] Open
Abstract
Uncoupling of biological nitrogen fixation from ammonia assimilation is a prerequisite step for engineering ammonia excretion and improvement of plant-associative nitrogen fixation. In this study, we have identified an amino acid substitution in glutamine synthetase, which provides temperature sensitive biosynthesis of glutamine, the intracellular metabolic signal of the nitrogen status. As a consequence, negative feedback regulation of genes and enzymes subject to nitrogen regulation, including nitrogenase is thermally controlled, enabling ammonia excretion in engineered Escherichia coli and the plant-associated diazotroph Klebsiella oxytoca at 23 °C, but not at 30 °C. We demonstrate that this temperature profile can be exploited to provide diurnal oscillation of ammonia excretion when variant bacteria are used to inoculate cereal crops. We provide evidence that diurnal temperature variation improves nitrogen donation to the plant because the inoculant bacteria have the ability to recover and proliferate at higher temperatures during the daytime.
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Affiliation(s)
- Yuqian Tang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences & School of Advanced Agricultural Sciences, Peking University, Beijing, 100871, China
| | - Debin Qin
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences & School of Advanced Agricultural Sciences, Peking University, Beijing, 100871, China
| | - Zhexian Tian
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences & School of Advanced Agricultural Sciences, Peking University, Beijing, 100871, China
| | - Wenxi Chen
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences & School of Advanced Agricultural Sciences, Peking University, Beijing, 100871, China
| | - Yuanxi Ma
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences & School of Advanced Agricultural Sciences, Peking University, Beijing, 100871, China
| | - Jilong Wang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences & School of Advanced Agricultural Sciences, Peking University, Beijing, 100871, China
| | - Jianguo Yang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences & School of Advanced Agricultural Sciences, Peking University, Beijing, 100871, China
| | - Dalai Yan
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Ray Dixon
- Department of Molecular Microbiology, John Innes Centre, Norwich, NR4 7UH, UK.
| | - Yi-Ping Wang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences & School of Advanced Agricultural Sciences, Peking University, Beijing, 100871, China.
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13
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Turk-Kubo KA, Gradoville MR, Cheung S, Cornejo-Castillo FM, Harding KJ, Morando M, Mills M, Zehr JP. Non-cyanobacterial diazotrophs: global diversity, distribution, ecophysiology, and activity in marine waters. FEMS Microbiol Rev 2023; 47:fuac046. [PMID: 36416813 PMCID: PMC10719068 DOI: 10.1093/femsre/fuac046] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 09/15/2022] [Accepted: 11/17/2022] [Indexed: 12/17/2023] Open
Abstract
Biological dinitrogen (N2) fixation supplies nitrogen to the oceans, supporting primary productivity, and is carried out by some bacteria and archaea referred to as diazotrophs. Cyanobacteria are conventionally considered to be the major contributors to marine N2 fixation, but non-cyanobacterial diazotrophs (NCDs) have been shown to be distributed throughout ocean ecosystems. However, the biogeochemical significance of marine NCDs has not been demonstrated. This review synthesizes multiple datasets, drawing from cultivation-independent molecular techniques and data from extensive oceanic expeditions, to provide a comprehensive view into the diversity, biogeography, ecophysiology, and activity of marine NCDs. A NCD nifH gene catalog was compiled containing sequences from both PCR-based and PCR-free methods, identifying taxa for future studies. NCD abundances from a novel database of NCD nifH-based abundances were colocalized with environmental data, unveiling distinct distributions and environmental drivers of individual taxa. Mechanisms that NCDs may use to fuel and regulate N2 fixation in response to oxygen and fixed nitrogen availability are discussed, based on a metabolic analysis of recently available Tara Oceans expedition data. The integration of multiple datasets provides a new perspective that enhances understanding of the biology, ecology, and biogeography of marine NCDs and provides tools and directions for future research.
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Affiliation(s)
- Kendra A Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
| | - Mary R Gradoville
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
- Columbia River Inter-Tribal Fish Commission, Portland, OR, United States
| | - Shunyan Cheung
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
| | - Francisco M Cornejo-Castillo
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
- Department of Marine Biology and Oceanography, Institute of Marine Sciences (ICM-CSIC), Pg. Marítim Barceloneta, 37-49 08003 Barcelona, Spain
| | - Katie J Harding
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
- Marine Biology Research Division, Scripps Institute of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093, United States
| | - Michael Morando
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
| | - Matthew Mills
- Department of Earth System Science, Stanford University, 473 Via Ortega, Stanford, CA 94305, United States
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
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14
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Van Gelder K, Oliveira-Filho ER, Messina CD, Venado RE, Wilker J, Rajasekar S, Ané JM, Amthor JS, Hanson AD. Running the numbers on plant synthetic biology solutions to global problems. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2023; 335:111815. [PMID: 37543223 DOI: 10.1016/j.plantsci.2023.111815] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 07/30/2023] [Accepted: 08/02/2023] [Indexed: 08/07/2023]
Abstract
Synthetic biology and metabolic engineering promise to deliver sustainable solutions to global problems such as phasing out fossil fuels and replacing industrial nitrogen fixation. While this promise is real, scale matters, and so do knock-on effects of implementing solutions. Both scale and knock-on effects can be estimated by 'Fermi calculations' (aka 'back-of-envelope calculations') that use uncontroversial input data plus simple arithmetic to reach rough but reliable conclusions. Here, we illustrate how this is done and how informative it can be using two cases: oilcane (sugarcane engineered to accumulate triglycerides instead of sugar) as a source of bio-jet fuel, and nitrogen fixation by bacteria in mucilage secreted by maize aerial roots. We estimate that oilcane could meet no more than about 1% of today's U.S. jet fuel demand if grown on all current U.S. sugarcane land and that, if cane land were expanded to meet two-thirds of this demand, the fertilizer and refinery requirements would create a large carbon footprint. Conversely, we estimate that nitrogen fixation in aerial-root mucilage could replace up to 10% of the fertilizer nitrogen applied to U.S. maize, that 2% of plant carbon income used for growth would suffice to fuel the fixation, and that this extra carbon consumption would likely reduce grain yield only slightly.
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Affiliation(s)
- Kristen Van Gelder
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA
| | | | - Carlos D Messina
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA
| | - Rafael E Venado
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jennifer Wilker
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Shanmugam Rajasekar
- Department of Agronomy, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jean-Michel Ané
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Agronomy, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jeffrey S Amthor
- Center for Ecosystem Science and Society, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Andrew D Hanson
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA.
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15
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Zhao X, Song Y, Wang T, Hua C, Hu R, Shang Y, Shi H, Chen S. Glutamine synthetase and GlnR regulate nitrogen metabolism in Paenibacillus polymyxa WLY78. Appl Environ Microbiol 2023; 89:e0013923. [PMID: 37668407 PMCID: PMC10537745 DOI: 10.1128/aem.00139-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 07/12/2023] [Indexed: 09/06/2023] Open
Abstract
Paenibacillus polymyxa WLY78, a N2-fixing bacterium, has great potential use as a biofertilizer in agriculture. Recently, we have revealed that GlnR positively and negatively regulates the transcription of the nif (nitrogen fixation) operon (nifBHDKENXhesAnifV) in P. polymyxa WLY78 by binding to two loci of the nif promoter according to nitrogen availability. However, the regulatory mechanisms of nitrogen metabolism mediated by GlnR in the Paenibacillus genus remain unclear. In this study, we have revealed that glutamine synthetase (GS) and GlnR in P. polymyxa WLY78 play a key role in the regulation of nitrogen metabolism. P. polymyxa GS (encoded by glnA within glnRA) and GS1 (encoded by glnA1) belong to distinct groups: GSI-α and GSI-β. Both GS and GS1 have the enzyme activity to convert NH4+ and glutamate into glutamine, but only GS is involved in the repression by GlnR. GlnR represses transcription of glnRA under excess nitrogen, while it activates the expression of glnA1 under nitrogen limitation. GlnR simultaneously activates and represses the expression of amtBglnK and gcvH in response to nitrogen availability. Also, GlnR regulates the expression of nasA, nasD1D2, nasT, glnQHMP, and glnS. IMPORTANCE In this study, we have revealed that Paenibacillus polymyxa GlnR uses multiple mechanisms to regulate nitrogen metabolism. GlnR activates or represses or simultaneously activates and inhibits the transcription of nitrogen metabolism genes in response to nitrogen availability. The multiple regulation mechanisms employed by P. polymyxa GlnR are very different from Bacillus subtilis GlnR which represses nitrogen metabolism under excess nitrogen. Both GS encoded by glnA within the glnRA operon and GS1 encoded by glnA1 in P. polymyxa WLY78 are involved in ammonium assimilation, but only GS is required for regulating GlnR activity. The work not only provides significant insight into understanding the interplay of GlnR and GS in nitrogen metabolism but also provides guidance for improving nitrogen fixation efficiency by modulating nitrogen metabolism.
