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Chowdhury-Paul S, Martínez-Ortíz IC, Pando-Robles V, Moreno S, Espín G, Merino E, Núñez C. The Azotobacter vinelandii AlgU regulon during vegetative growth and encysting conditions: A proteomic approach. PLoS One 2023; 18:e0286440. [PMID: 37967103 PMCID: PMC10651043 DOI: 10.1371/journal.pone.0286440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 10/24/2023] [Indexed: 11/17/2023] Open
Abstract
In the Pseduomonadacea family, the extracytoplasmic function sigma factor AlgU is crucial to withstand adverse conditions. Azotobacter vinelandii, a closed relative of Pseudomonas aeruginosa, has been a model for cellular differentiation in Gram-negative bacteria since it forms desiccation-resistant cysts. Previous work demonstrated the essential role of AlgU to withstand oxidative stress and on A. vinelandii differentiation, particularly for the positive control of alginate production. In this study, the AlgU regulon was dissected by a proteomic approach under vegetative growing conditions and upon encystment induction. Our results revealed several molecular targets that explained the requirement of this sigma factor during oxidative stress and extended its role in alginate production. Furthermore, we demonstrate that AlgU was necessary to produce alkyl resorcinols, a type of aromatic lipids that conform the cell membrane of the differentiated cell. AlgU was also found to positively regulate stress resistance proteins such as OsmC, LEA-1, or proteins involved in trehalose synthesis. A position-specific scoring-matrix (PSSM) was generated based on the consensus sequence recognized by AlgU in P. aeruginosa, which allowed the identification of direct AlgU targets in the A. vinelandii genome. This work further expands our knowledge about the function of the ECF sigma factor AlgU in A. vinelandii and contributes to explains its key regulatory role under adverse conditions.
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Affiliation(s)
- Sangita Chowdhury-Paul
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Iliana C. Martínez-Ortíz
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Victoria Pando-Robles
- Instituto Nacional de Salud Pública, Centro de Investigación Sobre Enfermedades Infecciosas, Cuernavaca, Morelos, México
| | - Soledad Moreno
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Guadalupe Espín
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Enrique Merino
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Cinthia Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
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Chuacharoen T, Aroonsong S, Chysirichote T. Alginate Production of Azotobacter vinelandii Using Sugar Cane Juice as the Main Carbon Source in an Airlift Bioreactor. Ind Eng Chem Res 2022. [DOI: 10.1021/acs.iecr.2c02693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Thanida Chuacharoen
- Faculty of Science and Technology, Suan Sunandha Rajabhat University, 1 U Thong Nok Rd, Dusit, Bangkok 10300, Thailand
| | - Soysruang Aroonsong
- Department of Food Engineering, School of Engineering, King Mongkut’s Institute of Technology Ladkrabang, 1 Chalongkrung 1, Chalongkrung Rd, Ladkrabang, Bangkok 10520 Thailand
| | - Teerin Chysirichote
- Department of Food Engineering, School of Engineering, King Mongkut’s Institute of Technology Ladkrabang, 1 Chalongkrung 1, Chalongkrung Rd, Ladkrabang, Bangkok 10520 Thailand
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Núñez C, López-Pliego L, Ahumada-Manuel CL, Castañeda M. Genetic Regulation of Alginate Production in Azotobacter vinelandii a Bacterium of Biotechnological Interest: A Mini-Review. Front Microbiol 2022; 13:845473. [PMID: 35401471 PMCID: PMC8988225 DOI: 10.3389/fmicb.2022.845473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 03/03/2022] [Indexed: 11/17/2022] Open
Abstract
Alginates are a family of polymers composed of guluronate and mannuronate monomers joined by β (1–4) links. The different types of alginates have variations in their monomer content and molecular weight, which determine the rheological properties and their applications. In industry, alginates are commonly used as additives capable of viscosifying, stabilizing, emulsifying, and gelling aqueous solutions. Recently, additional specialized biomedical uses have been reported for this polymer. Currently, the production of alginates is based on the harvesting of seaweeds; however, the composition and structure of the extracts are highly variable. The production of alginates for specialized applications requires a precise composition of monomers and molecular weight, which could be achieved using bacterial production systems such as those based on Azotobacter vinelandii, a free-living, non-pathogenic bacterium. In this mini-review, we analyze the latest advances in the regulation of alginate synthesis in this model.
