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Ito Y, Yoshidome D, Hidaka M, Araki Y, Ito K, Kosono S, Nishiyama M. Improvement of the nitrogenase activity in Escherichia coli that expresses the nitrogen fixation-related genes from Azotobacter vinelandii. Biochem Biophys Res Commun 2024; 728:150345. [PMID: 38971001 DOI: 10.1016/j.bbrc.2024.150345] [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: 04/09/2024] [Revised: 06/27/2024] [Accepted: 07/02/2024] [Indexed: 07/08/2024]
Abstract
The transfer of nitrogen fixation (nif) genes from diazotrophs to non-diazotrophic hosts is of increasing interest for engineering biological nitrogen fixation. A recombinant Escherichia coli strain expressing Azotobacter vinelandii 18 nif genes (nifHDKBUSVQENXYWZMF, nifiscA, and nafU) were previously constructed and showed nitrogenase activity. In the present study, we constructed several E. coli strain derivatives in which all or some of the 18 nif genes were additionally integrated into the fliK locus of the chromosome in various combinations. E. coli derivatives with the chromosomal integration of nifiscA, nifU, and nifS, which are involved in the biosynthesis of the [4Fe-4S] cluster of dinitrogenase reductase, exhibited enhanced nitrogenase activity. We also revealed that overexpression of E. coli fldA and ydbK, which encode flavodoxin and flavodoxin-reducing enzyme, respectively, enhanced nitrogenase activity, likely by facilitating electron transfer to dinitrogenase reductase. The additional expression of nifM, putatively involved in maturation of dinitrogenase reductase, further enhanced nitrogenase activity and the amount of soluble NifH. By combining these factors, we successfully improved nitrogenase activity 10-fold.
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Affiliation(s)
- Yusuke Ito
- Agro-Biotechnology Research Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan; Research & Development Division, Kikkoman Corporation, 338 Noda, Noda, Chiba, 278-0037, Japan
| | - Daisuke Yoshidome
- Agro-Biotechnology Research Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Makoto Hidaka
- Agro-Biotechnology Research Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Yasuko Araki
- Research & Development Division, Kikkoman Corporation, 338 Noda, Noda, Chiba, 278-0037, Japan
| | - Kotaro Ito
- Research & Development Division, Kikkoman Corporation, 338 Noda, Noda, Chiba, 278-0037, Japan
| | - Saori Kosono
- Agro-Biotechnology Research Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan; Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Makoto Nishiyama
- Agro-Biotechnology Research Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan; Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
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2
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Gao M, Andrews J, Armin G, Chakraborty S, Zehr JP, Inomura K. Rapid mode switching facilitates the growth of Trichodesmium: A model analysis. iScience 2024; 27:109906. [PMID: 38947530 PMCID: PMC11214483 DOI: 10.1016/j.isci.2024.109906] [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: 07/06/2023] [Revised: 02/28/2024] [Accepted: 05/02/2024] [Indexed: 07/02/2024] Open
Abstract
Trichodesmium is one of the dominant dinitrogen (N2) fixers in the ocean, influencing global carbon and nitrogen cycles through biochemical reactions. Although its photosynthetic activity fluctuates rapidly, the physiological or ecological advantage of this fluctuation is unclear. We develop a metabolic model of Trichodesmium that can perform daytime N2 fixation. We examined (1) the effect of the duration of switches between photosynthetic and non-photosynthetic cellular states and (2) the effect of the presence and absence of N2 fixation in photosynthetic states. Results show that a rapid switch between photosynthetic and non-photosynthetic states increases Trichodesmium growth rates by improving metabolic efficiencies due to an improved balance of C and N metabolism. This provides a strategy for previous paradoxical observations that all Trichodesmium cells can contain nitrogenase. This study reveals the importance of fluctuating photosynthetic activity and provides a mechanism for daytime N2 fixation that allows Trichodesmium to fix N2 aerobically in the global ocean.
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Affiliation(s)
- Meng Gao
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Jamal Andrews
- Biological and Environmental Sciences Graduate Program, University of Rhode Island, Kingston, RI, USA
| | - Gabrielle Armin
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Subhendu Chakraborty
- Systems Ecology Group, Leibniz Centre for Tropical Marine Research (ZMT), Bremen, Germany
| | - Jonathan P. Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
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3
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He H, Zheng W, Xiao S, Gong L, Li H, Zhou K, Zhang L, Tu Q, Zhu YZ, Zhang Y. Deciphering the Nitrogen Fixation Gene Cluster in Vibrio natriegens: A Study on Optimized Expression and Application of Nitrogenase. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2024; 72:12618-12629. [PMID: 38778776 DOI: 10.1021/acs.jafc.4c01232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Microbial nitrogen fixation presents a viable alternative to chemical fertilizers, yet the limited colonization and specificity of naturally occurring nitrogen-fixing microorganisms present significant challenges to their widespread application. In this study, we identified a nitrogen fixation gene cluster (VNnif) in Vibrio natriegens (VN) and tested its nitrogenase activity through the acetylene reduction assay. We investigated the potential utilization of nitrogenase by incorporating the nitrogenase gene cluster from VN into plant growth-promoting rhizosphere bacteria Pseudomonas protegens CHA0 and enhancing its activity to 48.16 nmol C2H2/mg/h through promoter replacement and cluster rearrangement. The engineered strain CHA0-PVNnif was found to positively impact the growth of Arabidopsis thaliana col-0 and Triticum aestivum L. (wheat). This study expanded the role of plant growth-promoting rhizobacteria (PGPR) and provided a research foundation for enhancing nitrogenase activity.
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Affiliation(s)
- Haocheng He
- CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Weijin Zheng
- CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- College of Life and Geographic Sciences, Kashi University, Kashi 844099, China
| | - Shuai Xiao
- CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Liang Gong
- CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - He Li
- CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- School of Pharmacy, Faculty of Medicine, Macau University of Science and Technology, Macau SAR 999078, China
| | - Kexuan Zhou
- CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- School of Pharmacy, Faculty of Medicine, Macau University of Science and Technology, Macau SAR 999078, China
| | - Letian Zhang
- CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- State Key Lab of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau 999078, China
| | - Qiang Tu
- CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Yi Zhun Zhu
- School of Pharmacy, Faculty of Medicine, Macau University of Science and Technology, Macau SAR 999078, China
- State Key Lab of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau 999078, China
| | - Youming Zhang
- CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
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4
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Danial AW, Basset RA. Amelioration of NaCl stress on germination, growth, and nitrogen fixation of Vicia faba at isosmotic Na-Ca combinations and Rhizobium. PLANTA 2024; 259:69. [PMID: 38340188 PMCID: PMC10858841 DOI: 10.1007/s00425-024-04343-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Accepted: 01/12/2024] [Indexed: 02/12/2024]
Abstract
MAIN CONCLUSION The Na+/Ca2+ ratio of 1/5 ameliorated the inhibitory action of NaCl and improved the germination and growth of Vicia faba. Addition of Rhizobium also enhanced nodulation and nitrogen fixation. Casting light upon the impact of salinity stress on growth and nitrogen fixation of Vicia faba supplemented with Rhizobium has been traced in this work. How Ca2+ antagonizes Na+ toxicity and osmotic stress of NaCl was also targeted in isosmotic combinations of NaCl and CaCl2 having various Na+:Ca2+ ratios. Growth of Vicia faba (cultivar Giza 3) was studied at two stages: germination and seedling. At both experiments, seeds or seedlings were exposed to successively increasing salinity levels (0, 50, 100, 150, and 200 mM NaCl) as well as isosmotic combinations of NaCl and CaCl2 (Na+:Ca2+ of 1:1, 1:5, 1:10, 1:15, 1:18, and 1: 20), equivalent to 150 mM NaCl. Inocula of the local nitrogen-fixing bacteria, Rhizobium leguminosarum (OP715892) were supplemented at both stages. NaCl salinity exerted a negative impact on growth and metabolism of Vicia faba; inhibition was proportional with increasing salinity level up to the highest level of 200 mM. Seed germination, shoot and root lengths, fresh and dry weights, chlorophyll content, and nodules (number, weight, leghemoglobin, respiration, and nitrogenase activity) were inhibited by salinity. Ca2+ substitution for Na+, particularly at a Na/Ca ratio of 1:5, was stimulatory to almost all parameters at both stages. Statistical correlations between salinity levels and Na/Ca combinations proved one of the four levels (strong- or weak positive, strong- or weak negative) with most of the investigated parameters, depending on the parameter.
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Affiliation(s)
- Amal W Danial
- Botany and Microbiology Department, Faculty of Science, Assiut University, Assiut, 71516, Egypt.
| | - Refat Abdel Basset
- Botany and Microbiology Department, Faculty of Science, Assiut University, Assiut, 71516, Egypt
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5
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Fernández-Juárez V, Hallstrøm S, Pacherres CO, Wang J, Coll-Garcia G, Kühl M, Riemann L. Biofilm formation and cell plasticity drive diazotrophy in an anoxygenic phototrophic bacterium. Appl Environ Microbiol 2023; 89:e0102723. [PMID: 37882569 PMCID: PMC10686084 DOI: 10.1128/aem.01027-23] [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: 06/23/2023] [Accepted: 09/14/2023] [Indexed: 10/27/2023] Open
Abstract
IMPORTANCE The contribution of non-cyanobacterial diazotrophs (NCDs) to total N2 fixation in the marine water column is unknown, but their importance is likely constrained by the limited availability of dissolved organic matter and low O2 conditions. Light could support N2 fixation and growth by NCDs, yet no examples from bacterioplankton exist. In this study, we show that the phototrophic NCD, Rhodopseudomonas sp. BAL398, which is a member of the diazotrophic community in the surface waters of the Baltic Sea, can utilize light. Our study highlights the significance of biofilm formation for utilizing light and fixing N2 under oxic conditions and the role of cell plasticity in regulating these processes. Our findings have implications for the general understanding of the ecology and importance of NCDs in marine waters.
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Affiliation(s)
- Víctor Fernández-Juárez
- Marine Biological Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Søren Hallstrøm
- Marine Biological Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen, Denmark
| | - Cesar O. Pacherres
- Marine Biological Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Jiaqi Wang
- Marine Biological Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Guillem Coll-Garcia
- Microbiology, Biology Department, University of the Balearic Islands, Palma de Mallorca, Spain
- Environmental Microbiology Group, Mediterranean Institute for Advanced Studies (CSIC-UIB), Esporles, Spain
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Lasse Riemann
- Marine Biological Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
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6
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Saad MH, Sidkey NM, El-Fakharany EM. Identification and statistical optimization of a novel alginate polymer extracted from newly isolated Synechocystis algini MNE ON864447 with antibacterial activity. Microb Cell Fact 2023; 22:229. [PMID: 37932753 PMCID: PMC10629183 DOI: 10.1186/s12934-023-02240-w] [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: 09/09/2023] [Accepted: 10/28/2023] [Indexed: 11/08/2023] Open
Abstract
Cyanobacteria are a potential source of promising secondary metabolites with different biological activities, including antibacterial, antiviral, antifungal, antiprotozoal, and anticancer activities. To combat the emergence of antibiotic resistance, there is an urgent requirement for new drugs, and cyanobacteria metabolites can constitute alternative new antibacterial medication. The chemical complexity of their exopolysaccharides indicates that they have the potential to be bioactive molecules with many biological activities. The present study aimed to produce and optimise a novel alginate polymer from a newly isolated cyanobacterium, S. algini MNE ON864447, in addition to its promising antibacterial activity. We successfully isolated a new cyanobacterium strain, S. algini MNE ON864447 from the Nile River, which produces alginate as an extracellular polymeric substance. The isolated cyanobacterial alginate was identified using a set of tests, including FTIR, TLC, HPLC, GC-MS, and 1H NMR. Plackett-Burman statistical design showed that working volume (X1), the incubation period (X2), and inoculum size (X3) are the most significant variables affecting the production of alginate. The highest alginate production (3.57 g/L) was obtained using 4% inoculum size in 400 mL medium/L conical flask after 20 days of the incubation period. The extracted alginate showed potent antibacterial activity against both Gram-negative and Gram-positive bacteria and Streptococcus mutants (NCTC10449) are the most sensitive tested pathogen for purified cyanobacterial alginate with inhibition zone diameters of 34 ± 0.1 mm at 10 mg/mL of purified alginate while Vibro cholera (NCTC 8021) the lowest sensitive one and showed inhibition zone diameters of 22.5 ± 0.05 mm at the same cyanobacterial alginate concentration. This antibacterial activity is a critical step in the development of antibacterial drugs and presents a new challenge to fight against multi-resistant bacteria.