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Affiliation(s)
- Xiyun Zhao
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Yi Song
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Tianshu Wang
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Chongchong Hua
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Rui Hu
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Yimin Shang
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Haowen Shi
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
| | - Sanfeng Chen
- Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University, Beijing, China
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16
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Sanow S, Kuang W, Schaaf G, Huesgen P, Schurr U, Roessner U, Watt M, Arsova B. Molecular Mechanisms of Pseudomonas-Assisted Plant Nitrogen Uptake: Opportunities for Modern Agriculture. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2023; 36:536-548. [PMID: 36989040 DOI: 10.1094/mpmi-10-22-0223-cr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Pseudomonas spp. make up 1.6% of the bacteria in the soil and are found throughout the world. More than 140 species of this genus have been identified, some beneficial to the plant. Several species in the family Pseudomonadaceae, including Azotobacter vinelandii AvOP, Pseudomonas stutzeri A1501, Pseudomonas stutzeri DSM4166, Pseudomonas szotifigens 6HT33bT, and Pseudomonas sp. strain K1 can fix nitrogen from the air. The genes required for these reactions are organized in a nitrogen fixation island, obtained via horizontal gene transfer from Klebsiella pneumoniae, Pseudomonas stutzeri, and Azotobacter vinelandii. Today, this island is conserved in Pseudomonas spp. from different geographical locations, which, in turn, have evolved to deal with different geo-climatic conditions. Here, we summarize the molecular mechanisms behind Pseudomonas-driven plant growth promotion, with particular focus on improving plant performance at limiting nitrogen (N) and improving plant N content. We describe Pseudomonas-plant interaction strategies in the soil, noting that the mechanisms of denitrification, ammonification, and secondary metabolite signaling are only marginally explored. Plant growth promotion is dependent on the abiotic conditions and differs at sufficient and deficient N. The molecular controls behind different plant responses are not fully elucidated. We suggest that superposition of transcriptome, proteome, and metabolome data and their integration with plant phenotype development through time will help fill these gaps. The aim of this review is to summarize the knowledge behind Pseudomonas-driven nitrogen fixation and to point to possible agricultural solutions. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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Affiliation(s)
- Stefan Sanow
- Institute for Bio- and Geosciences, Plant Sciences (IBG-2), Forschungszentrum Juelich GmbH, Germany
- School of BioSciences, Faculty of Science, The University of Melbourne, Parkville, 3010 Victoria, Australia
| | - Weiqi Kuang
- College of life and Environmental Sciences, Hunan University of Arts and Science, China
| | - Gabriel Schaaf
- Institute of Crop Science and Resource Conservation, University of Bonn, 53115 Bonn, Germany
| | - Pitter Huesgen
- Central institute for Engineering, Electronics and Analytics (ZEA-3), Forschungszentrum Juelich GmbH, Germany
| | - Ulrich Schurr
- Institute for Bio- and Geosciences, Plant Sciences (IBG-2), Forschungszentrum Juelich GmbH, Germany
| | - Ute Roessner
- Research School of Biology, The Australian National University, Acton, 2601 Australian Capital Territory, Australia
| | - Michelle Watt
- School of BioSciences, Faculty of Science, The University of Melbourne, Parkville, 3010 Victoria, Australia
| | - Borjana Arsova
- Institute for Bio- and Geosciences, Plant Sciences (IBG-2), Forschungszentrum Juelich GmbH, Germany
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17
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Boyer NR, Tokmina-Lukaszewska M, Bueno Batista M, Mus F, Dixon R, Bothner B, Peters JW. Structural insights into redox signal transduction mechanisms in the control of nitrogen fixation by the NifLA system. Proc Natl Acad Sci U S A 2023; 120:e2302732120. [PMID: 37459513 PMCID: PMC10372690 DOI: 10.1073/pnas.2302732120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 06/15/2023] [Indexed: 07/20/2023] Open
Abstract
NifL is a conformationally dynamic flavoprotein responsible for regulating the activity of the σ54-dependent activator NifA to control the transcription of nitrogen fixation (nif) genes in response to intracellular oxygen, cellular energy, or nitrogen availability. The NifL-NifA two-component system is the master regulatory system for nitrogen fixation. NifL serves as a sensory protein, undergoing signal-dependent conformational changes that modulate its interaction with NifA, forming the NifL-NifA complex, which inhibits NifA activity in conditions unsuitable for nitrogen fixation. While NifL-NifA regulation is well understood, these conformationally flexible proteins have eluded previous attempts at structure determination. In work described here, we advance a structural model of the NifL dimer supported by a combination of scattering techniques and mass spectrometry (MS)-coupled structural analyses that report on the average structure in solution. Using a combination of small angle X-ray scattering-derived electron density maps and MS-coupled surface labeling, we investigate the conformational dynamics responsible for NifL oxygen and energy responses. Our results reveal conformational differences in the structure of NifL under reduced and oxidized conditions that provide the basis for a model for modulating NifLA complex formation in the regulation of nitrogen fixation in response to oxygen in the model diazotroph, Azotobacter vinelandii.
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Affiliation(s)
- Nathaniel R. Boyer
- Institute of Biological Chemistry, Washington State University, Pullman, WA99164
| | | | - Marcelo Bueno Batista
- Department of Molecular Microbiology, John Innes Centre, NorwichNR4 7UH, United Kingdom
| | - Florence Mus
- Institute of Biological Chemistry, Washington State University, Pullman, WA99164
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK73019
| | - Ray Dixon
- Department of Molecular Microbiology, John Innes Centre, NorwichNR4 7UH, United Kingdom
| | - Brian Bothner
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT59717
| | - John W. Peters
- Institute of Biological Chemistry, Washington State University, Pullman, WA99164
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK73019
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18
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Bathe U, Leong BJ, Van Gelder K, Barbier GG, Henry CS, Amthor JS, Hanson AD. Respiratory energy demands and scope for demand expansion and destruction. PLANT PHYSIOLOGY 2023; 191:2093-2103. [PMID: 36271857 PMCID: PMC10069906 DOI: 10.1093/plphys/kiac493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 10/09/2022] [Indexed: 06/16/2023]
Abstract
Nonphotosynthetic plant metabolic processes are powered by respiratory energy, a limited resource that metabolic engineers—like plants themselves—must manage prudently.
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Affiliation(s)
| | | | | | | | - Christopher S Henry
- Mathematics and Computer Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Jeffrey S Amthor
- Northern Arizona University Center for Ecosystem Science and Society, Flagstaff, Arizona 86011, USA
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19
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Guo K, Yang J, Yu N, Luo L, Wang E. Biological nitrogen fixation in cereal crops: Progress, strategies, and perspectives. PLANT COMMUNICATIONS 2023; 4:100499. [PMID: 36447432 PMCID: PMC10030364 DOI: 10.1016/j.xplc.2022.100499] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/07/2022] [Accepted: 11/28/2022] [Indexed: 05/04/2023]
Abstract
Nitrogen is abundant in the atmosphere but is generally the most limiting nutrient for plants. The inability of many crop plants, such as cereals, to directly utilize freely available atmospheric nitrogen gas means that their growth and production often rely heavily on the application of chemical fertilizers, which leads to greenhouse gas emissions and the eutrophication of water. By contrast, legumes gain access to nitrogen through symbiotic association with rhizobia. These bacteria convert nitrogen gas into biologically available ammonia in nodules through a process termed symbiotic biological nitrogen fixation, which plays a decisive role in ecosystem functioning. Engineering cereal crops that can fix nitrogen like legumes or associate with nitrogen-fixing microbiomes could help to avoid the problems caused by the overuse of synthetic nitrogen fertilizer. With the development of synthetic biology, various efforts have been undertaken with the aim of creating so-called "N-self-fertilizing" crops capable of performing autonomous nitrogen fixation to avoid the need for chemical fertilizers. In this review, we briefly summarize the history and current status of engineering N-self-fertilizing crops. We also propose several potential biotechnological approaches for incorporating biological nitrogen fixation capacity into non-legume plants.
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Affiliation(s)
- Kaiyan Guo
- Shanghai Key Laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, Shanghai 200234, China; National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Jun Yang
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Nan Yu
- Shanghai Key Laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, Shanghai 200234, China.
| | - Li Luo
- School of Life Sciences, Shanghai Key Laboratory of Bioenergy Crops, Shanghai University, Shanghai 200444, China.
| | - Ertao Wang
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.
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20
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Martin Del Campo JS, Rigsbee J, Bueno Batista M, Mus F, Rubio LM, Einsle O, Peters JW, Dixon R, Dean DR, Dos Santos PC. Overview of physiological, biochemical, and regulatory aspects of nitrogen fixation in Azotobacter vinelandii. Crit Rev Biochem Mol Biol 2023; 57:492-538. [PMID: 36877487 DOI: 10.1080/10409238.2023.2181309] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
Abstract
Understanding how Nature accomplishes the reduction of inert nitrogen gas to form metabolically tractable ammonia at ambient temperature and pressure has challenged scientists for more than a century. Such an understanding is a key aspect toward accomplishing the transfer of the genetic determinants of biological nitrogen fixation to crop plants as well as for the development of improved synthetic catalysts based on the biological mechanism. Over the past 30 years, the free-living nitrogen-fixing bacterium Azotobacter vinelandii emerged as a preferred model organism for mechanistic, structural, genetic, and physiological studies aimed at understanding biological nitrogen fixation. This review provides a contemporary overview of these studies and places them within the context of their historical development.
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Affiliation(s)
| | - Jack Rigsbee
- Department of Chemistry, Wake Forest University, Winston-Salem, NC, USA
| | | | - Florence Mus
- Institute of Biological Chemistry, Washington State University, Pullman, WA, USA
| | - Luis M Rubio
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA/CSIC), Pozuelo de Alarcón, Spain
| | - Oliver Einsle
- Department of Biochemistry, University of Freiburg, Freiburg, Germany
| | - John W Peters
- Institute of Biological Chemistry, Washington State University, Pullman, WA, USA
| | - Ray Dixon
- Department of Molecular Microbiology, John Innes Centre, Norwich, UK
| | - Dennis R Dean
- Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA
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21
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Bennett EM, Murray JW, Isalan M. Engineering Nitrogenases for Synthetic Nitrogen Fixation: From Pathway Engineering to Directed Evolution. BIODESIGN RESEARCH 2023; 5:0005. [PMID: 37849466 PMCID: PMC10521693 DOI: 10.34133/bdr.0005] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 12/24/2022] [Indexed: 10/19/2023] Open
Abstract
Globally, agriculture depends on industrial nitrogen fertilizer to improve crop growth. Fertilizer production consumes fossil fuels and contributes to environmental nitrogen pollution. A potential solution would be to harness nitrogenases-enzymes capable of converting atmospheric nitrogen N2 to NH3 in ambient conditions. It is therefore a major goal of synthetic biology to engineer functional nitrogenases into crop plants, or bacteria that form symbiotic relationships with crops, to support growth and reduce dependence on industrially produced fertilizer. This review paper highlights recent work toward understanding the functional requirements for nitrogenase expression and manipulating nitrogenase gene expression in heterologous hosts to improve activity and oxygen tolerance and potentially to engineer synthetic symbiotic relationships with plants.
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Affiliation(s)
- Emily M. Bennett
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - James W. Murray
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Mark Isalan
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
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22
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Haskett TL, Geddes BA, Paramasivan P, Green P, Chitnavis S, Mendes MD, Jorrín B, Knights HE, Bastholm TR, Ramsay JP, Oldroyd GED, Poole PS. Rhizopine biosensors for plant-dependent control of bacterial gene expression. Environ Microbiol 2023; 25:383-396. [PMID: 36428208 PMCID: PMC10107442 DOI: 10.1111/1462-2920.16288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 11/23/2022] [Indexed: 11/27/2022]
Abstract
Engineering signalling between plants and microbes could be exploited to establish host-specificity between plant-growth-promoting bacteria and target crops in the environment. We previously engineered rhizopine-signalling circuitry facilitating exclusive signalling between rhizopine-producing (RhiP) plants and model bacterial strains. Here, we conduct an in-depth analysis of rhizopine-inducible expression in bacteria. We characterize two rhizopine-inducible promoters and explore the bacterial host-range of rhizopine biosensor plasmids. By tuning the expression of rhizopine uptake genes, we also construct a new biosensor plasmid pSIR05 that has minimal impact on host cell growth in vitro and exhibits markedly improved stability of expression in situ on RhiP barley roots compared to the previously described biosensor plasmid pSIR02. We demonstrate that a sub-population of Azorhizobium caulinodans cells carrying pSIR05 can sense rhizopine and activate gene expression when colonizing RhiP barley roots. However, these bacteria were mildly defective for colonization of RhiP barley roots compared to the wild-type parent strain. This work provides advancement towards establishing more robust plant-dependent control of bacterial gene expression and highlights the key challenges remaining to achieve this goal.