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Affiliation(s)
- Cinthia Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Liliana López-Pliego
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Carlos Leonel Ahumada-Manuel
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Miguel Castañeda
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
- *Correspondence: Miguel Castañeda,
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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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Aasfar A, Bargaz A, Yaakoubi K, Hilali A, Bennis I, Zeroual Y, Meftah Kadmiri I. Nitrogen Fixing Azotobacter Species as Potential Soil Biological Enhancers for Crop Nutrition and Yield Stability. Front Microbiol 2021; 12:628379. [PMID: 33717018 PMCID: PMC7947814 DOI: 10.3389/fmicb.2021.628379] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 02/05/2021] [Indexed: 12/20/2022] Open
Abstract
Biological nitrogen fixation (BNF) refers to a microbial mediated process based upon an enzymatic "Nitrogenase" conversion of atmospheric nitrogen (N2) into ammonium readily absorbable by roots. N2-fixing microorganisms collectively termed as "diazotrophs" are able to fix biologically N2 in association with plant roots. Specifically, the symbiotic rhizobacteria induce structural and physiological modifications of bacterial cells and plant roots into specialized structures called nodules. Other N2-fixing bacteria are free-living fixers that are highly diverse and globally widespread in cropland. They represent key natural source of nitrogen (N) in natural and agricultural ecosystems lacking symbiotic N fixation (SNF). In this review, the importance of Azotobacter species was highlighted as both important free-living N2-fixing bacteria and potential bacterial biofertilizer with proven efficacy for plant nutrition and biological soil fertility. In addition, we described Azotobacter beneficial plant promoting traits (e.g., nutrient use efficiency, protection against phytopathogens, phytohormone biosynthesis, etc.). We shed light also on the agronomic features of Azotobacter that are likely an effective component of integrated plant nutrition strategy, which contributes positively to sustainable agricultural production. We pointed out Azotobacter based-biofertilizers, which possess unique characteristics such as cyst formation conferring resistance to environmental stresses. Such beneficial traits can be explored profoundly for the utmost aim to research and develop specific formulations based on inoculant Azotobacter cysts. Furthermore, Azotobacter species still need to be wisely exploited in order to address specific agricultural challenges (e.g., nutrient deficiencies, biotic and abiotic constraints) taking into consideration several variables including their biological functions, synergies and multi-trophic interactions, and biogeography and abundance distribution.
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Affiliation(s)
- Abderrahim Aasfar
- Green Biotechnology Laboratory, Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Rabat Design Centre, Rabat, Morocco.,Laboratory of Health Sciences and Technologies, High Institute of Health Sciences, Hassan 1st University, Settat, Morocco
| | - Adnane Bargaz
- AgroBioSciences-Microbiome, Laboratory of Plant-Microbe Interactions, Mohammed VI Polytechnic University, Ben Guerir, Morocco
| | - Kaoutar Yaakoubi
- Green Biotechnology Laboratory, Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Rabat Design Centre, Rabat, Morocco
| | - Abderraouf Hilali
- Laboratory of Health Sciences and Technologies, High Institute of Health Sciences, Hassan 1st University, Settat, Morocco
| | - Iman Bennis
- Green Biotechnology Laboratory, Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Rabat Design Centre, Rabat, Morocco
| | | | - Issam Meftah Kadmiri
- Green Biotechnology Laboratory, Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Rabat Design Centre, Rabat, Morocco.,AgroBioSciences-Microbiome, Laboratory of Plant-Microbe Interactions, Mohammed VI Polytechnic University, Ben Guerir, Morocco
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Cyclic di-GMP-Mediated Regulation of Extracellular Mannuronan C-5 Epimerases Is Essential for Cyst Formation in Azotobacter vinelandii. J Bacteriol 2020; 202:JB.00135-20. [PMID: 32989089 DOI: 10.1128/jb.00135-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 09/23/2020] [Indexed: 11/20/2022] Open
Abstract