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Affiliation(s)
- Mabroka H Saad
- Protein Research Department, Genetic Engineering and Biotechnology Research Institute (GEBRI), City of Scientific Research andTechnological Applications (SRTA-City), New Borg AL Arab, Alexandria, Egypt
- Botany & Microbiology Department, Faculty of Science, Al-Azhar University (Girls Branch), Cairo, Egypt
| | - Nagwa M Sidkey
- Botany & Microbiology Department, Faculty of Science, Al-Azhar University (Girls Branch), Cairo, Egypt
| | - Esmail M El-Fakharany
- Protein Research Department, Genetic Engineering and Biotechnology Research Institute (GEBRI), City of Scientific Research andTechnological Applications (SRTA-City), New Borg AL Arab, Alexandria, Egypt.
- Pharmaceutical and Fermentation Industries Development Centre (PFIDC), City of Scientific Research and Technological Applications (SRTA-City), New Borg Al-Arab, Alexandria, Egypt.
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7
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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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8
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Llamas A, Leon-Miranda E, Tejada-Jimenez M. Microalgal and Nitrogen-Fixing Bacterial Consortia: From Interaction to Biotechnological Potential. PLANTS (BASEL, SWITZERLAND) 2023; 12:2476. [PMID: 37447037 DOI: 10.3390/plants12132476] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 06/15/2023] [Accepted: 06/26/2023] [Indexed: 07/15/2023]
Abstract
Microalgae are used in various biotechnological processes, such as biofuel production due to their high biomass yields, agriculture as biofertilizers, production of high-value-added products, decontamination of wastewater, or as biological models for carbon sequestration. The number of these biotechnological applications is increasing, and as such, any advances that contribute to reducing costs and increasing economic profitability can have a significant impact. Nitrogen fixing organisms, often called diazotroph, also have great biotechnological potential, mainly in agriculture as an alternative to chemical fertilizers. Microbial consortia typically perform more complex tasks than monocultures and can execute functions that are challenging or even impossible for individual strains or species. Interestingly, microalgae and diazotrophic organisms are capable to embrace different types of symbiotic associations. Certain corals and lichens exhibit this symbiotic relationship in nature, which enhances their fitness. However, this relationship can also be artificially created in laboratory conditions with the objective of enhancing some of the biotechnological processes that each organism carries out independently. As a result, the utilization of microalgae and diazotrophic organisms in consortia is garnering significant interest as a potential alternative for reducing production costs and increasing yields of microalgae biomass, as well as for producing derived products and serving biotechnological purposes. This review makes an effort to examine the associations of microalgae and diazotrophic organisms, with the aim of highlighting the potential of these associations in improving various biotechnological processes.
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Affiliation(s)
- Angel Llamas
- Department of Biochemistry and Molecular Biology, Campus de Rabanales and Campus Internacional de Excelencia Agroalimentario (CeiA3), Edificio Severo Ochoa, University of Córdoba, 14071 Córdoba, Spain
| | - Esperanza Leon-Miranda
- Department of Biochemistry and Molecular Biology, Campus de Rabanales and Campus Internacional de Excelencia Agroalimentario (CeiA3), Edificio Severo Ochoa, University of Córdoba, 14071 Córdoba, Spain
| | - Manuel Tejada-Jimenez
- Department of Biochemistry and Molecular Biology, Campus de Rabanales and Campus Internacional de Excelencia Agroalimentario (CeiA3), Edificio Severo Ochoa, University of Córdoba, 14071 Córdoba, Spain
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9
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Alleman AB, Peters JW. Mechanisms for Generating Low Potential Electrons across the Metabolic Diversity of Nitrogen-Fixing Bacteria. Appl Environ Microbiol 2023; 89:e0037823. [PMID: 37154716 PMCID: PMC10231201 DOI: 10.1128/aem.00378-23] [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] [Indexed: 05/10/2023] Open
Abstract
The availability of fixed nitrogen is a limiting factor in the net primary production of all ecosystems. Diazotrophs overcome this limit through the conversion of atmospheric dinitrogen to ammonia. Diazotrophs are phylogenetically diverse bacteria and archaea that exhibit a wide range of lifestyles and metabolisms, including obligate anaerobes and aerobes that generate energy through heterotrophic or autotrophic metabolisms. Despite the diversity of metabolisms, all diazotrophs use the same enzyme, nitrogenase, to reduce N2. Nitrogenase is an O2-sensitive enzyme that requires a high amount of energy in the form of ATP and low potential electrons carried by ferredoxin (Fd) or flavodoxin (Fld). This review summarizes how the diverse metabolisms of diazotrophs utilize different enzymes to generate low potential reducing equivalents for nitrogenase catalysis. These enzymes include substrate-level Fd oxidoreductases, hydrogenases, photosystem I or other light-driven reaction centers, electron bifurcating Fix complexes, proton motive force-driven Rnf complexes, and Fd:NAD(P)H oxidoreductases. Each of these enzymes is critical for generating low potential electrons while simultaneously integrating the native metabolism to balance nitrogenase's overall energy needs. Understanding the diversity of electron transport systems to nitrogenase in various diazotrophs will be essential to guide future engineering strategies aimed at expanding the contributions of biological nitrogen fixation in agriculture.
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Affiliation(s)
- Alexander B. Alleman
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA
| | - John W. Peters
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
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10
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Darnajoux R, Inomura K, Zhang X. A diazotrophy-ammoniotrophy dual growth model for the sulfate reducing bacterium Desulfovibrio vulgaris var. Hildenborough. Comput Struct Biotechnol J 2023; 21:3136-3148. [PMID: 37293241 PMCID: PMC10244686 DOI: 10.1016/j.csbj.2023.05.007] [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: 01/31/2023] [Revised: 05/04/2023] [Accepted: 05/05/2023] [Indexed: 06/10/2023] Open
Abstract
Sulfate reducing bacteria (SRB) comprise one of the few prokaryotic groups in which biological nitrogen fixation (BNF) is common. Recent studies have highlighted SRB roles in N cycling, particularly in oligotrophic coastal and benthic environments where they could contribute significantly to N input. Most studies of SRB have focused on sulfur cycling and SRB growth models have primarily aimed at understanding the effects of electron sources, with N usually provided as fixed-N (nitrate, ammonium). Mechanistic links between SRB nitrogen-fixing metabolism and growth are not well understood, particularly in environments where fixed-N fluctuates. Here, we investigate diazotrophic growth of the model sulfate reducer Desulfovibrio vulgaris var. Hildenborough under anaerobic heterotrophic conditions and contrasting N availabilities using a simple cellular model with dual ammoniotrophic and diazotrophic modes. The model was calibrated using batch culture experiments with varying initial ammonium concentrations (0-3000 µM) and acetylene reduction assays of BNF activity. The model confirmed the preferential usage of ammonium over BNF for growth and successfully reproduces experimental data, with notably clear bi-phasic growth curves showing an initial ammoniotrophic phase followed by onset of BNF. Our model enables quantification of the energetic cost of each N acquisition strategy and indicates the existence of a BNF-specific limiting phenomenon, not directly linked to micronutrient (Mo, Fe, Ni) concentration, by-products (hydrogen, hydrogen sulfide), or fundamental model metabolic parameters (death rate, electron acceptor stoichiometry). By providing quantitative predictions of environment and metabolism, this study contributes to a better understanding of anaerobic heterotrophic diazotrophs in environments with fluctuating N conditions.
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Affiliation(s)
- Romain Darnajoux
- Department of Geosciences, Princeton University, Princeton, NJ 08544, USA
- High Meadow Environmental Institute, Princeton University, Princeton, NJ 08544, USA
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA
| | - Xinning Zhang
- Department of Geosciences, Princeton University, Princeton, NJ 08544, USA
- High Meadow Environmental Institute, Princeton University, Princeton, NJ 08544, USA
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11
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Ortiz-Medina JF, Poole MR, Grunden AM, Call DF. Nitrogen Fixation and Ammonium Assimilation Pathway Expression of Geobacter sulfurreducens Changes in Response to the Anode Potential in Microbial Electrochemical Cells. Appl Environ Microbiol 2023; 89:e0207322. [PMID: 36975810 PMCID: PMC10132095 DOI: 10.1128/aem.02073-22] [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: 12/07/2022] [Accepted: 03/07/2023] [Indexed: 03/29/2023] Open
Abstract
Nitrogen gas (N2) fixation in the anode-respiring bacterium Geobacter sulfurreducens occurs through complex, multistep processes. Optimizing ammonium (NH4+) production from this bacterium in microbial electrochemical technologies (METs) requires an understanding of how those processes are regulated in response to electrical driving forces. In this study, we quantified gene expression levels (via RNA sequencing) of G. sulfurreducens growing on anodes fixed at two different potentials (-0.15 V and +0.15 V versus standard hydrogen electrode). The anode potential had a significant impact on the expression levels of N2 fixation genes. At -0.15 V, the expression of nitrogenase genes, such as nifH, nifD, and nifK, significantly increased relative to that at +0.15 V, as well as genes associated with NH4+ uptake and transformation, such as glutamine and glutamate synthetases. Metabolite analysis confirmed that both of these organic compounds were present in significantly higher intracellular concentrations at -0.15 V. N2 fixation rates (estimated using the acetylene reduction assay and normalized to total protein) were significantly larger at -0.15 V. Genes expressing flavin-based electron bifurcation complexes, such as electron-transferring flavoproteins (EtfAB) and the NADH-dependent ferredoxin:NADP reductase (NfnAB), were also significantly upregulated at -0.15 V, suggesting that these mechanisms may be involved in N2 fixation at that potential. Our results show that in energy-constrained situations (i.e., low anode potential), the cells increase per-cell respiration and N2 fixation rates. We hypothesize that at -0.15 V, they increase N2 fixation activity to help maintain redox homeostasis, and they leverage electron bifurcation as a strategy to optimize energy generation and use. IMPORTANCE Biological nitrogen fixation coupled with ammonium recovery provides a sustainable alternative to the carbon-, water-, and energy-intensive Haber-Bosch process. Aerobic biological nitrogen fixation technologies are hindered by oxygen gas inhibition of the nitrogenase enzyme. Electrically driving biological nitrogen fixation in anaerobic microbial electrochemical technologies overcomes this challenge. Using Geobacter sulfurreducens as a model exoelectrogenic diazotroph, we show that the anode potential in microbial electrochemical technologies has a significant impact on nitrogen gas fixation rates, ammonium assimilation pathways, and expression of genes associated with nitrogen gas fixation. These findings have important implications for understanding regulatory pathways of nitrogen gas fixation and will help identify target genes and operational strategies to enhance ammonium production in microbial electrochemical technologies.