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Affiliation(s)
| | - Barney A Geddes
- Department of Plant Sciences, University of Oxford, Oxford, UK
- Department of Microbiological Sciences, North Dakota State University, Fargo, North Dakota, USA
| | | | - Patrick Green
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Samir Chitnavis
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Marta D Mendes
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Beatriz Jorrín
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | | | - Tahlia R Bastholm
- Curtin Medical School and Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia
| | - Joshua P Ramsay
- Curtin Medical School and Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia
| | - Giles E D Oldroyd
- Sainsbury Laboratory, University of Cambridge, Cambridge, UK
- Crop Science Centre, University of Cambridge, Cambridge, UK
| | - Philip S Poole
- Department of Plant Sciences, University of Oxford, Oxford, UK
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23
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Molecular Mechanism and Agricultural Application of the NifA-NifL System for Nitrogen Fixation. Int J Mol Sci 2023; 24:ijms24020907. [PMID: 36674420 PMCID: PMC9866876 DOI: 10.3390/ijms24020907] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 12/27/2022] [Accepted: 12/30/2022] [Indexed: 01/06/2023] Open
Abstract
Nitrogen-fixing bacteria execute biological nitrogen fixation through nitrogenase, converting inert dinitrogen (N2) in the atmosphere into bioavailable nitrogen. Elaborating the molecular mechanisms of orderly and efficient biological nitrogen fixation and applying them to agricultural production can alleviate the "nitrogen problem". Azotobacter vinelandii is a well-established model bacterium for studying nitrogen fixation, utilizing nitrogenase encoded by the nif gene cluster to fix nitrogen. In Azotobacter vinelandii, the NifA-NifL system fine-tunes the nif gene cluster transcription by sensing the redox signals and energy status, then modulating nitrogen fixation. In this manuscript, we investigate the transcriptional regulation mechanism of the nif gene in autogenous nitrogen-fixing bacteria. We discuss how autogenous nitrogen fixation can better be integrated into agriculture, providing preliminary comprehensive data for the study of autogenous nitrogen-fixing regulation.
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24
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Grenier V, Gonzalez E, Brereton NJB, Pitre FE. Dynamics of bacterial and archaeal communities during horse bedding and green waste composting. PeerJ 2023; 11:e15239. [PMID: 37159830 PMCID: PMC10163874 DOI: 10.7717/peerj.15239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 03/28/2023] [Indexed: 05/11/2023] Open
Abstract
Organic waste decomposition can make up substantial amounts of municipal greenhouse emissions during decomposition. Composting has the potential to reduce these emissions as well as generate sustainable fertilizer. However, our understanding of how complex microbial communities change to drive the chemical and biological processes of composting is still limited. To investigate the microbiota associated with organic waste decomposition, initial composting feedstock (Litter), three composting windrows of 1.5 months (Young phase), 3 months (Middle phase) and 12 months (Aged phase) old, and 24-month-old mature Compost were sampled to assess physicochemical properties, plant cell wall composition and the microbial community using 16S rRNA gene amplification. A total of 2,612 Exact Sequence Variants (ESVs) included 517 annotated as putative species and 694 as genera which together captured 57.7% of the 3,133,873 sequences, with the most abundant species being Thermobifida fusca, Thermomonospora chromogena and Thermobifida bifida. Compost properties changed rapidly over time alongside the diversity of the compost community, which increased as composting progressed, and multivariate analysis indicated significant variation in community composition between each time-point. The abundance of bacteria in the feedstock is strongly correlated with the presence of organic matter and the abundance of plant cell wall components. Temperature and pH are the most strongly correlated parameters with bacterial abundance in the thermophilic and cooling phases/mature compost respectively. Differential abundance analysis revealed 810 ESVs annotated as species significantly varied in relative abundance between Litter and Young phase, 653 between the Young and Middle phases, 1182 between Middle and Aged phases and 663 between Aged phase and mature Compost. These changes indicated that structural carbohydrates and lignin degrading species were abundant at the beginning of the thermophilic phase, especially members of the Firmicute and Actinobacteria phyla. A high diversity of species capable of putative ammonification and denitrification were consistently found throughout the composting phases, whereas a limited number of nitrifying bacteria were identified and were significantly enriched within the later mesophilic composting phases. High microbial community resolution also revealed unexpected species which could be beneficial for agricultural soils enriched with mature compost or for the deployment of environmental and plant biotechnologies. Understanding the dynamics of these microbial communities could lead to improved waste management strategies and the development of input-specific composting protocols to optimize carbon and nitrogen transformation and promote a diverse and functional microflora in mature compost.
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Affiliation(s)
- Vanessa Grenier
- Department of Biological Sciences, Université de Montréal, Montréal, Québec, Canada
- Institut de Recherche en Biologie Végétale, Montréal, Québec, Canada
| | - Emmanuel Gonzalez
- Department of Human Genetics, McGill University, Montréal, Québec, Canada
- Canadian Centre for Computational Genomics, McGill Genome Centre, McGill University, Montréal, Québec, Canada
- Gerald Bronfman Department of Oncology, McGill University, Montréal, Québec, Canada
| | - Nicholas JB Brereton
- School of Biology and Environmental Science, University College Dublin, Dublin, Ireland
| | - Frederic E. Pitre
- Department of Biological Sciences, Université de Montréal, Montréal, Québec, Canada
- Institut de Recherche en Biologie Végétale, Montréal, Québec, Canada
- Montreal Botanical Garden, Montréal, Québec, Canada
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Minamisawa K. Mitigation of greenhouse gas emission by nitrogen-fixing bacteria. Biosci Biotechnol Biochem 2022; 87:7-12. [PMID: 36354103 DOI: 10.1093/bbb/zbac177] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Accepted: 11/01/2022] [Indexed: 11/11/2022]
Abstract
Chemical nitrogen fixation by the Haber-Bosch method permitted industrial-scale fertilizer production that supported global population growth, but simultaneously released reactive nitrogen into the environment. This minireview highlights the potential for bacterial nitrogen fixation and mitigation of greenhouse gas (GHG) emissions from soybean and rice fields. Nitrous oxide (N2O), a GHG, is mainly emitted from agricultural use of nitrogen fertilizer and symbiotic nitrogen fixation. Some rhizobia have a denitrifying enzyme system that includes an N2O reductase and are able to mitigate N2O emission from the rhizosphere of leguminous plants. Type II methane (CH4)-oxidizing bacteria (methanotrophs) are endophytes in paddy rice roots and fix N2 using CH4 (a GHG) as an energy source, mitigating the emission of CH4 and reducing nitrogen fertilizer usage. Thus, symbiotic nitrogen fixation shows potential for GHG mitigation in soybean and rice fields while simultaneously supporting sustainable agriculture.
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Affiliation(s)
- Kiwamu Minamisawa
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi, Japan
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26
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Gluconacetobacter diazotrophicus Gene Fitness during Diazotrophic Growth. Appl Environ Microbiol 2022; 88:e0124122. [PMID: 36374093 PMCID: PMC9746312 DOI: 10.1128/aem.01241-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Plant growth-promoting (PGP) bacteria are important to the development of sustainable agricultural systems. PGP microbes that fix atmospheric nitrogen (diazotrophs) could minimize the application of industrially derived fertilizers and function as a biofertilizer. The bacterium Gluconacetobacter diazotrophicus is a nitrogen-fixing PGP microbe originally discovered in association with sugarcane plants, where it functions as an endophyte. It also forms endophyte associations with a range of other agriculturally relevant crop plants. G. diazotrophicus requires microaerobic conditions for diazotrophic growth. We generated a transposon library for G. diazotrophicus and cultured the library under various growth conditions and culture medium compositions to measure fitness defects associated with individual transposon inserts (transposon insertion sequencing [Tn-seq]). Using this library, we probed more than 3,200 genes and ascertained the importance of various genes for diazotrophic growth of this microaerobic endophyte. We also identified a set of essential genes. IMPORTANCE Our results demonstrate a succinct set of genes involved in diazotrophic growth for G. diazotrophicus, with a lower degree of redundancy than what is found in other model diazotrophs. The results will serve as a valuable resource for those interested in biological nitrogen fixation and will establish a baseline data set for plant free growth, which could complement future studies related to the endophyte relationship.
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Li Q, Zhang H, Song Y, Wang M, Hua C, Li Y, Chen S, Dixon R, Li J. Alanine synthesized by alanine dehydrogenase enables ammonium-tolerant nitrogen fixation in Paenibacillus sabinae T27. Proc Natl Acad Sci U S A 2022; 119:e2215855119. [PMID: 36459643 PMCID: PMC9894248 DOI: 10.1073/pnas.2215855119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 11/08/2022] [Indexed: 12/04/2022] Open
Abstract
Most diazotrophs fix nitrogen only under nitrogen-limiting conditions, for example, in the presence of relatively low concentrations of NH4+ (0 to 2 mM). However, Paenibacillus sabinae T27 exhibits an unusual pattern of nitrogen regulation of nitrogen fixation, since although nitrogenase activities are high under nitrogen-limiting conditions (0 to 3 mM NH4+) and are repressed under conditions of nitrogen sufficiency (4 to 30 mM NH4+), nitrogenase activity is reestablished when very high levels of NH4+ (30 to 300 mM) are present in the medium. To further understand this pattern of nitrogen fixation regulation, we carried out transcriptome analyses of P. sabinae T27 in response to increasing ammonium concentrations. As anticipated, the nif genes were highly expressed, either in the absence of fixed nitrogen or in the presence of a high concentration of NH4+ (100 mM), but were subject to negative feedback regulation at an intermediate concentration of NH4+ (10 mM). Among the differentially expressed genes, ald1, encoding alanine dehydrogenase (ADH1), was highly expressed in the presence of a high level of NH4+ (100 mM). Mutation and complementation experiments revealed that ald1 is required for nitrogen fixation at high ammonium concentrations. We demonstrate that alanine, synthesized by ADH1 from pyruvate and NH4+, inhibits GS activity, leading to a low intracellular glutamine concentration that prevents feedback inhibition of GS and mimics nitrogen limitation, enabling activation of nif transcription by the nitrogen-responsive regulator GlnR in the presence of high levels of extracellular ammonium.