The genus Azotobacter, belonging to the Pseudomonadaceae family, is characterized by the formation of cysts, which are metabolically dormant cells produced under adverse conditions and able to resist desiccation. Although this developmental process has served as a model for the study of cell differentiation in Gram-negative bacteria, the molecular basis of its regulation is still poorly understood. Here, we report that the ubiquitous second messenger cyclic dimeric GMP (c-di-GMP) is critical for the formation of cysts in Azotobacter vinelandii Upon encystment induction, the levels of c-di-GMP increased, reaching a peak within the first 6 h. In the absence of the diguanylate cyclase MucR, however, the levels of this second messenger remained low throughout the developmental process. A. vinelandii cysts are surrounded by two alginate layers with variable proportions of guluronic residues, which are introduced into the final alginate chain by extracellular mannuronic C-5 epimerases of the AlgE1 to AlgE7 family. Unlike in Pseudomonas aeruginosa, MucR was not required for alginate polymerization in A. vinelandii Conversely, MucR was necessary for the expression of extracellular alginate C-5 epimerases; therefore, the MucR-deficient strain produced cyst-like structures devoid of the alginate capsule and unable to resist desiccation. Expression of mucR was partially dependent on the response regulator AlgR, which binds to two sites in the mucR promoter, enhancing mucR transcription. Together, these results indicate that the developmental process of A. vinelandii is controlled through a signaling module that involves activation by the response regulator AlgR and c-di-GMP accumulation that depends on MucR.IMPORTANCE A. vinelandii has served as an experimental model for the study of the differentiation processes to form metabolically dormant cells in Gram-negative bacteria. This work identifies c-di-GMP as a critical regulator for the production of alginates with specific contents of guluronic residues that are able to structure the rigid laminated layers of the cyst envelope. Although allosteric activation of the alginate polymerase complex Alg8-Alg44 by c-di-GMP has long been recognized, our results show a previously unidentified role during the polymer modification step, controlling the expression of extracellular alginate epimerases. Our results also highlight the importance of c-di-GMP in the control of the physical properties of alginate, which ultimately determine the desiccation resistance of the differentiated cell.
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Mærk M, Jakobsen ØM, Sletta H, Klinkenberg G, Tøndervik A, Ellingsen TE, Valla S, Ertesvåg H. Identification of Regulatory Genes and Metabolic Processes Important for Alginate Biosynthesis in Azotobacter vinelandii by Screening of a Transposon Insertion Mutant Library. Front Bioeng Biotechnol 2020; 7:475. [PMID: 32010681 PMCID: PMC6979010 DOI: 10.3389/fbioe.2019.00475] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 12/23/2019] [Indexed: 12/23/2022] Open
Abstract
Azotobacter vinelandii produces the biopolymer alginate, which has a wide range of industrial and pharmaceutical applications. A random transposon insertion mutant library was constructed from A. vinelandii ATCC12518Tc in order to identify genes and pathways affecting alginate biosynthesis, and about 4,000 mutant strains were screened for altered alginate production. One mutant, containing a mucA disruption, displayed an elevated alginate production level, and several mutants with decreased or abolished alginate production were identified. The regulatory proteins AlgW and AmrZ seem to be required for alginate production in A. vinelandii, similarly to Pseudomonas aeruginosa. An algB mutation did however not affect alginate yield in A. vinelandii although its P. aeruginosa homolog is needed for full alginate production. Inactivation of the fructose phosphoenolpyruvate phosphotransferase system protein FruA resulted in a mutant that did not produce alginate when cultivated in media containing various carbon sources, indicating that this system could have a role in regulation of alginate biosynthesis. Furthermore, impaired or abolished alginate production was observed for strains with disruptions of genes involved in peptidoglycan biosynthesis/recycling and biosynthesis of purines, isoprenoids, TCA cycle intermediates, and various vitamins, suggesting that sufficient access to some of these compounds is important for alginate production. This hypothesis was verified by showing that addition of thiamine, succinate or a mixture of lysine, methionine and diaminopimelate increases alginate yield in the non-mutagenized strain. These results might be used in development of optimized alginate production media or in genetic engineering of A. vinelandii strains for alginate bioproduction.