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Affiliation(s)
- Juan F. Ortiz-Medina
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Mark R. Poole
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Amy M. Grunden
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA
| | - Douglas F. Call
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
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12
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Alam I, Zhang H, Du H, Rehman NU, Manghwar H, Lei X, Batool K, Ge L. Bioengineering Techniques to Improve Nitrogen Transformation and Utilization: Implications for Nitrogen Use Efficiency and Future Sustainable Crop Production. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:3921-3938. [PMID: 36842151 DOI: 10.1021/acs.jafc.2c08051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Nitrogen (N) is crucial for plant growth and development, especially in physiological and biochemical processes such as component of different proteins, enzymes, nucleic acids, and plant growth regulators. Six categories, such as transporters, nitrate absorption, signal molecules, amino acid biosynthesis, transcription factors, and miscellaneous genes, broadly encompass the genes regulating NUE in various cereal crops. Herein, we outline detailed research on bioengineering modifications of N metabolism to improve the different crop yields and biomass. We emphasize effective and precise molecular approaches and technologies, including N transporters, transgenics, omics, etc., which are opening up fascinating opportunities for a complete analysis of the molecular elements that contribute to NUE. Moreover, the detection of various types of N compounds and associated signaling pathways within plant organs have been discussed. Finally, we highlight the broader impacts of increasing NUE in crops, crucial for better agricultural yield and in the greater context of global climate change.
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Affiliation(s)
- Intikhab Alam
- College of Forestry and Landscape Architecture, Department of Grassland Science, South China Agricultural University (SCAU), Guangzhou 510642, China
- College of Life Sciences, SCAU, Guangzhou 510642, China
- Guangdong Subcenter of the National Center for Soybean Improvement, SCAU, Guangzhou 510642, China
| | - Hanyin Zhang
- College of Forestry and Landscape Architecture, Department of Grassland Science, South China Agricultural University (SCAU), Guangzhou 510642, China
- Guangdong Subcenter of the National Center for Soybean Improvement, SCAU, Guangzhou 510642, China
| | - Huan Du
- College of Forestry and Landscape Architecture, Department of Grassland Science, South China Agricultural University (SCAU), Guangzhou 510642, China
- College of Life Sciences, SCAU, Guangzhou 510642, China
- Guangdong Subcenter of the National Center for Soybean Improvement, SCAU, Guangzhou 510642, China
| | - Naveed Ur Rehman
- Guangdong Subcenter of the National Center for Soybean Improvement, SCAU, Guangzhou 510642, China
| | - Hakim Manghwar
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry and Landscape Architecture, SCAU, Guangzhou 510642, China
| | - Xiao Lei
- College of Forestry and Landscape Architecture, Department of Grassland Science, South China Agricultural University (SCAU), Guangzhou 510642, China
- Guangdong Subcenter of the National Center for Soybean Improvement, SCAU, Guangzhou 510642, China
| | - Khadija Batool
- College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Liangfa Ge
- College of Forestry and Landscape Architecture, Department of Grassland Science, South China Agricultural University (SCAU), Guangzhou 510642, China
- Guangdong Subcenter of the National Center for Soybean Improvement, SCAU, Guangzhou 510642, China
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13
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Sadler J, Brewster RC, Kjeldsen A, González AF, Nirkko JS, Varzandeh S, Wallace S. Overproduction of Native and Click-able Colanic Acid Slime from Engineered Escherichia coli. JACS AU 2023; 3:378-383. [PMID: 36873680 PMCID: PMC9976346 DOI: 10.1021/jacsau.2c00583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 01/27/2023] [Accepted: 01/27/2023] [Indexed: 06/18/2023]
Abstract
The fundamental biology and application of bacterial exopolysaccharides is gaining increasing attention. However, current synthetic biology efforts to produce the major component of Escherichia sp. slime, colanic acid, and functional derivatives thereof have been limited. Herein, we report the overproduction of colanic acid (up to 1.32 g/L) from d-glucose in an engineered strain of Escherichia coli JM109. Furthermore, we report that chemically synthesized l-fucose analogues containing an azide motif can be metabolically incorporated into the slime layer via a heterologous fucose salvage pathway from Bacteroides sp. and used in a click reaction to attach an organic cargo to the cell surface. This molecular-engineered biopolymer has potential as a new tool for use in chemical, biological, and materials research.
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Affiliation(s)
| | | | | | | | | | | | - Stephen Wallace
- Institute
of Quantitative Biology,
Biochemistry and Biotechnology, School of Biological Sciences, Roger
Land Building, Alexander Crum Brown Road, The King’s Buildings,
Edinburgh, EH9 3FF.
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14
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Kim J, Park M, Ahn E, Mao Q, Chen C, Ryu S, Jeon B. Stimulation of Surface Polysaccharide Production under Aerobic Conditions Confers Aerotolerance in Campylobacter jejuni. Microbiol Spectr 2023; 11:e0376122. [PMID: 36786626 PMCID: PMC10100837 DOI: 10.1128/spectrum.03761-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 01/30/2023] [Indexed: 02/15/2023] Open
Abstract
The ability of a foodborne pathogen to tolerate environmental stress critically affects food safety by increasing the risk of pathogen survival and transmission in the food supply chain. Campylobacter jejuni, a leading bacterial cause of foodborne illnesses, is an obligate microaerophile and is sensitive to atmospheric levels of oxygen. Currently, the molecular mechanisms of how C. jejuni withstands oxygen toxicity under aerobic conditions have not yet been fully elucidated. Here, we show that when exposed to aerobic conditions, C. jejuni develops a thick layer of bacterial capsules, which in turn protect C. jejuni under aerobic conditions. The presence of both capsular polysaccharides and lipooligosaccharides is required to protect C. jejuni from excess oxygen in oxygen-rich environments by alleviating oxidative stress. Under aerobic conditions, C. jejuni undergoes substantial transcriptomic changes, particularly in the genes of carbon metabolisms involved in amino acid uptake, the tricarboxylic acid (TCA) cycle, and the Embden-Meyerhof-Parnas (EMP) pathway despite the inability of C. jejuni to grow aerobically. Moreover, the stimulation of carbon metabolism by aerobiosis increases the level of glucose-6-phosphate, the EMP pathway intermediate required for the synthesis of surface polysaccharides. The disruption of the TCA cycle eliminates aerobiosis-mediated stimulation of surface polysaccharide production and markedly compromises aerotolerance in C. jejuni. These results in this study provide novel insights into how an oxygen-sensitive microaerophilic pathogen survives in oxygen-rich environments by adapting its metabolism and physiology. IMPORTANCE Oxygen-sensitive foodborne pathogens must withstand oxygen toxicity in aerobic environments during transmission to humans. C. jejuni is a major cause of gastroenteritis, accounting for 400 million to 500 million infection cases worldwide per year. As an obligate microaerophile, C. jejuni is sensitive to air-level oxygen. However, it has not been fully explained how this oxygen-sensitive zoonotic pathogen survives in aerobic environments and is transmitted to humans. Here, we show that under aerobic conditions, C. jejuni boosts its carbon metabolism to produce a thick layer of bacterial capsules, which in turn act as a protective barrier conferring aerotolerance. The new findings in this study improve our understanding of how oxygen-sensitive C. jejuni can survive in aerobic environments.
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Affiliation(s)
- Jinshil Kim
- Department of Food and Animal Biotechnology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea
- Center for Food and Bioconvergence, Seoul National University, Seoul, Republic of Korea
| | - Myungseo Park
- Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA
| | - Eunbyeol Ahn
- Department of Food and Animal Biotechnology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea
| | - Qingqing Mao
- Department of Food Science and Nutrition, University of Minnesota, Saint Paul, Minnesota, USA
| | - Chi Chen
- Department of Food Science and Nutrition, University of Minnesota, Saint Paul, Minnesota, USA
| | - Sangryeol Ryu
- Department of Food and Animal Biotechnology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea
- Center for Food and Bioconvergence, Seoul National University, Seoul, Republic of Korea
| | - Byeonghwa Jeon
- Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA
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15
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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: 8] [Impact Index Per Article: 8.0] [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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16
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Mutual supply of carbon and nitrogen sources in the co-culture of aerial microalgae and nitrogen-fixing bacteria. ALGAL RES 2023. [DOI: 10.1016/j.algal.2023.103001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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17
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Cydzik-Kwiatkowska A, Gusiatin MZ, Zielińska M, Wojnowska-Baryła I, Kulikowska D, Bernat K. Alginate-like polymers from full-scale aerobic granular sludge: content, recovery, characterization, and application for cadmium adsorption. Sci Rep 2022; 12:22260. [PMID: 36564508 PMCID: PMC9789099 DOI: 10.1038/s41598-022-26743-5] [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: 09/21/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022] Open
Abstract
Aerobic granular sludge (AGS) is a proven resource for the recovery of biopolymers like alginate-like polymers (ALP). This is the first report on the dynamics of ALP produced by AGS (ALP-AGS) in a full-scale wastewater treatment plant (WWTP), optimization of ALP recovery from AGS, and adsorption of cadmium (Cd2+) by ALP. Recovery of ALP was highest when using 120 mL of 0.2 M Na2CO3 at 70 °C for 45 min. Seasonal (1.5 years, over 3100 cycles) and intra-cycle changes in ALP-AGS in the WWTP were monitored. The ALP content in AGS increased in the transition period between winter and spring, reaching over 150 mg/g MLSS. In the batch reactor cycle, the ALP-AGS level peaked 2 h after the start of aeration (mean peak level: 120 mg/g MLSS), then decreased about two-fold by the end of the cycle. The ALP-AGS had a small surface area and a lamellar structure with crystalline outgrowths. The optimal conditions of Cd2+ adsorption with ALP were a dosage of 7.9 g d.m./L, a pH of 4-8, and an equilibrium time of 60 min. Carboxyl and hydroxyl groups were the key functional groups involved in Cd2+ adsorption. According to the Sips model, the maximum Cd2+ adsorption capacity of ALP-AGS was 29.5 mg/g d.m., which is similar to that of commercial alginate. AGS is a richer source of ALP than activated sludge, which ensures the cost-effectiveness of ALP recovery and increases the sustainability of wastewater treatment. Information on the chemical properties and yields of ALP from full-scale WWTPs is important for downstream applications with the recovered ALP.