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Affiliation(s)
- Qin Li
- State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing100193, People’s Republic of China
| | - Haowei Zhang
- State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing100193, People’s Republic of China
| | - Yi Song
- State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing100193, People’s Republic of China
| | - Minyang Wang
- State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing100193, People’s Republic of China
| | - Chongchong Hua
- State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing100193, People’s Republic of China
| | - Yashi Li
- State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing100193, People’s Republic of China
| | - Sanfeng Chen
- State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing100193, People’s Republic of China
| | - Ray Dixon
- Department of Molecular Microbiology, John Innes Centre, NorwichNR4 7UH, United Kingdom
| | - Jilun Li
- State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing100193, People’s Republic of China
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Song W, Wang J, Hou L. Effects of frequency and amount of stover mulching on soil nitrogen and the microbial functional guilds of the endosphere and rhizosphere. Front Microbiol 2022; 13:976154. [PMID: 36090112 PMCID: PMC9449521 DOI: 10.3389/fmicb.2022.976154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 08/05/2022] [Indexed: 11/20/2022] Open
Abstract
Stover mulching as a conservation and sustainable agricultural practice is beneficial for maintaining soil nitrogen (N) requirements and plant health. The microbial functional guilds of the root and rhizosphere are important factors in the soil nitrogen cycle. However, it is unclear how the frequency and amount of stover mulching influence microbial functional guilds in the root and rhizosphere. Therefore, we investigated the responses of the microbial functional guilds in the endosphere and rhizosphere to maize stover mulching amounts (0, 1/3, 2/3, and total stover mulching every year) and frequencies (once every 3 years and twice every 3 years) under 10-year no-till management. The bacterial functional guilds of nitrogen fixation, nitrification, and anaerobic nitrate oxidation displayed the significantly correlation with C/N, total nitrogen, NO3−, and NH4+. The fungal functional guilds of plant pathogens and saprotrophs showed significantly correlations with C/N, total nitrogen, and NO3−. Moreover, we found that bacterial guilds play a pivotal role in maintaining N requirements at the jointing stage, whereas root endophytic fungal guilds play a more important role than bacterial guilds in regulating plant health at the mature stage. The frequency and amount of stover mulching had significant effects on the microbial functional guilds in the root and rhizosphere. Our data suggest that stover mulch application twice every 3 years is the optimal mulching frequency because it yielded the lowest abundance of nitrifying and anaerobic nitrate-oxidising bacteria and the highest abundance of nitrogen-fixing bacteria at the jointing stage, as well as the lowest abundance of fungal plant pathogens in roots at the mature stage.
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Affiliation(s)
- Wenchen Song
- Key Laboratory of Ecology and Environment in Minority Areas, Minzu University of China, National Ethnic Affairs Commission, Beijing, China
- College of Life and Environmental Sciences, Minzu University of China, Beijing, China
- *Correspondence: Wenchen Song,
| | - Jing Wang
- College of Life and Environmental Sciences, Minzu University of China, Beijing, China
| | - Lei Hou
- Beijing Pollution Source Related Affair Management Center, Beijing, China
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Control of nitrogen fixation and ammonia excretion in Azorhizobium caulinodans. PLoS Genet 2022; 18:e1010276. [PMID: 35727841 PMCID: PMC9249168 DOI: 10.1371/journal.pgen.1010276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 07/01/2022] [Accepted: 05/26/2022] [Indexed: 11/19/2022] Open
Abstract
Due to the costly energy demands of nitrogen (N) fixation, diazotrophic bacteria have evolved complex regulatory networks that permit expression of the catalyst nitrogenase only under conditions of N starvation, whereas the same condition stimulates upregulation of high-affinity ammonia (NH3) assimilation by glutamine synthetase (GS), preventing excess release of excess NH3 for plants. Diazotrophic bacteria can be engineered to excrete NH3 by interference with GS, however control is required to minimise growth penalties and prevent unintended provision of NH3 to non-target plants. Here, we tested two strategies to control GS regulation and NH3 excretion in our model cereal symbiont Azorhizobium caulinodans AcLP, a derivative of ORS571. We first attempted to recapitulate previous work where mutation of both PII homologues glnB and glnK stimulated GS shutdown but found that one of these genes was essential for growth. Secondly, we expressed unidirectional adenylyl transferases (uATs) in a ΔglnE mutant of AcLP which permitted strong GS shutdown and excretion of NH3 derived from N2 fixation and completely alleviated negative feedback regulation on nitrogenase expression. We placed a uAT allele under control of the NifA-dependent promoter PnifH, permitting GS shutdown and NH3 excretion specifically under microaerobic conditions, the same cue that initiates N2 fixation, then deleted nifA and transferred a rhizopine nifAL94Q/D95Q-rpoN controller plasmid into this strain, permitting coupled rhizopine-dependent activation of N2 fixation and NH3 excretion. This highly sophisticated and multi-layered control circuitry brings us a step closer to the development of a "synthetic symbioses” where N2 fixation and NH3 excretion could be specifically activated in diazotrophic bacteria colonising transgenic rhizopine producing cereals, targeting delivery of fixed N to the crop while preventing interaction with non-target plants. Inoculation of cereal crops with associative diazotrophic bacteria that convert atmospheric nitrogen (N2) into ammonia (NH3) could be used to sustainably improve delivery of nitrogen to crops. However, due to the costly energy demands of N2 fixation, bacteria restrict excess production of NH3 and release to the plants. Diazotrophs can be engineered for excess NH3 production and release, however genetic control is required to minimise growth penalties and prevent unintended provision of NH3 to non-target weed species. Here, we engineer coupled control of N2 fixation and NH3 release in response to the signalling molecule rhizopine supplemented in vitro. This control circuitry represents a prototype for the future development of a “synthetic symbiosis” where bacterial N2 fixation and NH3 excretion could be specifically activated following colonisation of transgenic rhizopine producing cereals in the field, minimising bacterial energy requirements and preventing provision of NH3 to non-target plants.
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A highly conserved core bacterial microbiota with nitrogen-fixation capacity inhabits the xylem sap in maize plants. Nat Commun 2022; 13:3361. [PMID: 35688828 PMCID: PMC9187771 DOI: 10.1038/s41467-022-31113-w] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 06/06/2022] [Indexed: 12/13/2022] Open
Abstract
Microbiomes are important for crop performance. However, a deeper knowledge of crop-associated microbial communities is needed to harness beneficial host-microbe interactions. Here, by assessing the assembly and functions of maize microbiomes across soil types, climate zones, and genotypes, we found that the stem xylem selectively recruits highly conserved microbes dominated by Gammaproteobacteria. We showed that the proportion of bacterial taxa carrying the nitrogenase gene (nifH) was larger in stem xylem than in other organs such as root and leaf endosphere. Of the 25 core bacterial taxa identified in xylem sap, several isolated strains were confirmed to be active nitrogen-fixers or to assist with biological nitrogen fixation. On this basis, we established synthetic communities (SynComs) consisting of two core diazotrophs and two helpers. GFP-tagged strains and 15N isotopic dilution method demonstrated that these SynComs do thrive and contribute, through biological nitrogen fixation, 11.8% of the total N accumulated in maize stems. These core taxa in xylem sap represent an untapped resource that can be exploited to increase crop productivity. The plant xylem microbiota remains understudied. Here, the authors characterise the xylem microbiota in maize plants finding that some bacteria carried N fixing genes. By using synthetic communities the authors confirm that xylem inhabiting and N fixing bacteria provide the host plant with N.
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31
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Han Y, Li C, Yan Y, Lin M, Ke X, Zhang Y, Zhan Y. Post-transcriptional control of bacterial nitrogen metabolism by regulatory noncoding RNAs. World J Microbiol Biotechnol 2022; 38:126. [PMID: 35666348 PMCID: PMC9170634 DOI: 10.1007/s11274-022-03287-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 04/12/2022] [Indexed: 12/04/2022]
Abstract
Nitrogen metabolism is the most basic process of material and energy metabolism in living organisms, and processes involving the uptake and use of different nitrogen sources are usually tightly regulated at the transcriptional and post-transcriptional levels. Bacterial regulatory noncoding RNAs are novel post-transcriptional regulators that repress or activate the expression of target genes through complementarily pairing with target mRNAs; therefore, these noncoding RNAs play an important regulatory role in many physiological processes, such as bacterial substance metabolism and stress response. In recent years, a study found that noncoding RNAs play a vital role in the post-transcriptional regulation of nitrogen metabolism, which is currently a hot topic in the study of bacterial nitrogen metabolism regulation. In this review, we present an overview of recent advances that increase our understanding on the regulatory roles of bacterial noncoding RNAs and describe in detail how noncoding RNAs regulate biological nitrogen fixation and nitrogen metabolic engineering. Furthermore, our goal is to lay a theoretical foundation for better understanding the molecular mechanisms in bacteria that are involved in environmental adaptations and metabolically-engineered genetic modifications.
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Affiliation(s)
- Yueyue Han
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Chao Li
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yongliang Yan
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Min Lin
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Xiubin Ke
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yunhua Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China. .,School of Resources and Environment, Anhui Agricultural University, Hefei, China.
| | - Yuhua Zhan
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China.
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Abstract
Inoculation of cereals with diazotrophic (N2-fixing) bacteria offers a sustainable alternative to the application of nitrogen fertilizers in agriculture. While natural diazotrophs have evolved multilayered regulatory mechanisms that couple N2 fixation with assimilation of the product NH3 and prevent release to plants, genetic modifications can permit excess production and excretion of NH3. However, a lack of stringent host-specificity for root colonization by the bacteria would allow growth promotion of target and nontarget plants species alike. Here, we exploit synthetic transkingdom signaling to establish plant host-specific control of the N2-fixation catalyst nitrogenase in Azorhizobium caulinodans occupying barley roots. This work demonstrates how partner-specific interactions can be established to avoid potential growth promotion of nontarget plants. Engineering N2-fixing symbioses between cereals and diazotrophic bacteria represents a promising strategy to sustainably deliver biologically fixed nitrogen (N) in agriculture. We previously developed novel transkingdom signaling between plants and bacteria, through plant production of the bacterial signal rhizopine, allowing control of bacterial gene expression in association with the plant. Here, we have developed both a homozygous rhizopine producing (RhiP) barley line and a hybrid rhizopine uptake system that conveys upon our model bacterium Azorhizobium caulinodans ORS571 (Ac) 103-fold improved sensitivity for rhizopine perception. Using this improved genetic circuitry, we established tight rhizopine-dependent transcriptional control of the nitrogenase master regulator nifA and the N metabolism σ-factor rpoN, which drove nitrogenase expression and activity in vitro and in situ by bacteria colonizing RhiP barley roots. Although in situ nitrogenase activity was suboptimally effective relative to the wild-type strain, activation was specific to RhiP barley and was not observed on the roots of wild-type plants. This work represents a key milestone toward the development of a synthetic plant-controlled symbiosis in which the bacteria fix N2 only when in contact with the desired host plant and are prevented from interaction with nontarget plant species.