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Affiliation(s)
- Mali Mærk
- Department of Biotechnology and Food Science, Norwegian University of Science and Technology, Trondheim, Norway
| | | | | | | | | | | | - Svein Valla
- Department of Biotechnology and Food Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Helga Ertesvåg
- Department of Biotechnology and Food Science, Norwegian University of Science and Technology, Trondheim, Norway
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Chowdhury-Paul S, Pando-Robles V, Jiménez-Jacinto V, Segura D, Espín G, Núñez C. Proteomic analysis revealed proteins induced upon Azotobacter vinelandii encystment. J Proteomics 2018; 181:47-59. [PMID: 29605291 DOI: 10.1016/j.jprot.2018.03.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 03/09/2018] [Accepted: 03/27/2018] [Indexed: 01/22/2023]
Affiliation(s)
- Sangita Chowdhury-Paul
- Departamento de Microbiología Molecular, Instituto de Biotecnología, UNAM, Av. Universidad, 2001, Col Chamilpa, C.P. 62210 Cuernavaca, Morelos, México
| | - Victoria Pando-Robles
- Instituto Nacional de Salud Pública, Centro de Investigación Sobre Enfermedades Infecciosas (CISEI), Universidad No. 655 Colonia Santa María Ahuacatitlán, Cerrada Los Pinos y Caminera, C.P. 62100 Cuernavaca, Morelos, México
| | - Verónica Jiménez-Jacinto
- Unidad Universitaria de Secuenciación Masiva y Bioinformática, Instituto de Biotecnologia, UNAM, Av. Universidad, 2001, Col Chamilpa, C.P. 62210 Cuernavaca, Morelos, México
| | - Daniel Segura
- Departamento de Microbiología Molecular, Instituto de Biotecnología, UNAM, Av. Universidad, 2001, Col Chamilpa, C.P. 62210 Cuernavaca, Morelos, México
| | - Guadalupe Espín
- Departamento de Microbiología Molecular, Instituto de Biotecnología, UNAM, Av. Universidad, 2001, Col Chamilpa, C.P. 62210 Cuernavaca, Morelos, México
| | - Cinthia Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, UNAM, Av. Universidad, 2001, Col Chamilpa, C.P. 62210 Cuernavaca, Morelos, México.
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Noar JD, Bruno-Bárcena JM. Azotobacter vinelandii: the source of 100 years of discoveries and many more to come. MICROBIOLOGY-SGM 2018. [PMID: 29533747 DOI: 10.1099/mic.0.000643] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Azotobacter vinelandii has been studied for over 100 years since its discovery as an aerobic nitrogen-fixing organism. This species has proved useful for the study of many different biological systems, including enzyme kinetics and the genetic code. It has been especially useful in working out the structures and mechanisms of different nitrogenase enzymes, how they can function in oxic environments and the interactions of nitrogen fixation with other aspects of metabolism. Interest in studying A. vinelandii has waned in recent decades, but this bacterium still possesses great potential for new discoveries in many fields and commercial applications. The species is of interest for research because of its genetic pliability and natural competence. Its features of particular interest to industry are its ability to produce multiple valuable polymers - bioplastic and alginate in particular; its nitrogen-fixing prowess, which could reduce the need for synthetic fertilizer in agriculture and industrial fermentations, via coculture; its production of potentially useful enzymes and metabolic pathways; and even its biofuel production abilities. This review summarizes the history and potential for future research using this versatile microbe.