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Affiliation(s)
- Agnieszka Cydzik-Kwiatkowska
- grid.412607.60000 0001 2149 6795Department of Environmental Biotechnology, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Słoneczna St. 45G, 10-709 Olsztyn, Poland
| | - Mariusz Z. Gusiatin
- grid.412607.60000 0001 2149 6795Department of Environmental Biotechnology, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Słoneczna St. 45G, 10-709 Olsztyn, Poland
| | - Magdalena Zielińska
- grid.412607.60000 0001 2149 6795Department of Environmental Biotechnology, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Słoneczna St. 45G, 10-709 Olsztyn, Poland
| | - Irena Wojnowska-Baryła
- grid.412607.60000 0001 2149 6795Department of Environmental Biotechnology, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Słoneczna St. 45G, 10-709 Olsztyn, Poland
| | - Dorota Kulikowska
- grid.412607.60000 0001 2149 6795Department of Environmental Biotechnology, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Słoneczna St. 45G, 10-709 Olsztyn, Poland
| | - Katarzyna Bernat
- grid.412607.60000 0001 2149 6795Department of Environmental Biotechnology, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Słoneczna St. 45G, 10-709 Olsztyn, Poland
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18
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Joublin-Delavat A, Touahri K, Crétin P, Morot A, Rodrigues S, Jesus B, Trigodet F, Delavat F. Genetic and physiological insights into the diazotrophic activity of a non-cyanobacterial marine diazotroph. Environ Microbiol 2022; 24:6510-6523. [PMID: 36302093 PMCID: PMC10099842 DOI: 10.1111/1462-2920.16261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 10/21/2022] [Indexed: 01/12/2023]
Abstract
Nitrogen (N2 ) fixation, or diazotrophy, supports a large part of primary production in oceans. Culture-independent approaches highlighted the presence in abundance of marine non-cyanobacterial diazotrophs (NCD), but their ecophysiology remains elusive, mostly because of the low number of isolated NCD and because of the lack of available genetic tools for these isolates. Here, a dual genetic and functional approach allowed unveiling the ecophysiology of a marine NCD affiliated to the species Vibrio diazotrophicus. Physiological characterization of the first marine NCD mutant obtained so far was performed using a soft-gellan assay, demonstrating that a ΔnifH mutant is not able to grow in nitrogen-free media. Furthermore, we demonstrated that V. diazotrophicus produces a thick biofilm under diazotrophic conditions, suggesting biofilm production as an adaptive response of this NCD to cope with the inhibition of nitrogen fixation by molecular oxygen. Finally, the genomic signature of V. diazotrophicus is essentially absent from metagenomic data of Tara Ocean expeditions, despite having been isolated from various marine environments. We think that the genetically tractable V. diazotrophicus strain used in this study may serve as an ideal model to study the ecophysiology of these overlooked procaryotic group.
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Affiliation(s)
| | - Katia Touahri
- Nantes Université, CNRS, US2B, UMR6286, Nantes, France.,Laboratoire Chimie et Biochimie de Molécules Bioactives, Université de Strasbourg/CNRS, UMR7177, Strasbourg, France
| | | | - Amandine Morot
- Univ Brest, CNRS, IRD, Ifremer, LEMAR, Plouzané, France.,Université de Bretagne-Sud, UR3884, LBCM, IUEM, Lorient, France
| | | | - Bruno Jesus
- Nantes Université, RSBE2 ISOMer, UR2160, Nantes, France
| | - Florian Trigodet
- Department of Medicine, The University of Chicago, Chicago, Illinois, USA
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19
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Rnf and Fix Have Specific Roles during Aerobic Nitrogen Fixation in Azotobacter vinelandii. Appl Environ Microbiol 2022; 88:e0104922. [PMID: 36000884 PMCID: PMC9469703 DOI: 10.1128/aem.01049-22] [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: 11/20/2022] Open
Abstract
Biological nitrogen fixation requires large amounts of energy in the form of ATP and low potential electrons to overcome the high activation barrier for cleavage of the dinitrogen triple bond. The model aerobic nitrogen-fixing bacteria, Azotobacter vinelandii, generates low potential electrons in the form of reduced ferredoxin (Fd) and flavodoxin (Fld) using two distinct mechanisms via the enzyme complexes Rnf and Fix. Both Rnf and Fix are expressed during nitrogen fixation, but deleting either rnf1 or fix genes has little effect on diazotrophic growth. However, deleting both rnf1 and fix eliminates the ability to grow diazotrophically. Rnf and Fix both use NADH as a source of electrons, but overcoming the energetics of NADH's endergonic reduction of Fd/Fld is accomplished through different mechanisms. Rnf harnesses free energy from the chemiosmotic potential, whereas Fix uses electron bifurcation to effectively couple the endergonic reduction of Fd/Fld to the exergonic reduction of quinone. Different reaction stoichiometries and condition-specific differential gene expression indicate specific roles for the two reactions. This work's complementary physiological studies and thermodynamic modeling reveal how Rnf and Fix balance redox homeostasis in various conditions. Specifically, the Fix complex is required for efficient growth under low oxygen concentrations, while Rnf is presumed to maintain reduced Fd/Fld production for nitrogenase under standard conditions. This work provides a framework for understanding how the production of low potential electrons sustains robust nitrogen fixation in various conditions. IMPORTANCE The availability of fixed nitrogen is critical for life in many ecosystems, from extreme environments to agriculture. Due to the energy demands of biological nitrogen fixation, organisms must tailor their metabolism during diazotrophic growth to deliver the energy requirements to nitrogenase in the form of ATP and low potential electrons. Therefore, a complete understanding of diazotrophic energy metabolism and redox homeostasis is required to understand the impact on ecological communities or to promote crop growth in agriculture through engineered diazotrophs.
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20
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Wakarera PW, Ojola P, Njeru EM. Characterization and diversity of native Azotobacter spp. isolated from semi-arid agroecosystems of Eastern Kenya. Biol Lett 2022; 18:20210612. [PMID: 35317624 PMCID: PMC8941396 DOI: 10.1098/rsbl.2021.0612] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Declining food production in African agroecosystems is attributable to changes in weather patterns, soil infertility and limited farming inputs. The exploitation of plant growth-promoting soil microbes could remedy these problems. Such microbes include Azotobacter; free-living, nitrogen-fixing bacteria, which confer stress tolerance, avail phytohormones and aid in soil bioremediation. Here, we aimed to isolate, characterize and determine the biodiversity of native Azotobacter isolates from soils in semi-arid Eastern Kenya. Isolation was conducted on nitrogen-free Ashby's agar and the morphological, biochemical and molecular attributes evaluated. The isolates were sequenced using DNA amplicons of 27F and 1492R primers of the 16S rRNA gene loci. The Basic Local Alignment Search Tool (BLASTn) analysis of their sequences revealed the presence of three main Azotobacter species viz., Azotobacter vinelandii, Azotobacter salinestris and Azotobacter tropicalis. Kitui County recorded the highest number of recovered Azotobacter isolates (45.4%) and lowest diversity index (0.8761). Tharaka Nithi County showed the lowest occurrence (26.36%) with a diversity index of (1.057). The diversity was influenced by the soil pH, texture and total organic content. This study reports for the first time a wide diversity of Azotobacter species from a semi-arid agroecosystem in Kenya with potential for utilization as low-cost, free-living nitrogen-fixing bioinoculant.
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Affiliation(s)
- Priscillah Wanjira Wakarera
- Department of Biochemistry, Microbiology and Biotechnology, Kenyatta University, PO Box 43844-00100, Nairobi, Kenya
| | - Patroba Ojola
- Department of Biochemistry, Microbiology and Biotechnology, Kenyatta University, PO Box 43844-00100, Nairobi, Kenya
| | - Ezekiel Mugendi Njeru
- Department of Biochemistry, Microbiology and Biotechnology, Kenyatta University, PO Box 43844-00100, Nairobi, Kenya
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21
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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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22
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Qian L, Ye X, Xiao J, Lin S, Wang H, Liu Z, Ma Y, Yang L, Zhang Z, Wu L. Nitrogen concentration acting as an environmental signal regulates cyanobacterial EPS excretion. CHEMOSPHERE 2022; 291:132878. [PMID: 34780741 DOI: 10.1016/j.chemosphere.2021.132878] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 10/15/2021] [Accepted: 11/09/2021] [Indexed: 06/13/2023]
Abstract
As an important carbon (C) storage in biological soil crusts (BSCs), exopolysaccharides (EPSs) are not only a part of the desert C cycle, but also the key materials for cyanobacteria to resist desert stress. In this study, the influence of initial N concentrations (10, 25 and 50 mg L-1 designated as N10, N25 and N50 respectively) on Microcoleus vaginatusis growth and the excretion of EPSs including RPS (released exopolysaccharides) and CPS (capsule exopolysaccharides) were evaluated at different growth periods. In logarithmic period, higher ratio of biomass to EPSs indicated by (DW-CPS)/EPSs was observed in the N50 group with the highest N concentration (about 40 mg L-1) in the medium, while no difference was observed among the three groups in stationary period when the N concentrations of medium were lower than 25 mg L-1. The CPS/RPS showed similar results with (DW-CPS)/EPSs, and stayed higher than 1 in each group. Notably, obvious difference displayed in the monosaccharidic composition and morphologies between CPS and RPS, but not the N levels. The changes of C/N in cells at different growth period indicate that the excretion of EPSs, a mechanism that maintains the balance of cell C/N ratio, only works when the N in the environment is sufficient. Our results showed that, as the raw material and environmental signal, environmental N concentration regulates the elements (C and N) percentage of cyanobacterial cells and its EPSs excretion pattern, but not the monosaccharidic composition or the morphologies. These results also implied that, as the essential self-protecting materials, more EPSs with higher proportion of CPS would be excreted to response the low N environment.
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Affiliation(s)
- Long Qian
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China
| | - Xingwang Ye
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China
| | - Jingshang Xiao
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China
| | - Simeng Lin
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China
| | - Hongyu Wang
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China
| | - Zhe Liu
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China
| | - Yongfei Ma
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China
| | - Lie Yang
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China
| | - Zulin Zhang
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China; The James Hutton Institute, Craigiebuckler, Aberdeen, ABI5 8QH, UK
| | - Li Wu
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430072, China.
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Dudun AA, Akoulina EA, Zhuikov VA, Makhina TK, Voinova VV, Belishev NV, Khaydapova DD, Shaitan KV, Bonartseva GA, Bonartsev AP. Competitive Biosynthesis of Bacterial Alginate Using Azotobacter vinelandii 12 for Tissue Engineering Applications. Polymers (Basel) 2021; 14:polym14010131. [PMID: 35012152 PMCID: PMC8747204 DOI: 10.3390/polym14010131] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/17/2021] [Accepted: 12/23/2021] [Indexed: 11/16/2022] Open
Abstract
This study investigated the effect of various cultivation conditions (sucrose/phosphate concentrations, aeration level) on alginate biosynthesis using the bacterial producing strain Azotobacter vinelandii 12 by the full factorial design (FFD) method and physicochemical properties (e.g., rheological properties) of the produced bacterial alginate. We demonstrated experimentally the applicability of bacterial alginate for tissue engineering (the cytotoxicity testing using mesenchymal stem cells (MSCs)). The isolated synthesis of high molecular weight (Mw) capsular alginate with a high level of acetylation (25%) was achieved by FFD method under a low sucrose concentration, an increased phosphate concentration, and a high aeration level. Testing the viscoelastic properties and cytotoxicity showed that bacterial alginate with a maximal Mw (574 kDa) formed the densest hydrogels (which demonstrated relatively low cytotoxicity for MSCs in contrast to bacterial alginate with low Mw). The obtained data have shown promising prospects in controlled biosynthesis of bacterial alginate with different physicochemical characteristics for various biomedical applications including tissue engineering.