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Teo HM, A. A, A. WA, Bhubalan K, S. SNM, C. I. MS, Ng LC. Setting a Plausible Route for Saline Soil-Based Crop Cultivations by Application of Beneficial Halophyte-Associated Bacteria: A Review. Microorganisms 2022; 10:microorganisms10030657. [PMID: 35336232 PMCID: PMC8953261 DOI: 10.3390/microorganisms10030657] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 02/10/2022] [Accepted: 02/14/2022] [Indexed: 02/04/2023] Open
Abstract
The global scale of land salinization has always been a considerable concern for human livelihoods, mainly regarding the food-producing agricultural industries. The latest update suggested that the perpetual salinity problem claimed up to 900 million hectares of agricultural land worldwide, inducing salinity stress among salt-sensitive crops and ultimately reducing productivity and yield. Moreover, with the constant growth of the human population, sustainable solutions are vital to ensure food security and social welfare. Despite that, the current method of crop augmentations via selective breeding and genetic engineering only resulted in mild success. Therefore, using the biological approach of halotolerant plant growth-promoting bacteria (HT-PGPB) as bio-inoculants provides a promising crop enhancement strategy. HT-PGPB has been proven capable of forming a symbiotic relationship with the host plant by instilling induced salinity tolerance (IST) and multiple plant growth-promoting traits (PGP). Nevertheless, the mechanisms and prospects of HT-PGPB application of glycophytic rice crops remains incomprehensively reported. Thus, this review describes a plausible strategy of halophyte-associated HT-PGPB as the future catalyst for rice crop production in salt-dominated land and aims to meet the global Sustainable Development Goals (SDGs) of zero hunger.
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Affiliation(s)
- Han Meng Teo
- Laboratory of Pest, Disease and Microbial Biotechnology (LAPDiM), Faculty of Fisheries and Food Science (FFFS), Universiti Malaysia Terengganu, Kuala Nerus 21030, Terengganu, Malaysia; (H.M.T.); (S.N.M.S.); (M.S.C.I.)
| | - Aziz A.
- Biological Security and Sustainability Research Group, Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, Kuala Nerus 21030, Terengganu, Malaysia;
| | - Wahizatul A. A.
- Institute of Marine Biotechnology, Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, Kuala Nerus 21030, Terengganu, Malaysia; (W.A.A.); (K.B.)
| | - Kesaven Bhubalan
- Institute of Marine Biotechnology, Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, Kuala Nerus 21030, Terengganu, Malaysia; (W.A.A.); (K.B.)
| | - Siti Nordahliawate M. S.
- Laboratory of Pest, Disease and Microbial Biotechnology (LAPDiM), Faculty of Fisheries and Food Science (FFFS), Universiti Malaysia Terengganu, Kuala Nerus 21030, Terengganu, Malaysia; (H.M.T.); (S.N.M.S.); (M.S.C.I.)
| | - Muhamad Syazlie C. I.
- Laboratory of Pest, Disease and Microbial Biotechnology (LAPDiM), Faculty of Fisheries and Food Science (FFFS), Universiti Malaysia Terengganu, Kuala Nerus 21030, Terengganu, Malaysia; (H.M.T.); (S.N.M.S.); (M.S.C.I.)
| | - Lee Chuen Ng
- Laboratory of Pest, Disease and Microbial Biotechnology (LAPDiM), Faculty of Fisheries and Food Science (FFFS), Universiti Malaysia Terengganu, Kuala Nerus 21030, Terengganu, Malaysia; (H.M.T.); (S.N.M.S.); (M.S.C.I.)
- Correspondence:
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Takimoto R, Tatemichi Y, Aoki W, Kosaka Y, Minakuchi H, Ueda M, Kuroda K. A critical role of an oxygen-responsive gene for aerobic nitrogenase activity in Azotobacter vinelandii and its application to Escherichia coli. Sci Rep 2022; 12:4182. [PMID: 35264690 PMCID: PMC8907163 DOI: 10.1038/s41598-022-08007-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 02/28/2022] [Indexed: 12/02/2022] Open
Abstract
Since nitrogenase is irreversibly inactivated within a few minutes after exposure to oxygen, current studies on the heterologous expression of nitrogenase are limited to anaerobic conditions. This study comprehensively identified genes showing oxygen-concentration-dependent expression only under nitrogen-fixing conditions in Azotobacter vinelandii, an aerobic diazotroph. Among the identified genes, nafU, with an unknown function, was greatly upregulated under aerobic nitrogen-fixing conditions. Through replacement and overexpressing experiments, we suggested that nafU is involved in the maintenance of nitrogenase activity under aerobic nitrogenase activity. Furthermore, heterologous expression of nafU in nitrogenase-producing Escherichia coli increased nitrogenase activity under aerobic conditions by 9.7 times. Further analysis of NafU protein strongly suggested its localization in the inner membrane and raised the possibility that this protein may lower the oxygen concentration inside the cells. These findings provide new insights into the mechanisms for maintaining stable nitrogenase activity under aerobic conditions in A. vinelandii and provide a platform to advance the use of nitrogenase under aerobic conditions.
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Affiliation(s)
- Ren Takimoto
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Yuki Tatemichi
- Research and Development Division, Kikkoman Corporation, 338 Noda, Noda, Chiba, 278-0037, Japan
| | - Wataru Aoki
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Yuishin Kosaka
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | | | - Mitsuyoshi Ueda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Kouichi Kuroda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan.
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Coban O, De Deyn GB, van der Ploeg M. Soil microbiota as game-changers in restoration of degraded lands. Science 2022; 375:abe0725. [PMID: 35239372 DOI: 10.1126/science.abe0725] [Citation(s) in RCA: 121] [Impact Index Per Article: 60.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Land degradation reduces soil functioning and, consequently, the services that soil provides. Soil hydrological functions are critical to combat soil degradation and promote soil restoration. Soil microorganisms affect soil hydrology, but the role of soil microbiota in forming and sustaining soil is not well explored. Case studies indicate the potential of soil microorganisms as game-changers in restoring soil functions. We review the state of the art of microorganism use in land restoration technology, the groups of microorganisms with the greatest potential for soil restoration, knowledge of the effect of microorganisms on soil physical properties, and proposed strategies for the long-term restoration of degraded lands. We also emphasize the need to advance the emerging research field of biophysical landscape interactions to support soil-plant ecosystem restoration practices.
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Affiliation(s)
- Oksana Coban
- Department of Environmental Sciences, Wageningen University & Research, Wageningen, Netherlands
| | - Gerlinde B De Deyn
- Department of Environmental Sciences, Wageningen University & Research, Wageningen, Netherlands
| | - Martine van der Ploeg
- Department of Environmental Sciences, Wageningen University & Research, Wageningen, Netherlands
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36
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Markalanda SH, McFadden CJ, Cassidy ST, Wood CW. The soil microbiome increases plant survival and modifies interactions with root endosymbionts in the field. Ecol Evol 2022; 12:e8283. [PMID: 35126998 PMCID: PMC8796929 DOI: 10.1002/ece3.8283] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 09/20/2021] [Accepted: 09/30/2021] [Indexed: 11/07/2022] Open
Abstract
Evidence is accumulating that the soil microbiome-the community of microorganisms living in soils-has a major effect on plant traits and fitness. However, most work to date has taken place under controlled laboratory conditions and has not experimentally disentangled the effect of the soil microbiome on plant performance from the effects of key endosymbiotic constituents. As a result, it is difficult to extrapolate from existing data to understand the role of the soil microbiome in natural plant populations. To address this gap, we performed a field experiment using the black medick Medicago lupulina to test how the soil microbiome influences plant performance and colonization by two root endosymbionts (the mutualistic nitrogen-fixing bacteria Ensifer spp. and the parasitic root-knot nematode Meloidogyne hapla) under natural conditions. We inoculated all plants with nitrogen-fixing bacteria and factorially manipulated the soil microbiome and nematode infection. We found that plants grown in microbe-depleted soil exhibit greater mortality, but that among the survivors, there was no effect of the soil microbiome on plant performance (shoot biomass, root biomass, or shoot-to-root ratio). The soil microbiome also impacted parasitic nematode infection and affected colonization by mutualistic nitrogen-fixing bacteria in a plant genotype-dependent manner, increasing colonization in some plant genotypes and decreasing it in others. Our results demonstrate the soil microbiome has complex effects on plant-endosymbiont interactions and may be critical for survival under natural conditions.
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Affiliation(s)
| | - Connor J. McFadden
- Department of Biological SciencesUniversity of PittsburghPittsburghPennsylvaniaUSA
| | - Steven T. Cassidy
- Department of Biological SciencesUniversity of PittsburghPittsburghPennsylvaniaUSA
- Present address:
Department of BiologyUniversity of FloridaGainesvilleFloridaUSA
| | - Corlett W. Wood
- Department of Biological SciencesUniversity of PittsburghPittsburghPennsylvaniaUSA
- Present address:
Department of BiologyUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
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Maeda I. Potential of Phototrophic Purple Nonsulfur Bacteria to Fix Nitrogen in Rice Fields. Microorganisms 2021; 10:microorganisms10010028. [PMID: 35056477 PMCID: PMC8777916 DOI: 10.3390/microorganisms10010028] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 12/21/2021] [Accepted: 12/22/2021] [Indexed: 11/17/2022] Open
Abstract
Biological nitrogen fixation catalyzed by Mo-nitrogenase of symbiotic diazotrophs has attracted interest because its potential to supply plant-available nitrogen offers an alternative way of using chemical fertilizers for sustainable agriculture. Phototrophic purple nonsulfur bacteria (PNSB) diazotrophically grow under light anaerobic conditions and can be isolated from photic and microaerobic zones of rice fields. Therefore, PNSB as asymbiotic diazotrophs contribute to nitrogen fixation in rice fields. An attempt to measure nitrogen in the oxidized surface layer of paddy soil estimates that approximately 6–8 kg N/ha/year might be accumulated by phototrophic microorganisms. Species of PNSB possess one of or both alternative nitrogenases, V-nitrogenase and Fe-nitrogenase, which are found in asymbiotic diazotrophs, in addition to Mo-nitrogenase. The regulatory networks control nitrogenase activity in response to ammonium, molecular oxygen, and light irradiation. Laboratory and field studies have revealed effectiveness of PNSB inoculation to rice cultures on increases of nitrogen gain, plant growth, and/or grain yield. In this review, properties of the nitrogenase isozymes and regulation of nitrogenase activities in PNSB are described, and research challenges and potential of PNSB inoculation to rice cultures are discussed from a viewpoint of their applications as nitrogen biofertilizer.