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Affiliation(s)
- Jesse D Noar
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA
| | - Jose M Bruno-Bárcena
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA
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Gangoiti J, van Leeuwen SS, Vafiadi C, Dijkhuizen L. The Gram-negative bacterium Azotobacter chroococcum NCIMB 8003 employs a new glycoside hydrolase family 70 4,6-α-glucanotransferase enzyme (GtfD) to synthesize a reuteran like polymer from maltodextrins and starch. Biochim Biophys Acta Gen Subj 2016; 1860:1224-36. [DOI: 10.1016/j.bbagen.2016.02.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 02/04/2016] [Accepted: 02/05/2016] [Indexed: 10/22/2022]
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Robson RL, Jones R, Robson RM, Schwartz A, Richardson TH. Azotobacter Genomes: The Genome of Azotobacter chroococcum NCIMB 8003 (ATCC 4412). PLoS One 2015; 10:e0127997. [PMID: 26061173 PMCID: PMC4465626 DOI: 10.1371/journal.pone.0127997] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Accepted: 04/22/2015] [Indexed: 11/18/2022] Open
Abstract
The genome of the soil-dwelling heterotrophic N2-fixing Gram-negative bacterium Azotobacter chroococcum NCIMB 8003 (ATCC 4412) (Ac-8003) has been determined. It consists of 7 circular replicons totalling 5,192,291 bp comprising a circular chromosome of 4,591,803 bp and six plasmids pAcX50a, b, c, d, e, f of 10,435 bp, 13,852, 62,783, 69,713, 132,724, and 311,724 bp respectively. The chromosome has a G+C content of 66.27% and the six plasmids have G+C contents of 58.1, 55.3, 56.7, 59.2, 61.9, and 62.6% respectively. The methylome has also been determined and 5 methylation motifs have been identified. The genome also contains a very high number of transposase/inactivated transposase genes from at least 12 of the 17 recognised insertion sequence families. The Ac-8003 genome has been compared with that of Azotobacter vinelandii ATCC BAA-1303 (Av-DJ), a derivative of strain O, the only other member of the Azotobacteraceae determined so far which has a single chromosome of 5,365,318 bp and no plasmids. The chromosomes show significant stretches of synteny throughout but also reveal a history of many deletion/insertion events. The Ac-8003 genome encodes 4628 predicted protein-encoding genes of which 568 (12.2%) are plasmid borne. 3048 (65%) of these show > 85% identity to the 5050 protein-encoding genes identified in Av-DJ, and of these 99 are plasmid-borne. The core biosynthetic and metabolic pathways and macromolecular architectures and machineries of these organisms appear largely conserved including genes for CO-dehydrogenase, formate dehydrogenase and a soluble NiFe-hydrogenase. The genetic bases for many of the detailed phenotypic differences reported for these organisms have also been identified. Also many other potential phenotypic differences have been uncovered. Properties endowed by the plasmids are described including the presence of an entire aerobic corrin synthesis pathway in pAcX50f and the presence of genes for retro-conjugation in pAcX50c. All these findings are related to the potentially different environmental niches from which these organisms were isolated and to emerging theories about how microbes contribute to their communities.
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Affiliation(s)
- Robert L. Robson
- School of Biological Sciences, University of Reading, Whiteknights, Reading, United Kingdom
| | - Robert Jones
- Craic Computing LLC, Seattle, Washington, United States of America
| | - R. Moyra Robson
- School of Biological Sciences, University of Reading, Whiteknights, Reading, United Kingdom
| | - Ariel Schwartz
- Synthetic Genomics, La Jolla, California, United States of America
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Okkotsu Y, Little AS, Schurr MJ. The Pseudomonas aeruginosa AlgZR two-component system coordinates multiple phenotypes. Front Cell Infect Microbiol 2014; 4:82. [PMID: 24999454 PMCID: PMC4064291 DOI: 10.3389/fcimb.2014.00082] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 06/02/2014] [Indexed: 01/28/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that causes a multitude of infections. These infections can occur at almost any site in the body and are usually associated with a breach of the innate immune system. One of the prominent sites where P. aeruginosa causes chronic infections is within the lungs of cystic fibrosis patients. P. aeruginosa uses two-component systems that sense environmental changes to differentially express virulence factors that cause both acute and chronic infections. The P. aeruginosa AlgZR two component system is one of its global regulatory systems that affects the organism's fitness in a broad manner. This two-component system is absolutely required for two P. aeruginosa phenotypes: twitching motility and alginate production, indicating its importance in both chronic and acute infections. Additionally, global transcriptome analyses indicate that it regulates the expression of many different genes, including those associated with quorum sensing, type IV pili, type III secretion system, anaerobic metabolism, cyanide and rhamnolipid production. This review examines the complex AlgZR regulatory network, what is known about the structure and function of each protein, and how it relates to the organism's ability to cause infections.