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Affiliation(s)
- Andrei A. Dudun
- Research Center of Biotechnology of the Russian Academy of Sciences Leninsky Ave, 33, Bld. 2, 119071 Moscow, Russia; (A.A.D.); (V.A.Z.); (T.K.M.); (G.A.B.)
| | - Elizaveta A. Akoulina
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory 1-12, 119234 Moscow, Russia; (E.A.A.); (V.V.V.); (N.V.B.); (K.V.S.)
| | - Vsevolod A. Zhuikov
- Research Center of Biotechnology of the Russian Academy of Sciences Leninsky Ave, 33, Bld. 2, 119071 Moscow, Russia; (A.A.D.); (V.A.Z.); (T.K.M.); (G.A.B.)
| | - Tatiana K. Makhina
- Research Center of Biotechnology of the Russian Academy of Sciences Leninsky Ave, 33, Bld. 2, 119071 Moscow, Russia; (A.A.D.); (V.A.Z.); (T.K.M.); (G.A.B.)
| | - Vera V. Voinova
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory 1-12, 119234 Moscow, Russia; (E.A.A.); (V.V.V.); (N.V.B.); (K.V.S.)
| | - Nikita V. Belishev
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory 1-12, 119234 Moscow, Russia; (E.A.A.); (V.V.V.); (N.V.B.); (K.V.S.)
| | - Dolgor D. Khaydapova
- Department of Soil Physics and Reclamation, Soil Science Faculty, M.V. Lomonosov Moscow State University, Leninskie Gory 1-12, 119234 Moscow, Russia;
| | - Konstantin V. Shaitan
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory 1-12, 119234 Moscow, Russia; (E.A.A.); (V.V.V.); (N.V.B.); (K.V.S.)
| | - Garina A. Bonartseva
- Research Center of Biotechnology of the Russian Academy of Sciences Leninsky Ave, 33, Bld. 2, 119071 Moscow, Russia; (A.A.D.); (V.A.Z.); (T.K.M.); (G.A.B.)
| | - Anton P. Bonartsev
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory 1-12, 119234 Moscow, Russia; (E.A.A.); (V.V.V.); (N.V.B.); (K.V.S.)
- Correspondence: ; Tel.: +7-4959306306
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Metabolic Model of the Nitrogen-Fixing Obligate Aerobe Azotobacter vinelandii Predicts Its Adaptation to Oxygen Concentration and Metal Availability. mBio 2021; 12:e0259321. [PMID: 34903060 PMCID: PMC8686835 DOI: 10.1128/mbio.02593-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
There is considerable interest in promoting biological nitrogen fixation (BNF) as a mechanism to reduce the inputs of nitrogenous fertilizers in agriculture, but considerable fundamental knowledge gaps still need to be addressed. BNF is catalyzed by nitrogenase, which requires a large input of energy in the form of ATP and low potential electrons. Diazotrophs that respire aerobically have an advantage in meeting the ATP demands of BNF but face challenges in protecting nitrogenase from inactivation by oxygen. Here, we constructed a genome-scale metabolic model of the nitrogen-fixing bacterium Azotobacter vinelandii, which uses a complex respiratory protection mechanism to consume oxygen at a high rate to keep intracellular conditions microaerobic. Our model accurately predicts growth rate under high oxygen and substrate concentrations, consistent with a large electron flux directed to the respiratory protection mechanism. While a partially decoupled electron transport chain compensates for some of the energy imbalance under high-oxygen conditions, it does not account for all substrate intake, leading to increased maintenance rates. Interestingly, the respiratory protection mechanism is required for accurate predictions even when ammonia is supplemented during growth, suggesting that the respiratory protection mechanism might be a core principle of metabolism and not just used for nitrogenase protection. We have also shown that rearrangement of flux through the electron transport system allows A. vinelandii to adapt to different oxygen concentrations, metal availability, and genetic disruption, which cause an ammonia excretion phenotype. Accurately determining the energy balance in an aerobic nitrogen-fixing metabolic model is required for future engineering approaches.
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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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Tyrosine Kinase Self-Phosphorylation Controls Exopolysaccharide Biosynthesis in Gluconacetobacter diazotrophicus Strain Pal5. Life (Basel) 2021; 11:life11111231. [PMID: 34833106 PMCID: PMC8620434 DOI: 10.3390/life11111231] [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: 08/23/2021] [Revised: 10/28/2021] [Accepted: 11/10/2021] [Indexed: 11/16/2022] Open
Abstract
The biosynthesis of exopolysaccharides (EPSs) is essential for endophytic bacterial colonisation in plants bacause this exopolymer both protects bacterial cells against the defence and oxidative systems of plants and acts on the plant colonisation mechanism in Gluconacetobacter diazotrophicus. The pathway involved in the biosynthesis of bacterial EPS has not been fully elucidated, and several areas related to its molecular regulation mechanisms are still lacking. G. diazotrophicus relies heavily on EPS for survival indirectly by protecting plants from pathogen attack as well as for endophytic maintenance and adhesion in plant tissues. Here, we report that EPS from G. diazotrophicus strain Pal5 is a signal polymer that controls its own biosynthesis. EPS production depends on a bacterial tyrosine (BY) kinase (Wzc) that consists of a component that is able to phosphorylate a glycosyltranferase or to self-phosphorylate. EPS interacts with the extracellular domain of Wzc, which regulates kinase activity. In G. diazotrophicus strains that are deficient in EPS production, the Wzc is rendered inoperative by self-phosphorylation. The presence of EPS promotes the phosphorylation of a glycosyltransferase in the pathway, thus producing EPS. Wzc-mediated self-regulation is an attribute for the control of exopolysaccharide biosynthesis in G. diazotrophicus.
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Tatemichi Y, Nakahara T, Ueda M, Kuroda K. Construction of recombinant Escherichia coli producing nitrogenase-related proteins from Azotobacter vinelandii. Biosci Biotechnol Biochem 2021; 85:2209-2216. [PMID: 34387317 DOI: 10.1093/bbb/zbab144] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 08/05/2021] [Indexed: 11/12/2022]
Abstract
Biological nitrogen fixation by nitrogenase has attracted attention as an alternative method to chemical nitrogen fixation, which requires large amounts of fossil fuels. Azotobacter vinelandii, which produces an oxygen-sensitive nitrogenase, can fix nitrogen even under aerobic conditions; therefore, the heterologous expression of nif-related genes from A. vinelandii is a promising strategy for developing a biological nitrogen fixation method. We assembled 17 nif-related genes, which are scattered throughout the genome of A. vinelandii, into synthetic gene clusters by overlap-extension-PCR and seamless cloning and expressed them in Escherichia coli. The transcription and translation of the 17 nif-related genes were evaluated by RT-qPCR and LC-MS/MS, respectively. The constructed E. coli showed nitrogenase activity under anaerobic and microaerobic conditions. This strain would be a useful model for examining the effect of other genes from A. vinelandii on nitrogen fixation by expressing them in addition to the minimal set of nif-related genes.
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Affiliation(s)
- Yuki Tatemichi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-Ku, Kyoto, Japan
- Research and Development Division, Kikkoman Corporation, Noda-City, Chiba, Japan
| | - Takeharu Nakahara
- Research and Development Division, Kikkoman Corporation, Noda-City, Chiba, Japan
| | - Mitsuyoshi Ueda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-Ku, Kyoto, Japan
| | - Kouichi Kuroda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-Ku, Kyoto, Japan
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28
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Simunović V. Genomic and molecular evidence reveals novel pathways associated with cell surface polysaccharides in bacteria. FEMS Microbiol Ecol 2021; 97:6355432. [PMID: 34415013 DOI: 10.1093/femsec/fiab119] [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: 05/21/2021] [Accepted: 08/18/2021] [Indexed: 11/13/2022] Open
Abstract
Amino acid (acyl carrier protein) ligases (AALs) are a relatively new family of bacterial amino acid adenylating enzymes with unknown function(s). Here, genomic enzymology tools that employ sequence similarity networks and genome context analyses were used to hypothesize the metabolic function(s) of AALs. In over 50% of species, aal and its cognate acyl carrier protein (acp) genes, along with three more genes, formed a highly conserved AAL cassette. AAL cassettes were strongly associated with surface polysaccharide gene clusters in Proteobacteria and Actinobacteria, yet were prevalent among soil and rhizosphere-associated α- and β-Proteobacteria, including symbiotic α- and β-rhizobia and some Mycolata. Based on these associations, AAL cassettes were proposed to encode a noncanonical Acp-dependent polysaccharide modification route. Genomic-inferred predictions were substantiated by published experimental evidence, revealing a role for AAL cassettes in biosynthesis of biofilm-forming exopolysaccharide in pathogenic Burkholderia and expression of aal and acp genes in nitrogen-fixing Rhizobium bacteroids. Aal and acp genes were associated with dltBD-like homologs that modify cell wall teichoic acids with d-alanine, including in Paenibacillus and certain other bacteria. Characterization of pathways that involve AAL and Acp may lead to developing new plant and human disease-controlling agents as well as strains with improved nitrogen fixation capacity.
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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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30
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Borisov VB, Siletsky SA, Paiardini A, Hoogewijs D, Forte E, Giuffrè A, Poole RK. Bacterial Oxidases of the Cytochrome bd Family: Redox Enzymes of Unique Structure, Function, and Utility As Drug Targets. Antioxid Redox Signal 2021; 34:1280-1318. [PMID: 32924537 PMCID: PMC8112716 DOI: 10.1089/ars.2020.8039] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 09/01/2020] [Accepted: 09/02/2020] [Indexed: 12/23/2022]
Abstract
Significance: Cytochrome bd is a ubiquinol:oxygen oxidoreductase of many prokaryotic respiratory chains with a unique structure and functional characteristics. Its primary role is to couple the reduction of molecular oxygen, even at submicromolar concentrations, to water with the generation of a proton motive force used for adenosine triphosphate production. Cytochrome bd is found in many bacterial pathogens and, surprisingly, in bacteria formally denoted as anaerobes. It endows bacteria with resistance to various stressors and is a potential drug target. Recent Advances: We summarize recent advances in the biochemistry, structure, and physiological functions of cytochrome bd in the light of exciting new three-dimensional structures of the oxidase. The newly discovered roles of cytochrome bd in contributing to bacterial protection against hydrogen peroxide, nitric oxide, peroxynitrite, and hydrogen sulfide are assessed. Critical Issues: Fundamental questions remain regarding the precise delineation of electron flow within this multihaem oxidase and how the extraordinarily high affinity for oxygen is accomplished, while endowing bacteria with resistance to other small ligands. Future Directions: It is clear that cytochrome bd is unique in its ability to confer resistance to toxic small molecules, a property that is significant for understanding the propensity of pathogens to possess this oxidase. Since cytochrome bd is a uniquely bacterial enzyme, future research should focus on harnessing fundamental knowledge of its structure and function to the development of novel and effective antibacterial agents.