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Affiliation(s)
- Isamu Maeda
- Department of Applied Biological Chemistry, School of Agriculture, Utsunomiya University, 350 Minemachi, Utsunomiya 321-8505, Japan
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38
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Wen A, Havens KL, Bloch SE, Shah N, Higgins DA, Davis-Richardson AG, Sharon J, Rezaei F, Mohiti-Asli M, Johnson A, Abud G, Ane JM, Maeda J, Infante V, Gottlieb SS, Lorigan JG, Williams L, Horton A, McKellar M, Soriano D, Caron Z, Elzinga H, Graham A, Clark R, Mak SM, Stupin L, Robinson A, Hubbard N, Broglie R, Tamsir A, Temme K. Enabling Biological Nitrogen Fixation for Cereal Crops in Fertilized Fields. ACS Synth Biol 2021; 10:3264-3277. [PMID: 34851109 DOI: 10.1021/acssynbio.1c00049] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Agricultural productivity relies on synthetic nitrogen fertilizers, yet half of that reactive nitrogen is lost to the environment. There is an urgent need for alternative nitrogen solutions to reduce the water pollution, ozone depletion, atmospheric particulate formation, and global greenhouse gas emissions associated with synthetic nitrogen fertilizer use. One such solution is biological nitrogen fixation (BNF), a component of the complex natural nitrogen cycle. BNF application to commercial agriculture is currently limited by fertilizer use and plant type. This paper describes the identification, development, and deployment of the first microbial product optimized using synthetic biology tools to enable BNF for corn (Zea mays) in fertilized fields, demonstrating the successful, safe commercialization of root-associated diazotrophs and realizing the potential of BNF to replace and reduce synthetic nitrogen fertilizer use in production agriculture. Derived from a wild nitrogen-fixing microbe isolated from agricultural soils, Klebsiella variicola 137-1036 ("Kv137-1036") retains the capacity of the parent strain to colonize corn roots while increasing nitrogen fixation activity 122-fold in nitrogen-rich environments. This technical milestone was then commercialized in less than half of the time of a traditional biological product, with robust biosafety evaluations and product formulations contributing to consumer confidence and ease of use. Tested in multi-year, multi-site field trial experiments throughout the U.S. Corn Belt, fields grown with Kv137-1036 exhibited both higher yields (0.35 ± 0.092 t/ha ± SE or 5.2 ± 1.4 bushels/acre ± SE) and reduced within-field yield variance by 25% in 2018 and 8% in 2019 compared to fields fertilized with synthetic nitrogen fertilizers alone. These results demonstrate the capacity of a broad-acre BNF product to fix nitrogen for corn in field conditions with reliable agronomic benefits.
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Affiliation(s)
- Amy Wen
- Pivot Bio, Berkeley, California 94710, United States
| | | | - Sarah E. Bloch
- Morrison & Foerster LLP, San Francisco, California 94105, United States
| | - Neal Shah
- Pivot Bio, Berkeley, California 94710, United States
| | | | | | - Judee Sharon
- University of Minnesota─Twin Cities, Minneapolis, Minnesota 55401, United States
| | | | | | | | - Gabriel Abud
- Tempo Automation, San Francisco, California 94103, United States
| | - Jean-Michel Ane
- University of Minnesota─Twin Cities, Minneapolis, Minnesota 55401, United States
| | - Junko Maeda
- University of Wisconsin−Madison, Madison, Wisconsin 53706, United States
| | - Valentina Infante
- University of Wisconsin−Madison, Madison, Wisconsin 53706, United States
| | | | | | | | - Alana Horton
- Pivot Bio, Berkeley, California 94710, United States
| | | | | | - Zoe Caron
- Pivot Bio, Berkeley, California 94710, United States
| | | | - Ashley Graham
- Olema Oncology, San Francisco, California 94107, United States
| | | | - San-Ming Mak
- Pivot Bio, Berkeley, California 94710, United States
| | - Laura Stupin
- Pivot Bio, Berkeley, California 94710, United States
| | | | | | | | - Alvin Tamsir
- Pivot Bio, Berkeley, California 94710, United States
| | - Karsten Temme
- Pivot Bio, Berkeley, California 94710, United States
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Nisar A, Gongye X, Huang Y, Khan S, Chen M, Wu B, He M. Genome-Wide Analyses of Proteome and Acetylome in Zymomonas mobilis Under N 2-Fixing Condition. Front Microbiol 2021; 12:740555. [PMID: 34803957 PMCID: PMC8600466 DOI: 10.3389/fmicb.2021.740555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 09/15/2021] [Indexed: 11/30/2022] Open
Abstract
Zymomonas mobilis, a promising candidate for industrial biofuel production, is capable of nitrogen fixation naturally without hindering ethanol production. However, little is known about the regulation of nitrogen fixation in Z. mobilis. We herein conducted a high throughput analysis of proteome and protein acetylation in Z. mobilis under N2-fixing conditions and established its first acetylome. The upregulated proteins mainly belong to processes of nitrogen fixation, motility, chemotaxis, flagellar assembly, energy production, transportation, and oxidation–reduction. Whereas, downregulated proteins are mainly related to energy-consuming and biosynthetic processes. Our acetylome analyses revealed 197 uniquely acetylated proteins, belonging to major pathways such as nitrogen fixation, central carbon metabolism, ammonia assimilation pathway, protein biosynthesis, and amino acid metabolism. Further, we observed acetylation in glycolytic enzymes of central carbon metabolism, the nitrogenase complex, the master regulator NifA, and the enzyme in GS/GOGAT cycle. These findings suggest that protein acetylation may play an important role in regulating various aspects of N2-metabolism in Z. mobilis. This study provides new knowledge of specific proteins and their associated cellular processes and pathways that may be regulated by protein acetylation in Z. mobilis.
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Affiliation(s)
- Ayesha Nisar
- Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu, China.,Graduate School of Chinese Academy of Agricultural Science, Beijing, China
| | - Xiangxu Gongye
- Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu, China
| | - Yuhuan Huang
- Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu, China.,Graduate School of Chinese Academy of Agricultural Science, Beijing, China
| | - Sawar Khan
- Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu, China
| | - Mao Chen
- Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu, China.,Graduate School of Chinese Academy of Agricultural Science, Beijing, China
| | - Bo Wu
- Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu, China
| | - Mingxiong He
- Key Laboratory of Development and Application of Rural Renewable Energy (Ministry of Agriculture and Rural Affairs), Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu, China
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40
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Schnabel T, Sattely E. Improved Stability of Engineered Ammonia Production in the Plant-Symbiont Azospirillum brasilense. ACS Synth Biol 2021; 10:2982-2996. [PMID: 34591447 PMCID: PMC8604774 DOI: 10.1021/acssynbio.1c00287] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bioavailable nitrogen is the limiting nutrient for most agricultural food production. Associative diazotrophs can colonize crop roots and fix their own bioavailable nitrogen from the atmosphere. Wild-type (WT) associative diazotrophs, however, do not release fixed nitrogen in culture and are not known to directly transfer fixed nitrogen resources to plants. Efforts to engineer diazotrophs for plant nitrogen provision as an alternative to chemical fertilization have yielded several strains that transiently release ammonia. However, these strains suffer from selection pressure for nonproducers, which rapidly deplete ammonia accumulating in culture, likely limiting their potential for plant growth promotion (PGP). Here we report engineered Azospirillum brasilense strains with significantly extend ammonia production lifetimes of up to 32 days in culture. Our approach relies on multicopy genetic redundancy of a unidirectional adenylyltransferase (uAT) as a posttranslational mechanism to induce ammonia release via glutamine synthetase deactivation. Testing our multicopy stable strains with the model monocot Setaria viridis in hydroponic monoassociation reveals improvement in plant growth promotion compared to single copy strains. In contrast, inoculation of Zea mays in nitrogen-poor, nonsterile soil does not lead to increased PGP relative to WT, suggesting strain health, resource competition, or colonization capacity in soil may also be limiting factors. In this context, we show that while engineered strains fix more nitrogen per cell compared to WT strains, the expression strength of multiple uAT copies needs to be carefully balanced to maximize ammonia production rates and avoid excessive fitness defects caused by excessive glutamine synthetase shutdown.
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Affiliation(s)
- Tim Schnabel
- Department of Bioengineering, Stanford University, Stanford, California 94305, United States
| | - Elizabeth Sattely
- Department of Chemical Engineering, Stanford University and HHMI, Stanford, California 94305, United States
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41
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Abstract
Azotobacter vinelandii is a nitrogen-fixing free-living soil microbe that has been studied for decades in relation to biological nitrogen fixation (BNF). It is highly amenable to genetic manipulation, helping to unravel the intricate importance of different proteins involved in the process of BNF, including the biosynthesis of cofactors that are essential to assembling the complex metal cofactors that catalyze the difficult reaction of nitrogen fixation. Additionally, A. vinelandii accomplishes this feat while growing as an obligate aerobe, differentiating it from many of the nitrogen-fixing bacteria that are associated with plant roots. The ability to function in the presence of oxygen makes A. vinelandii suitable for application in various potential biotechnological schemes. In this study, we employed transposon sequencing (Tn-seq) to measure the fitness defects associated with disruptions of various genes under nitrogen-fixing dependent growth, versus growth with extraneously provided urea as a nitrogen source. The results allowed us to probe the importance of more than 3,800 genes, revealing that many genes previously believed to be important, can be successfully disrupted without impacting cellular fitness. IMPORTANCE These results provide insights into the functional redundancy in A. vinelandii, while also providing a direct measure of fitness for specific genes associated with the process of BNF. These results will serve as a valuable reference tool in future studies to uncover the mechanisms that govern this process.
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42
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Campbell MA, Coolen MJL, Visscher PT, Morris T, Grice K. Structure and function of Shark Bay microbial communities following tropical cyclone Olwyn: A metatranscriptomic and organic geochemical perspective. GEOBIOLOGY 2021; 19:642-664. [PMID: 34180124 DOI: 10.1111/gbi.12461] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 06/05/2021] [Indexed: 06/13/2023]
Abstract
Shark Bay, Western Australia, is episodically impacted by tropical cyclones. During 2015, the region was hit by a category 3 cyclone, "severe tropical cyclone Olywn," leading to the formation of a black sludge in an intertidal zone harboring microbial mats and microbialites. Upon returning to the impacted site 12 months later, the black sludge deposit was still recognizable between the microbialite columns and mucilaginous cobbles near the shoreline in the impacted area. Metatranscriptomic and organic geochemical analyses were carried out on the cyclone-derived materials and impacted microbial mat communities to unravel the structure, function, and potential preservation of these deposits following a tropical cyclone. It was found that samples derived from the black sludge contained low relative abundances of cyanobacteria but had higher proportions of heterotrophic and anaerobic microorganisms (e.g., methanogens and sulfate-reducing bacteria). Increased metabolic activity by these microorganisms (e.g., sulfate reduction and organic matter degradation) is thought to drive calcium carbonate precipitation and helps in mat preservation. Comparison of the aliphatic biomarker by gas chromatography-mass spectrometry (GC-MS) analyses showed that C25 highly branched isoprenoid (HBI) alkenes were significantly higher in the cyclone-derived materials attributed to the relocation of subtidal sediments containing HBI-producing diatom communities by the tropical cyclone. Raney nickel desulfurization of the polar fraction extracted from a mucilaginous cobble revealed sulfur-bound hopanoids and a series of benzohopanes. The presence of these compounds could be indicative of microbial matter that has been influenced by the tropical cyclone which may have caused elevated levels of water column anoxia promoting increased sulfurization of the organic matter to occur.
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Affiliation(s)
- Matthew A Campbell
- WA-Organic Isotope Geochemistry Centre, The Institute for Geoscience Research, School of Earth and Planetary Sciences, Curtin University, Perth, WA, Australia
| | - Marco J L Coolen
- WA-Organic Isotope Geochemistry Centre, The Institute for Geoscience Research, School of Earth and Planetary Sciences, Curtin University, Perth, WA, Australia
| | - Pieter T Visscher
- Departments of Marine Sciences and Geoscience, University of Connecticut, Storrs, CT, USA
- Australian Centre for Astrobiology, University of New South Wales, Sydney, NSW, Australia
| | - Therese Morris
- Applied Geology, Curtin University, Perth, WA, Australia
| | - Kliti Grice
- WA-Organic Isotope Geochemistry Centre, The Institute for Geoscience Research, School of Earth and Planetary Sciences, Curtin University, Perth, WA, Australia
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43
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Valença CAS, Barbosa AAT, Souto EB, Caramão EB, Jain S. Volatile Nitrogenous Compounds from Bacteria: Source of Novel Bioactive Compounds. Chem Biodivers 2021; 18:e2100549. [PMID: 34643327 DOI: 10.1002/cbdv.202100549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 09/27/2021] [Indexed: 11/08/2022]
Abstract
Bacteria can produce nitrogenous compounds via both primary and secondary metabolic processes. Many bacterial volatile nitrogenous compounds produced during the secondary metabolism have been identified and reported for their antioxidant, antibacterial, antifungal, algicidal and antitumor activities. The production of these nitrogenous compounds depends on several factors, including the composition of culture media, growth conditions, and even the organic solvent used for their extraction, thus requiring their identification in specific conditions. In this review, we describe the volatile nitrogenous compounds produced by bacteria especially focusing on their antimicrobial activity. We concentrate on azo-compounds mainly pyrazines and pyrrolo-pyridines reported for their activity against several microorganisms. Whenever significant, extraction and identification methods of these compounds are also mentioned and discussed. To the best of our knowledge, this is first review describing volatile nitrogenous compounds from bacteria focusing on their biological activity.
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Affiliation(s)
- Camilla A S Valença
- Programa de Pós-Graduação em Biotecnologia Industrial, Universidade Tiradentes, Aracaju, Sergipe, Brazil
| | - Ana A T Barbosa
- Department of Morphology, Universidade Federal de Sergipe, São Cristóvão, Sergipe, Brazil
| | - Eliana B Souto
- CEB - Center of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Elina B Caramão
- Programa de Pós-Graduação em Biotecnologia Industrial, Universidade Tiradentes, Aracaju, Sergipe, Brazil.,Instituto Nacional de Ciência e Tecnologia - Energia e Ambiente, Universidade Federal da Bahia, Salvador, Bahia, Brazil
| | - Sona Jain
- Programa de Pós-Graduação em Biotecnologia Industrial, Universidade Tiradentes, Aracaju, Sergipe, Brazil
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Priyadarshini P, Choudhury S, Tilgam J, Bharati A, Sreeshma N. Nitrogen fixing cereal: A rising hero towards meeting food security. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2021; 167:912-920. [PMID: 34547550 DOI: 10.1016/j.plaphy.2021.09.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 09/05/2021] [Accepted: 09/08/2021] [Indexed: 06/13/2023]
Abstract
Nitrogen serves as one of the primary components of major biomolecules and thus extends a significant contribution to crop growth and yield. But the inability of plants to utilize freely available atmospheric N2 makes the whole agricultural system dependent on chemical fertilizers, which incur significant input cost to supplement required quantities of nitrogen to crops. Only bacteria and archaea have been gifted with the power of drawing free N2 from air to convert them into NH3, which is one of the two utilizable forms of nitrogen taken up by plants. Legumes, the only family of crops, can engage themselves in symbiotic nitrogen fixation where they establish a mutualistic relationship with nitrogen-fixing bacteria and in turn, can waive off the necessity of adding nitrogen fertilizers. Sincere effort, therefore, has been undertaken to incorporate this capability of nitrogen-fixation into non-legume crops, especially cereals which make up a vital portion in the food basket. Biotechnological interventions have also played important role in providing nitrogen fixing trait to non-legumes. This review takes up an effort to look into and accumulate all the important updates to date regarding nitrogen-fixing non-legumes with a special focus on cereals, which is one of the most important future goals in the field of science in the present era.
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Affiliation(s)
- Parichita Priyadarshini
- ICAR-Crop Improvement Division, Indian Grassland and Fodder Research Institute, Jhansi, U.P., 284003, India
| | - Sharani Choudhury
- ICAR - National Institute for Plant Biotechnology, Indian Agricultural Research Institute, New Delhi, 110012, India
| | - Jyotsana Tilgam
- ICAR- National Bureau of Agriculturally Important Microorganisms, Maunath Bhanjan, U.P., 274103, India.
| | - Alka Bharati
- ICAR-Central Agroforestry Research Institute, Jhansi, U.P., 284003, India
| | - N Sreeshma
- ICAR - National Institute for Plant Biotechnology, Indian Agricultural Research Institute, New Delhi, 110012, India
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Waite CJ, Lindström Battle A, Bennett MH, Carey MR, Hong CK, Kotta-Loizou I, Buck M, Schumacher J. Resource Allocation During the Transition to Diazotrophy in Klebsiella oxytoca. Front Microbiol 2021; 12:718487. [PMID: 34434180 PMCID: PMC8381380 DOI: 10.3389/fmicb.2021.718487] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 07/12/2021] [Indexed: 11/13/2022] Open
Abstract
Free-living nitrogen-fixing bacteria can improve growth yields of some non-leguminous plants and, if enhanced through bioengineering approaches, have the potential to address major nutrient imbalances in global crop production by supplementing inorganic nitrogen fertilisers. However, nitrogen fixation is a highly resource-costly adaptation and is de-repressed only in environments in which sources of reduced nitrogen are scarce. Here we investigate nitrogen fixation (nif) gene expression and nitrogen starvation response signaling in the model diazotroph Klebsiella oxytoca (Ko) M5a1 during ammonium depletion and the transition to growth on atmospheric N2. Exploratory RNA-sequencing revealed that over 50% of genes were differentially expressed under diazotrophic conditions, among which the nif genes are among the most highly expressed and highly upregulated. Isotopically labelled QconCAT standards were designed for multiplexed, absolute quantification of Nif and nitrogen-stress proteins via multiple reaction monitoring mass spectrometry (MRM-MS). Time-resolved Nif protein concentrations were indicative of bifurcation in the accumulation rates of nitrogenase subunits (NifHDK) and accessory proteins. We estimate that the nitrogenase may account for more than 40% of cell protein during diazotrophic growth and occupy approximately half the active ribosome complement. The concentrations of free amino acids in nitrogen-starved cells were insufficient to support the observed rates of Nif protein expression. Total Nif protein accumulation was reduced 10-fold when the NifK protein was truncated and nitrogenase catalysis lost (nifK1–1203), implying that reinvestment of de novo fixed nitrogen is essential for further nif expression and a complete diazotrophy transition. Several amino acids accumulated in non-fixing ΔnifLA and nifK1–1203 mutants, while the rest remained highly stable despite prolonged N starvation. Monitoring post-translational uridylylation of the PII-type signaling proteins GlnB and GlnK revealed distinct nitrogen regulatory roles in Ko M5a1. GlnK uridylylation was persistent throughout the diazotrophy transition while a ΔglnK mutant exhibited significantly reduced Nif expression and nitrogen fixation activity. Altogether, these findings highlight quantitatively the scale of resource allocation required to enable the nitrogen fixation adaptation to take place once underlying signaling processes are fulfilled. Our work also provides an omics-level framework with which to model nitrogen fixation in free-living diazotrophs and inform rational engineering strategies.