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Affiliation(s)
- Vitaliy B. Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Sergey A. Siletsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | | | - David Hoogewijs
- Department of Medicine/Physiology, University of Fribourg, Fribourg, Switzerland
| | - Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, Rome, Italy
| | | | - Robert K. Poole
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
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Imran A, Hakim S, Tariq M, Nawaz MS, Laraib I, Gulzar U, Hanif MK, Siddique MJ, Hayat M, Fraz A, Ahmad M. Diazotrophs for Lowering Nitrogen Pollution Crises: Looking Deep Into the Roots. Front Microbiol 2021; 12:637815. [PMID: 34108945 PMCID: PMC8180554 DOI: 10.3389/fmicb.2021.637815] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 03/24/2021] [Indexed: 12/14/2022] Open
Abstract
During and after the green revolution in the last century, agrochemicals especially nitrogen (N) were extensively used. However, it resulted in a remarkable increase in crop yield but drastically reduced soil fertility; increased the production cost, food prices, and carbon footprints; and depleted the fossil reserves with huge penalties to the environment and ecological sustainability. The groundwater, rivers, and oceans are loaded with N excess which is an environmental catastrophe. Nitrogen emissions (e.g., ammonia, nitrogen oxide, nitrous oxide) play an important role in global climate change and contribute to particulate matter and acid rain causing respiratory problems, cancers, and damage to forests and buildings. Therefore, the nitrogen-polluted planet Earth needs concerted global efforts to avoid the disaster. Improved agricultural N management focuses on the synchronization of crop N demand and N supply along with improving the N-use efficiency of the crops. However, there is very little focus on the natural sources of N available for plants in the form of diazotrophic bacteria present inside or on the root surface and the rhizosphere. These diazotrophs are the mini-nitrogen factories that convert available (78%) atmospheric N2 to ammonia through a process known as "biological nitrogen fixation" which is then taken up by the plants for its metabolic functioning. Diazotrophs also stimulate root architecture by producing plant hormones and hence improve the plant's overall ability to uptake nutrients and water. In recent years, nanotechnology has revolutionized the whole agri-industry by introducing nano-fertilizers and coated/slow-releasing fertilizers. With this in mind, we tried to explore the following questions: To what extent can the crop N requirements be met by diazotroph inoculation? Can N input to agriculture be managed in a way leading to environmental benefits and farmers saving money? Can nanotechnology help in technological advancement of diazotroph application? The review suggests that an integrated technology based on slow-releasing nano-fertilizer combined with diazotrophs should be adopted to decrease nitrogen inputs to the agricultural system. This integrated technology would minimize N pollution and N losses to much extent.
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Affiliation(s)
- Asma Imran
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
| | - Sughra Hakim
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
| | - Mohsin Tariq
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
- Department of Bioinformatics and Biotechnology, Government College University, Faisalabad, Pakistan
- Department of Botany, Government College University, Faisalabad, Pakistan
| | - Muhammad Shoib Nawaz
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
| | - Iqra Laraib
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
| | - Umaira Gulzar
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
- Department of Botany, University of Bagh, Kotli, Pakistan
| | - Muhammad Kashif Hanif
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
- Department of Biotechnology, Institute of Molecular Biology and Biotechnology, University of Lahore, Sargodha, Pakistan
| | - Muhammad Jawad Siddique
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
| | - Mahnoor Hayat
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
| | - Ahmad Fraz
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
- Department of Bioinformatics and Biotechnology, Government College University, Faisalabad, Pakistan
- Department of Botany, Government College University, Faisalabad, Pakistan
| | - Muhammad Ahmad
- Division of Soil and Environmental Biotechnology, National Institute for Biotechnology and Genetic Engineering-Campus-Pakistan Institute of Engineering and Applied Sciences (NIBGE-C-PIEAS), Faisalabad, Pakistan
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Hövels M, Kosciow K, Deppenmeier U. Characterization of a novel endo-levanase from Azotobacter chroococcum DSM 2286 and its application for the production of prebiotic fructooligosaccharides. Carbohydr Polym 2021; 255:117384. [DOI: 10.1016/j.carbpol.2020.117384] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 11/03/2020] [Accepted: 11/04/2020] [Indexed: 10/23/2022]
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Kim J, Hiltpold I, Jaffuel G, Sbaiti I, Hibbard BE, Turlings TCJ. Calcium-alginate beads as a formulation for the application of entomopathogenic nematodes to control rootworms. JOURNAL OF PEST SCIENCE 2021; 94:1197-1208. [PMID: 34720786 PMCID: PMC8550308 DOI: 10.1007/s10340-021-01349-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 01/29/2021] [Accepted: 02/06/2021] [Indexed: 06/13/2023]
Abstract
Entomopathogenic nematodes (EPN) have great potential as biological control agents against root-feeding insects. They have a rapid and long-lasting mode of action, minimal adverse effects on the environment and can be readily mass-produced. However, they have a relatively short shelf-life and are susceptible to desiccation and UV light. These shortcomings may be overcome by encapsulating EPN in Ca2+-alginate hydrogels, which have been shown to provide a humid and UV protective shelter. Yet, current Ca2+-alginate formulations do not keep EPN vigorous and infectious for a prolonged period of time and do not allow for their controlled release upon application. Here, we introduce solid Ca2+-alginate beads which we supplemented with glycerol to better retain the EPN during storage and to ensure a steady release when applied in soil. Glycerol-induced metabolic arrest in EPN (Heterorhabditis bacteriophora) resulting in quiescence and total retainment of EPN when added to beads made with 0.5% sodium alginate and 2% CaCl2·2H2O solutions. More than 4,000 EPN could be embedded in a single 4-5-mm diameter bead, and quiescence could be broken by adding water, after which the EPN readily emerged from the beads. In a field trial, the EPN beads were as effective in reducing root damage by the western corn rootworm (WCR, Diabrotica virgifera virgifera) as EPN that were applied in water. Although further improvements are desirable, we conclude that Ca2+-alginate beads can provide an effective and practical way to apply EPN for the control of WCR larvae. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s10340-021-01349-4.
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Affiliation(s)
- Jinwon Kim
- FARCE Laboratory, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
- Seoul Viosys Co. Ltd., Ansan, Gyeonggi-do Republic of Korea
| | - Ivan Hiltpold
- Division of Plant Sciences, University of Missouri, Columbia, MO USA
- Agroscope, Route de Duillier 50, P.O. Box 1012, 1260 Nyon 1, Switzerland
| | - Geoffrey Jaffuel
- FARCE Laboratory, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Ilham Sbaiti
- FARCE Laboratory, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Bruce E. Hibbard
- Division of Plant Sciences, University of Missouri, Columbia, MO USA
- USDA-ARS, Plant Genetics Research Unit, University of Missouri, Columbia, MO USA
| | - Ted C. J. Turlings
- FARCE Laboratory, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
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34
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Díaz-Barrera A, Sanchez-Rosales F, Padilla-Córdova C, Andler R, Peña C. Molecular weight and guluronic/mannuronic ratio of alginate produced by Azotobacter vinelandii at two bioreactor scales under diazotrophic conditions. Bioprocess Biosyst Eng 2021; 44:1275-1287. [PMID: 33635396 DOI: 10.1007/s00449-021-02532-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 02/07/2021] [Indexed: 11/24/2022]
Abstract
Alginates can be used to elaborate hydrogels, and their properties depend on the molecular weight (MW) and the guluronic (G) and mannuronic (M) composition. In this study, the MW and G/M ratio were evaluated in cultures of Azotobacter vinelandii to 3 and 30 L scales at different oxygen transfer rates (OTRs) under diazotrophic conditions. An increase in the maximum OTR (OTRmax) improved the alginate production, reaching 3.3 ± 0.2 g L-1. In the cultures conducted to an OTR of 10.4 mmol L-1 h-1 (500 rpm), the G/M increased during the cell growth phase and decreased during the stationary phase; whereas, in the cultures at 19.2 mmol L-1 h-1 was constant throughout the cultivation. A higher alginate MW (520 ± 43 kDa) and G/M ratio (0.86 ± 0.01) were obtained in the cultures conducted at 10.4 mmol L-1 h-1. The OTR as a criterion to scale up alginate production allowed to replicate the concentration and the alginate production rate; however, it was not possible reproduce the MW and G/M ratio. Under a similar specific oxygen uptake rate (qO2) (approximately 65 mmol g-1 h-1) the alginate MW was similar (approximately 365 kDa) in both scales. The evidences revealed that the qO2 can be a parameter adequate to produce alginate MW similar in two bioreactor scales. Overall, the results have shown that the alginate composition could be affected by cellular respiration, and from a technological perspective the evidences contribute to the design process based on oxygen consumption to produce alginates defined.
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Affiliation(s)
- Alvaro Díaz-Barrera
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147, 4059, Casilla, Valparaíso, Chile.
| | - Francisco Sanchez-Rosales
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147, 4059, Casilla, Valparaíso, Chile.,Facultad de Ciencias Tecnológicas, Universidad Nacional de Agricultura, Carretera a Dulce Nombre de Culmí, km 212, Barrio El Espino, Catacamas, Honduras
| | - Claudio Padilla-Córdova
- Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2147, 4059, Casilla, Valparaíso, Chile
| | - Rodrigo Andler
- Escuela de Ingeniería en Biotecnología, Universidad Católica del Maule, Talca, Chile
| | - Carlos Peña
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
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Effects of an EPS Biosynthesis Gene Cluster of Paenibacillus polymyxa WLY78 on Biofilm Formation and Nitrogen Fixation under Aerobic Conditions. Microorganisms 2021; 9:microorganisms9020289. [PMID: 33573330 PMCID: PMC7911366 DOI: 10.3390/microorganisms9020289] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 01/26/2021] [Accepted: 01/27/2021] [Indexed: 11/17/2022] Open
Abstract
Exopolysaccharides (EPS) are of high significance in bacterial biofilm formation. However, the effects of EPS cluster(s) on biofilm formation in Paenibacillus species are little known. In this study, we have shown that Paenibacillus polymyxa WLY78, a N2-fixing bacterium, can form biofilm. EPS is the major component of the extracellular matrix. The genome of P. polymyxa WLY78 contains two putative gene clusters (designated pep-1 cluster and pep-2 cluster). The pep-1 cluster is composed of 12 putative genes (pepO-lytR) co-located in a 13 kb region. The pep-2 cluster contains 17 putative genes (pepA-pepN) organized as an operon in a 20 kb region. Mutation analysis reveals that the pep-2 cluster is involved in EPS biosynthesis and biofilm formation. Disruption of the pep-2 cluster also leads to the enhancement of motility and change of the colony morphology. In contrast, disruption of the pep-1 cluster does not affect EPS synthesis or biofilm formation. More importantly, the biofilm allowed P. polymyxa WLY78 to fix nitrogen in aerobic conditions, suggesting that biofilm may provide a microaerobic environment for nitrogenase synthesis and activity.
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Desiccation-tolerant fungal blastospores: From production to application. CURRENT RESEARCH IN BIOTECHNOLOGY 2021. [DOI: 10.1016/j.crbiot.2021.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Inomura K, Deutsch C, Masuda T, Prášil O, Follows MJ. Quantitative models of nitrogen-fixing organisms. Comput Struct Biotechnol J 2020; 18:3905-3924. [PMID: 33335688 PMCID: PMC7733014 DOI: 10.1016/j.csbj.2020.11.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 11/11/2020] [Accepted: 11/13/2020] [Indexed: 10/26/2022] Open
Abstract
Nitrogen-fixing organisms are of importance to the environment, providing bioavailable nitrogen to the biosphere. Quantitative models have been used to complement the laboratory experiments and in situ measurements, where such evaluations are difficult or costly. Here, we review the current state of the quantitative modeling of nitrogen-fixing organisms and ways to enhance the bridge between theoretical and empirical studies.
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Affiliation(s)
- Keisuke Inomura
- School of Oceanography, University of Washington, Seattle, WA, USA
| | - Curtis Deutsch
- School of Oceanography, University of Washington, Seattle, WA, USA
| | - Takako Masuda
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, Třeboň, Czech Republic
| | - Ondřej Prášil
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, Třeboň, Czech Republic
| | - Michael J. Follows
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
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38
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Respiration in Azotobacter vinelandii and its relationship with the synthesis of biopolymers. ELECTRON J BIOTECHN 2020. [DOI: 10.1016/j.ejbt.2020.08.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Soumare A, Diedhiou AG, Thuita M, Hafidi M, Ouhdouch Y, Gopalakrishnan S, Kouisni L. Exploiting Biological Nitrogen Fixation: A Route Towards a Sustainable Agriculture. PLANTS 2020; 9:plants9081011. [PMID: 32796519 PMCID: PMC7464700 DOI: 10.3390/plants9081011] [Citation(s) in RCA: 85] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 07/08/2020] [Accepted: 07/10/2020] [Indexed: 12/13/2022]
Abstract
For all living organisms, nitrogen is an essential element, while being the most limiting in ecosystems and for crop production. Despite the significant contribution of synthetic fertilizers, nitrogen requirements for food production increase from year to year, while the overuse of agrochemicals compromise soil health and agricultural sustainability. One alternative to overcome this problem is biological nitrogen fixation (BNF). Indeed, more than 60% of the fixed N on Earth results from BNF. Therefore, optimizing BNF in agriculture is more and more urgent to help meet the demand of the food production needs for the growing world population. This optimization will require a good knowledge of the diversity of nitrogen-fixing microorganisms, the mechanisms of fixation, and the selection and formulation of efficient N-fixing microorganisms as biofertilizers. Good understanding of BNF process may allow the transfer of this ability to other non-fixing microorganisms or to non-leguminous plants with high added value. This minireview covers a brief history on BNF, cycle and mechanisms of nitrogen fixation, biofertilizers market value, and use of biofertilizers in agriculture. The minireview focuses particularly on some of the most effective microbial products marketed to date, their efficiency, and success-limiting in agriculture. It also highlights opportunities and difficulties of transferring nitrogen fixation capacity in cereals.
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Affiliation(s)
- Abdoulaye Soumare
- AgroBioSciences Program, Mohammed VI Polytechnic University (UM6P), Benguerir 43150, Morocco; (M.H.); (Y.O.); (L.K.)
- Laboratoire Commun de Microbiologie (LCM) IRD/ISRA/UCAD, Centre de Recherche de Bel Air, Dakar 1386, Senegal
- Correspondence: (A.S.); (A.G.D.)
| | - Abdala G. Diedhiou
- Laboratoire Commun de Microbiologie (LCM) IRD/ISRA/UCAD, Centre de Recherche de Bel Air, Dakar 1386, Senegal
- Département de Biologie Végétale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop (UCAD) de Dakar, Dakar 1386, Senegal
- Centre d’Excellence Africain en Agriculture pour la Sécurité Alimentaire et Nutritionnelle (CEA-AGRISAN), UCAD, Dakar 18524, Senegal
- Correspondence: (A.S.); (A.G.D.)
| | - Moses Thuita
- International Institute of Tropical Agriculture, Nairobi PO BOX 30772-00100, Kenya;
| | - Mohamed Hafidi
- AgroBioSciences Program, Mohammed VI Polytechnic University (UM6P), Benguerir 43150, Morocco; (M.H.); (Y.O.); (L.K.)
- Laboratory of Microbial Biotechnologies, Agrosciences and Environment, Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakesh 40000, Morocco
| | - Yedir Ouhdouch
- AgroBioSciences Program, Mohammed VI Polytechnic University (UM6P), Benguerir 43150, Morocco; (M.H.); (Y.O.); (L.K.)
- Laboratory of Microbial Biotechnologies, Agrosciences and Environment, Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakesh 40000, Morocco
| | | | - Lamfeddal Kouisni
- AgroBioSciences Program, Mohammed VI Polytechnic University (UM6P), Benguerir 43150, Morocco; (M.H.); (Y.O.); (L.K.)
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Gawin A, Tietze L, Aarstad OA, Aachmann FL, Brautaset T, Ertesvåg H. Functional characterization of three Azotobacter chroococcum alginate-modifying enzymes related to the Azotobacter vinelandii AlgE mannuronan C-5-epimerase family. Sci Rep 2020; 10:12470. [PMID: 32719381 PMCID: PMC7385640 DOI: 10.1038/s41598-020-68789-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 07/01/2020] [Indexed: 12/19/2022] Open
Abstract
Bacterial alginate initially consists of 1–4-linked β-D-mannuronic acid residues (M) which can be later epimerized to α-L-guluronic acid (G). The family of AlgE mannuronan C-5-epimerases from Azotobacter vinelandii has been extensively studied, and three genes putatively encoding AlgE-type epimerases have recently been identified in the genome of Azotobacter chroococcum. The three A. chroococcum genes, here designated AcalgE1, AcalgE2 and AcalgE3, were recombinantly expressed in Escherichia coli and the gene products were partially purified. The catalytic activities of the enzymes were stimulated by the addition of calcium ions in vitro. AcAlgE1 displayed epimerase activity and was able to introduce long G-blocks in the alginate substrate, preferentially by attacking M residues next to pre-existing G residues. AcAlgE2 and AcAlgE3 were found to display lyase activities with a substrate preference toward M-alginate. AcAlgE2 solely accepted M residues in the positions − 1 and + 2 relative to the cleavage site, while AcAlgE3 could accept either M or G residues in these two positions. Both AcAlgE2 and AcAlgE3 were bifunctional and could also catalyze epimerization of M to G. Together, we demonstrate that A. chroococcum encodes three different AlgE-like alginate-modifying enzymes and the biotechnological and biological impact of these findings are discussed.
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Affiliation(s)
- Agnieszka Gawin
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Lisa Tietze
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Olav A Aarstad
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Finn L Aachmann
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Trygve Brautaset
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Helga Ertesvåg
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway.
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Kretschmer M, Lieleg O. Chelate chemistry governs ion-specific stiffening of Bacillus subtilis B-1 and Azotobacter vinelandii biofilms. Biomater Sci 2020; 8:1923-1933. [PMID: 32031543 DOI: 10.1039/c9bm01763a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Unwanted formation of bacterial biofilms can cause problems in both the medical sector and industrial settings. However, removing them from surfaces remains an ongoing challenge since biofilm bacteria efficiently protect themselves from external influences such as mechanical shear forces by embedding themselves into a matrix of extracellular polymeric substances. Here, we discuss microscopic principles, which are responsible for alterations in the viscoelastic properties of biofilms upon contact with metal ions. We suggest that it is a combination of mainly two parameters, that decides if biofilm stiffening occurs or not: the ion size and the detailed configuration of polyanionic macromolecules from the biofilm matrix. Our results provide new insights in the molecular mechanisms that govern the mechanical properties of biofilms. Also, they indicate that hydrogels comprising purified biopolymers can serve as suitable model systems to reproduce certain aspects of biofilm mechanics - provided that the correct biopolymer is chosen.
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Affiliation(s)
- Martin Kretschmer
- Munich School of Bioengineering and Department of Mechanical Engineering, Technical University of Munich, 85748 Garching, Germany.
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42
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Biglari N, Orita I, Fukui T, Sudesh K. A study on the effects of increment and decrement repeated fed-batch feeding of glucose on the production of poly(3-hydroxybutyrate) [P(3HB)] by a newly engineered Cupriavidus necator NSDG-GG mutant in batch fill-and-draw fermentation. J Biotechnol 2020; 307:77-86. [DOI: 10.1016/j.jbiotec.2019.10.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/19/2019] [Accepted: 10/21/2019] [Indexed: 12/23/2022]
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43
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Ryu MH, Zhang J, Toth T, Khokhani D, Geddes BA, Mus F, Garcia-Costas A, Peters JW, Poole PS, Ané JM, Voigt CA. Control of nitrogen fixation in bacteria that associate with cereals. Nat Microbiol 2019; 5:314-330. [DOI: 10.1038/s41564-019-0631-2] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 11/04/2019] [Indexed: 12/23/2022]
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Quantifying Oxygen Management and Temperature and Light Dependencies of Nitrogen Fixation by Crocosphaera watsonii. mSphere 2019; 4:4/6/e00531-19. [PMID: 31826967 PMCID: PMC6908418 DOI: 10.1128/msphere.00531-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Crocosphaera is a major dinitrogen (N2)-fixing microorganism, providing bioavailable nitrogen (N) to marine ecosystems. The N2-fixing enzyme nitrogenase is deactivated by oxygen (O2), which is abundant in marine environments. Using a cellular scale model of Crocosphaera sp. and laboratory data, we quantify the role of three O2 management strategies by Crocosphaera sp.: size adjustment, reduced O2 diffusivity, and respiratory protection. Our model predicts that Crocosphaera cells increase their size under high O2 Using transmission electron microscopy, we show that starch granules and thylakoid membranes are located near the cytoplasmic membranes, forming a barrier for O2 The model indicates a critical role for respiration in protecting the rate of N2 fixation. Moreover, the rise in respiration rates and the decline in ambient O2 with temperature strengthen this mechanism in warmer water, providing a physiological rationale for the observed niche of Crocosphaera at temperatures exceeding 20°C. Our new measurements of the sensitivity to light intensity show that the rate of N2 fixation reaches saturation at a lower light intensity (∼100 μmol m-2 s-1) than photosynthesis and that both are similarly inhibited by light intensities of >500 μmol m-2 s-1 This suggests an explanation for the maximum population of Crocosphaera occurring slightly below the ocean surface.IMPORTANCE Crocosphaera is one of the major N2-fixing microorganisms in the open ocean. On a global scale, the process of N2 fixation is important in balancing the N budget, but the factors governing the rate of N2 fixation remain poorly resolved. Here, we combine a mechanistic model and both previous and present laboratory studies of Crocosphaera to quantify how chemical factors such as C, N, Fe, and O2 and physical factors such as temperature and light affect N2 fixation. Our study shows that Crocosphaera combines multiple mechanisms to reduce intracellular O2 to protect the O2-sensitive N2-fixing enzyme. Our model, however, indicates that these protections are insufficient at low temperature due to reduced respiration and the rate of N2 fixation becomes severely limited. This provides a physiological explanation for why the geographic distribution of Crocosphaera is confined to the warm low-latitude ocean.
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Abstract
Rhizobia are α- and β-proteobacteria that form a symbiotic partnership with legumes, fixing atmospheric dinitrogen to ammonia and providing it to the plant. Oxygen regulation is key in this symbiosis. Fixation is performed by an oxygen-intolerant nitrogenase enzyme but requires respiration to meet its high energy demands. To satisfy these opposing constraints the symbiotic partners cooperate intimately, employing a variety of mechanisms to regulate and respond to oxygen concentration. During symbiosis rhizobia undergo significant changes in gene expression to differentiate into nitrogen-fixing bacteroids. Legumes host these bacteroids in specialized root organs called nodules. These generate a near-anoxic environment using an oxygen diffusion barrier, oxygen-binding leghemoglobin and control of mitochondria localization. Rhizobia sense oxygen using multiple interconnected systems which enable a finely-tuned response to the wide range of oxygen concentrations they experience when transitioning from soil to nodules. The oxygen-sensing FixL-FixJ and hybrid FixL-FxkR two-component systems activate at relatively high oxygen concentration and regulate fixK transcription. FixK activates the fixNOQP and fixGHIS operons producing a high-affinity terminal oxidase required for bacterial respiration in the microaerobic nodule. Additionally or alternatively, some rhizobia regulate expression of these operons by FnrN, an FNR-like oxygen-sensing protein. The final stage of symbiotic establishment is activated by the NifA protein, regulated by oxygen at both the transcriptional and protein level. A cross-species comparison of these systems highlights differences in their roles and interconnections but reveals common regulatory patterns and themes. Future work is needed to establish the complete regulon of these systems and identify other regulatory signals.