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Affiliation(s)
- Christopher J Waite
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | | | - Mark H Bennett
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Matthew R Carey
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Chun K Hong
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Ioly Kotta-Loizou
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Martin Buck
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Jörg Schumacher
- Department of Life Sciences, Imperial College London, London, United Kingdom
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46
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Schnabel T, Sattely E. Engineering Posttranslational Regulation of Glutamine Synthetase for Controllable Ammonia Production in the Plant Symbiont Azospirillum brasilense. Appl Environ Microbiol 2021; 87:e0058221. [PMID: 33962983 PMCID: PMC8231714 DOI: 10.1128/aem.00582-21] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 04/27/2021] [Indexed: 11/20/2022] Open
Abstract
Nitrogen requirements for modern agriculture far exceed the levels of bioavailable nitrogen in most arable soils. As a result, the addition of nitrogen fertilizer is necessary to sustain productivity and yields, especially for cereal crops, the planet's major calorie suppliers. Given the unsustainability of industrial fertilizer production and application, engineering biological nitrogen fixation directly at the roots of plants has been a grand challenge for biotechnology. Here, we designed and tested a potentially broadly applicable metabolic engineering strategy for the overproduction of ammonia in the diazotrophic symbiont Azospirillum brasilense. Our approach is based on an engineered unidirectional adenylyltransferase (uAT) that posttranslationally modifies and deactivates glutamine synthetase (GS), a key regulator of nitrogen metabolism in the cell. We show that this circuit can be controlled inducibly, and we leveraged the inherent self-contained nature of our posttranslational approach to demonstrate that multicopy redundancy can improve strain evolutionary stability. uAT-engineered Azospirillum is capable of producing ammonia at rates of up to 500 μM h-1 unit of OD600 (optical density at 600 nm)-1. We demonstrated that when grown in coculture with the model monocot Setaria viridis, these strains increase the biomass and chlorophyll content of plants up to 54% and 71%, respectively, relative to the wild type (WT). Furthermore, we rigorously demonstrated direct transfer of atmospheric nitrogen to extracellular ammonia and then plant biomass using isotopic labeling: after 14 days of cocultivation with engineered uAT strains, 9% of chlorophyll nitrogen in Setaria seedlings was derived from diazotrophically fixed dinitrogen, whereas no nitrogen was incorporated in plants cocultivated with WT controls. This rational design for tunable ammonia overproduction is modular and flexible, and we envision that it could be deployable in a consortium of nitrogen-fixing symbiotic diazotrophs for plant fertilization. IMPORTANCE Nitrogen is the most limiting nutrient in modern agriculture. Free-living diazotrophs, such as Azospirillum, are common colonizers of cereal grasses and have the ability to fix nitrogen but natively do not release excess ammonia. Here, we used a rational engineering approach to generate ammonia-excreting strains of Azospirillum. Our design features posttranslational control of highly conserved central metabolism, enabling tunability and flexibility of circuit placement. We found that our strains promote the growth and health of the model grass S. viridis and rigorously demonstrated that in comparison to WT controls, our engineered strains can transfer nitrogen from 15N2 gas to plant biomass. Unlike previously reported ammonia-producing mutants, our rationally designed approach easily lends itself to further engineering opportunities and has the potential to be broadly deployable.
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Affiliation(s)
- Tim Schnabel
- Department of Bioengineering, Stanford University, Stanford, California, USA
| | - Elizabeth Sattely
- Department of Chemical Engineering, Stanford University and HHMI, Stanford, California, USA
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47
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Haskett TL, Knights HE, Jorrin B, Mendes MD, Poole PS. A Simple in situ Assay to Assess Plant-Associative Bacterial Nitrogenase Activity. Front Microbiol 2021; 12:690439. [PMID: 34248916 PMCID: PMC8261070 DOI: 10.3389/fmicb.2021.690439] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 05/25/2021] [Indexed: 11/23/2022] Open
Abstract
Assessment of plant-associative bacterial nitrogen (N) fixation is crucial for selection and development of elite diazotrophic inoculants that could be used to supply cereal crops with nitrogen in a sustainable manner. Although diazotrophic bacteria possess diverse oxygen tolerance mechanisms, most require a sub 21% oxygen environment to achieve optimal stability and function of the N-fixing catalyst nitrogenase. Consequently, assessment of N fixation is routinely carried out on “free-living” bacteria grown in the absence of a host plant and such experiments may not accurately divulge activity in the rhizosphere where the availability and forms of nutrients such as carbon and N, which are key regulators of N fixation, may vary widely. Here, we present a modified in situ acetylene reduction assay (ARA), utilizing the model cereal barley as a host to comparatively assess nitrogenase activity in diazotrophic bacteria. The assay is rapid, highly reproducible, applicable to a broad range of diazotrophs, and can be performed with simple equipment commonly found in most laboratories that investigate plant-microbe interactions. Thus, the assay could serve as a first point of order for high-throughput identification of elite plant-associative diazotrophs.
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Affiliation(s)
- Timothy L Haskett
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Hayley E Knights
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Beatriz Jorrin
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Marta D Mendes
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Philip S Poole
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
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Bueno Batista M, Brett P, Appia-Ayme C, Wang YP, Dixon R. Disrupting hierarchical control of nitrogen fixation enables carbon-dependent regulation of ammonia excretion in soil diazotrophs. PLoS Genet 2021; 17:e1009617. [PMID: 34111137 PMCID: PMC8219145 DOI: 10.1371/journal.pgen.1009617] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 06/22/2021] [Accepted: 05/23/2021] [Indexed: 12/14/2022] Open
Abstract
The energetic requirements for biological nitrogen fixation necessitate stringent regulation of this process in response to diverse environmental constraints. To ensure that the nitrogen fixation machinery is expressed only under appropriate physiological conditions, the dedicated NifL-NifA regulatory system, prevalent in Proteobacteria, plays a crucial role in integrating signals of the oxygen, carbon and nitrogen status to control transcription of nitrogen fixation (nif) genes. Greater understanding of the intricate molecular mechanisms driving transcriptional control of nif genes may provide a blueprint for engineering diazotrophs that associate with cereals. In this study, we investigated the properties of a single amino acid substitution in NifA, (NifA-E356K) which disrupts the hierarchy of nif regulation in response to carbon and nitrogen status in Azotobacter vinelandii. The NifA-E356K substitution enabled overexpression of nitrogenase in the presence of excess fixed nitrogen and release of ammonia outside the cell. However, both of these properties were conditional upon the nature of the carbon source. Our studies reveal that the uncoupling of nitrogen fixation from its assimilation is likely to result from feedback regulation of glutamine synthetase, allowing surplus fixed nitrogen to be excreted. Reciprocal substitutions in NifA from other Proteobacteria yielded similar properties to the A. vinelandii counterpart, suggesting that this variant protein may facilitate engineering of carbon source-dependent ammonia excretion amongst diverse members of this family.
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Affiliation(s)
| | - Paul Brett
- Department of Metabolic Biology, John Innes Centre, Norwich, United Kingdom
| | - Corinne Appia-Ayme
- Department of Molecular Microbiology, John Innes Centre, Norwich, United Kingdom
| | - Yi-Ping Wang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences & School of Advanced Agricultural Sciences, Peking University, Beijing, China
| | - Ray Dixon
- Department of Molecular Microbiology, John Innes Centre, Norwich, United Kingdom
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49
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Udvardi M, Below FE, Castellano MJ, Eagle AJ, Giller KE, Ladha JK, Liu X, Maaz TM, Nova-Franco B, Raghuram N, Robertson GP, Roy S, Saha M, Schmidt S, Tegeder M, York LM, Peters JW. A Research Road Map for Responsible Use of Agricultural Nitrogen. FRONTIERS IN SUSTAINABLE FOOD SYSTEMS 2021. [DOI: 10.3389/fsufs.2021.660155] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Nitrogen (N) is an essential but generally limiting nutrient for biological systems. Development of the Haber-Bosch industrial process for ammonia synthesis helped to relieve N limitation of agricultural production, fueling the Green Revolution and reducing hunger. However, the massive use of industrial N fertilizer has doubled the N moving through the global N cycle with dramatic environmental consequences that threaten planetary health. Thus, there is an urgent need to reduce losses of reactive N from agriculture, while ensuring sufficient N inputs for food security. Here we review current knowledge related to N use efficiency (NUE) in agriculture and identify research opportunities in the areas of agronomy, plant breeding, biological N fixation (BNF), soil N cycling, and modeling to achieve responsible, sustainable use of N in agriculture. Amongst these opportunities, improved agricultural practices that synchronize crop N demand with soil N availability are low-hanging fruit. Crop breeding that targets root and shoot physiological processes will likely increase N uptake and utilization of soil N, while breeding for BNF effectiveness in legumes will enhance overall system NUE. Likewise, engineering of novel N-fixing symbioses in non-legumes could reduce the need for chemical fertilizers in agroecosystems but is a much longer-term goal. The use of simulation modeling to conceptualize the complex, interwoven processes that affect agroecosystem NUE, along with multi-objective optimization, will also accelerate NUE gains.
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50
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Sayavedra L, Li T, Bueno Batista M, Seah BKB, Booth C, Zhai Q, Chen W, Narbad A. Desulfovibrio diazotrophicus sp. nov., a sulfate-reducing bacterium from the human gut capable of nitrogen fixation. Environ Microbiol 2021; 23:3164-3181. [PMID: 33876566 DOI: 10.1111/1462-2920.15538] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 03/24/2021] [Accepted: 04/16/2021] [Indexed: 12/13/2022]
Abstract
Sulfate-reducing bacteria (SRB) are widespread in human guts, yet their expansion has been linked to colonic diseases. We report the isolation, sequencing and physiological characterization of strain QI0027T , a novel SRB species belonging to the class Desulfovibrionia. Metagenomic sequencing of stool samples from 45 Chinese individuals, and comparison with 1690 Desulfovibrionaceae metagenome-assembled genomes recovered from humans of diverse geographic locations, revealed the presence of QI0027T in 22 further individuals. QI0027T encoded nitrogen fixation genes and based on the acetylene reduction assay, actively fixed nitrogen. Transcriptomics revealed that QI0027T overexpressed 42 genes in nitrogen-limiting conditions compared to cultures supplemented with ammonia, including genes encoding nitrogenases, a urea uptake system and the urease complex. Reanalyses of 835 public stool metatranscriptomes showed that nitrogenase genes from Desulfovibrio bacteria were expressed in six samples suggesting that nitrogen fixation might be active in the gut environment. Although frequently thought of as a nutrient-rich environment, nitrogen fixation can occur in the human gut. Animals are often nitrogen limited and have evolved diverse strategies to capture biologically active nitrogen, ranging from amino acid transporters to stable associations with beneficial microbes that provide fixed nitrogen. QI0027T is the first Desulfovibrio human isolate for which nitrogen fixation has been demonstrated, suggesting that some sulfate-reducing bacteria could also play a role in the availability of nitrogen in the gut.
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Affiliation(s)
- Lizbeth Sayavedra
- Gut Health and Microbes, Quadram Institute Bioscience, Norwich Research Park, Norwich, UK
| | - Tianqi Li
- Gut Health and Microbes, Quadram Institute Bioscience, Norwich Research Park, Norwich, UK.,State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, China
| | - Marcelo Bueno Batista
- Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Brandon K B Seah
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Catherine Booth
- Gut Health and Microbes, Quadram Institute Bioscience, Norwich Research Park, Norwich, UK
| | - Qixiao Zhai
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, China
| | - Wei Chen
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, China
| | - Arjan Narbad
- Gut Health and Microbes, Quadram Institute Bioscience, Norwich Research Park, Norwich, UK
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