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Affiliation(s)
- Paul J Rutten
- 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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46
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Liu J, Yang S, Li X, Yan Q, Reaney MJT, Jiang Z. Alginate Oligosaccharides: Production, Biological Activities, and Potential Applications. Compr Rev Food Sci Food Saf 2019; 18:1859-1881. [DOI: 10.1111/1541-4337.12494] [Citation(s) in RCA: 104] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 07/09/2019] [Accepted: 07/29/2019] [Indexed: 12/15/2022]
Affiliation(s)
- Jun Liu
- Beijing Advanced Innovation Center for Food Nutrition and Human HealthCollege of Food Science and Nutritional EngineeringChina Agricultural Univ. Beijing 100083 China
- Beijing Advanced Innovation Center for Food Nutrition and Human HealthBeijing Technology and Business Univ. Beijing 100048 China
| | - Shaoqing Yang
- Beijing Advanced Innovation Center for Food Nutrition and Human HealthCollege of Food Science and Nutritional EngineeringChina Agricultural Univ. Beijing 100083 China
| | - Xiuting Li
- Beijing Advanced Innovation Center for Food Nutrition and Human HealthBeijing Technology and Business Univ. Beijing 100048 China
| | - Qiaojuan Yan
- Bioresource Utilization LaboratoryCollege of EngineeringChina Agricultural Univ. Beijing 100083 China
| | - Martin J. T. Reaney
- Dept. of Plant SciencesUniv. of Saskatchewan Saskatoon SK S7N 5A8 Canada
- Guangdong Saskatchewan Oilseed Joint Laboratory (GUSTO)Dept. of Food Science and EngineeringJinan Univ. Guangzhou 510632 China
| | - Zhengqiang Jiang
- Beijing Advanced Innovation Center for Food Nutrition and Human HealthCollege of Food Science and Nutritional EngineeringChina Agricultural Univ. Beijing 100083 China
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47
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Wu C, Herold RA, Knoshaug EP, Wang B, Xiong W, Laurens LML. Fluxomic Analysis Reveals Central Carbon Metabolism Adaptation for Diazotroph Azotobacter vinelandii Ammonium Excretion. Sci Rep 2019; 9:13209. [PMID: 31520074 PMCID: PMC6744558 DOI: 10.1038/s41598-019-49717-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 08/30/2019] [Indexed: 11/09/2022] Open
Abstract
Diazotrophic bacteria are an attractive biological alternative to synthetic nitrogen fertilizers due to their remarkable capacity to fix atmospheric nitrogen gas to ammonium via nitrogenase enzymes. However, how diazotrophic bacteria tailor central carbon catabolism to accommodate the energy requirement for nitrogenase activity is largely unknown. In this study, we used Azotobacter vinelandii DJ and an ammonium excreting mutant, AV3 (ΔNifL), to investigate central carbon metabolism fluxes and central cell bioenergetics in response to ammonium availability and nitrogenase activity. Enabled by the powerful and reliable methodology of 13C-metabolic flux analysis, we show that the respiratory TCA cycle is upregulated in association with increased nitrogenase activity and causes a monotonic decrease in specific growth rate. Whereas the activity of the glycolytic Entner-Doudoroff pathway is positively correlated with the cell growth rate. These new observations are formulated into a 13C-metabolic flux model which further improves the understanding and interpretation of intracellular bioenergetics. This analysis leads to the conclusion that, under aerobic conditions, respiratory TCA metabolism is responsible for the supply of additional ATP and reducing equivalents required for elevated nitrogenase activity. This study provides a quantitative relationship between central carbon and nitrogen metabolism in an aerobic diazotroph for the first time.
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Affiliation(s)
- Chao Wu
- Bioenergy Science and Technology Directorate, National Renewable Energy Laboratory (NREL), 15013, Denver West Parkway, Golden, CO, 80401, USA
| | - Ryan A Herold
- Bioenergy Science and Technology Directorate, National Renewable Energy Laboratory (NREL), 15013, Denver West Parkway, Golden, CO, 80401, USA
| | - Eric P Knoshaug
- Bioenergy Science and Technology Directorate, National Renewable Energy Laboratory (NREL), 15013, Denver West Parkway, Golden, CO, 80401, USA
| | - Bo Wang
- Bioenergy Science and Technology Directorate, National Renewable Energy Laboratory (NREL), 15013, Denver West Parkway, Golden, CO, 80401, USA
| | - Wei Xiong
- Bioenergy Science and Technology Directorate, National Renewable Energy Laboratory (NREL), 15013, Denver West Parkway, Golden, CO, 80401, USA.
| | - Lieve M L Laurens
- Bioenergy Science and Technology Directorate, National Renewable Energy Laboratory (NREL), 15013, Denver West Parkway, Golden, CO, 80401, USA.
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The Pseudomonas stutzeri-Specific Regulatory Noncoding RNA NfiS Targets katB mRNA Encoding a Catalase Essential for Optimal Oxidative Resistance and Nitrogenase Activity. J Bacteriol 2019; 201:JB.00334-19. [PMID: 31262840 PMCID: PMC6755748 DOI: 10.1128/jb.00334-19] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 06/25/2019] [Indexed: 12/18/2022] Open
Abstract
Pseudomonas stutzeri A1501 is a versatile nitrogen-fixing bacterium capable of living in diverse environments and coping with various oxidative stresses. NfiS, a regulatory noncoding RNA (ncRNA) involved in the control of nitrogen fixation in A1501, was previously shown to be required for optimal resistance to H2O2; however, the precise role of NfiS and the target genes involved in the oxidative stress response is entirely unknown. In this work, we systematically investigated the NfiS-based mechanisms underlying the response of this bacterium to H2O2 at the cellular and molecular levels. A mutant strain carrying a deletion of nfiS showed significant downregulation of oxidative stress response genes, especially katB, a catalase gene, and oxyR, an essential regulator for transcription of catalase genes. Secondary structure prediction revealed two binding sites in NfiS for katB mRNA. Complementation experiments using truncated nfiS genes showed that each of two sites is functional, but not sufficient, for NfiS-mediated regulation of oxidative stress resistance and nitrogenase activities. Microscale thermophoresis assays further indicated direct base pairing between katB mRNA and NfiS at both sites 1 and 2, thus enhancing the half-life of the transcript. We also demonstrated that katB expression is dependent on OxyR and that both OxyR and KatB are essential for optimal oxidative stress resistance and nitrogenase activities. H2O2 at low concentrations was detoxified by KatB, leaving O2 as a by-product to support nitrogen fixation under O2-insufficient conditions. Moreover, our data suggest that the direct interaction between NfiS and katB mRNA is a conserved and widespread mechanism among P. stutzeri strains.IMPORTANCE Protection against oxygen damage is crucial for survival of nitrogen-fixing bacteria due to the extreme oxygen sensitivity of nitrogenase. This work exemplifies how the small ncRNA NfiS coordinates oxidative stress response and nitrogen fixation via base pairing with katB mRNA and nifK mRNA. Hence, NfiS acts as a molecular link to coordinate the expression of genes involved in oxidative stress response and nitrogen fixation. Our study provides the first insight into the biological functions of NfiS in oxidative stress regulation and adds a new regulation level to the mechanisms that contribute to the oxygen protection of the MoFe nitrogenase.
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Moreno S, Ertesvåg H, Valla S, Núñez C, Espin G, Cocotl-Yañez M. RpoS controls the expression and the transport of the AlgE1-7 epimerases in Azotobacter vinelandii. FEMS Microbiol Lett 2019; 365:5087732. [PMID: 30169849 PMCID: PMC6140867 DOI: 10.1093/femsle/fny210] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 08/27/2018] [Indexed: 12/23/2022] Open
Abstract
Azotobacter vinelandii produces differentiated cells, called cysts, surrounded by two alginate layers, which are necessary for their desiccation resistance. This alginate contains variable proportions of guluronate residues, resulting from the activity of seven extracytoplasmic epimerases, AlgE1-7. These enzymes are exported by a system secretion encoded by the eexDEF operon; mutants lacking the AlgE1-7 epimerases, the EexDEF or the RpoS sigma factor produce alginate, but are unable to form desiccation resistant cysts. Herein, we found that RpoS was required for full transcription of the algE1-7 and eexDEF genes. We found that the AlgE1-7 protein levels were diminished in the rpoS mutant strain. In addition, the alginate produced in the absence of RpoS was more viscous in the presence of proteases, a phenotype similar to that of the eexD mutant. Primer extension analysis located two promoters for the eexDEF operon, one of them was RpoS-dependent. Thus, during encysting conditions, RpoS coordinates the expression of both the AlgE1-7 epimerases and the EexDEF protein complex responsible for their transport.
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Affiliation(s)
- S Moreno
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México. Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos. C.P. 62210, México
| | - H Ertesvåg
- Department of Biotechnology and Food Science, NTNU-Norwegian University of Science and Technology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
| | - S Valla
- Department of Biotechnology and Food Science, NTNU-Norwegian University of Science and Technology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
| | - C Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México. Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos. C.P. 62210, México
| | - G Espin
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México. Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos. C.P. 62210, México
| | - M Cocotl-Yañez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México. Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos. C.P. 62210, México.,Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México. Ciudad de México. C.P. 04510, México
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Mus F, Colman DR, Peters JW, Boyd ES. Geobiological feedbacks, oxygen, and the evolution of nitrogenase. Free Radic Biol Med 2019; 140:250-259. [PMID: 30735835 DOI: 10.1016/j.freeradbiomed.2019.01.050] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 01/31/2019] [Indexed: 12/21/2022]
Abstract
Biological nitrogen fixation via the activity of nitrogenase is one of the most important biological innovations, allowing for an increase in global productivity that eventually permitted the emergence of higher forms of life. The complex metalloenzyme termed nitrogenase contains complex iron-sulfur cofactors. Three versions of nitrogenase exist that differ mainly by the presence or absence of a heterometal at the active site metal cluster (either Mo or V). Mo-dependent nitrogenase is the most common while V-dependent or heterometal independent (Fe-only) versions are often termed alternative nitrogenases since they have apparent lower activities for N2 reduction and are expressed in the absence of Mo. Phylogenetic data indicates that biological nitrogen fixation emerged in an anaerobic, thermophilic ancestor of hydrogenotrophic methanogens and later diversified via lateral gene transfer into anaerobic bacteria, and eventually aerobic bacteria including Cyanobacteria. Isotopic evidence suggests that nitrogenase activity existed at 3.2 Ga, prior to the advent of oxygenic photosynthesis and rise of oxygen in the atmosphere, implying the presence of favorable environmental conditions for oxygen-sensitive nitrogenase to evolve. Following the proliferation of oxygenic phototrophs, diazotrophic organisms had to develop strategies to protect nitrogenase from oxygen inactivation and generate the right balance of low potential reducing equivalents and cellular energy for growth and nitrogen fixation activity. Here we review the fundamental advances in our understanding of biological nitrogen fixation in the context of the emergence, evolution, and taxonomic distribution of nitrogenase, with an emphasis placed on key events associated with its emergence and diversification from anoxic to oxic environments.
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Affiliation(s)
- Florence Mus
- Institute of Biological Chemistry, Washington State University, Pullman, WA, USA
| | - Daniel R Colman
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA
| | - John W Peters
- Institute of Biological Chemistry, Washington State University, Pullman, WA, USA.
| | - Eric S Boyd
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA.
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