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Affiliation(s)
- Yuta Okkotsu
- Department of Microbiology, University of Colorado School of Medicine Aurora, CO, USA
| | - Alexander S Little
- Department of Microbiology, University of Colorado School of Medicine Aurora, CO, USA
| | - Michael J Schurr
- Department of Microbiology, University of Colorado School of Medicine Aurora, CO, USA
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Hay ID, Wang Y, Moradali MF, Rehman ZU, Rehm BHA. Genetics and regulation of bacterial alginate production. Environ Microbiol 2014; 16:2997-3011. [DOI: 10.1111/1462-2920.12389] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Revised: 12/18/2013] [Accepted: 12/22/2013] [Indexed: 12/31/2022]
Affiliation(s)
- Iain D. Hay
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
| | - Yajie Wang
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
| | - Mohammed F. Moradali
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
| | - Zahid U. Rehman
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
| | - Bernd H. A. Rehm
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology; Massey University; Palmerston North 4442 New Zealand
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14
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Sigma factor RpoS controls alkylresorcinol synthesis through ArpR, a LysR-type regulatory protein, during encystment of Azotobacter vinelandii. J Bacteriol 2013; 195:1834-44. [PMID: 23378510 DOI: 10.1128/jb.01946-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Azotobacter vinelandii is a bacterium which undergoes a differentiation process leading to the formation of metabolically dormant cysts. During the encystment process, A. vinelandii produces alkylresorcinol lipids (ARs) that replace the membrane phospholipids and are also components of the layers covering the cyst. The synthesis of ARs in A. vinelandii has been shown to occur by the activity of enzymes encoded by the arsABCD operon, which is expressed only during the differentiation process. Also, the production of ARs has been shown to be dependent on the stationary-phase sigma factor RpoS, which is also implicated in the control of the synthesis of other cyst components (i.e., alginate and poly-β-hydroxybutyrate). In this study, we identified ArpR, a LysR-type transcriptional regulator expressed only during encystment that positively regulates arsABCD transcription. We show that this activation is dependent on acetoacetyl-coenzyme A (acetoacetyl-CoA), which might provide a metabolic signal for encystment. We also show that RpoS regulates arsABCD expression through the control of arpR transcription.
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Paletta JL, Ohman DE. Evidence for Two Promoters Internal to the Alginate Biosynthesis Operon in Pseudomonas aeruginosa. Curr Microbiol 2012; 65:770-5. [DOI: 10.1007/s00284-012-0228-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 08/18/2012] [Indexed: 11/24/2022]
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16
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Genome sequence of Azotobacter vinelandii, an obligate aerobe specialized to support diverse anaerobic metabolic processes. J Bacteriol 2009; 191:4534-45. [PMID: 19429624 DOI: 10.1128/jb.00504-09] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Azotobacter vinelandii is a soil bacterium related to the Pseudomonas genus that fixes nitrogen under aerobic conditions while simultaneously protecting nitrogenase from oxygen damage. In response to carbon availability, this organism undergoes a simple differentiation process to form cysts that are resistant to drought and other physical and chemical agents. Here we report the complete genome sequence of A. vinelandii DJ, which has a single circular genome of 5,365,318 bp. In order to reconcile an obligate aerobic lifestyle with exquisitely oxygen-sensitive processes, A. vinelandii is specialized in terms of its complement of respiratory proteins. It is able to produce alginate, a polymer that further protects the organism from excess exogenous oxygen, and it has multiple duplications of alginate modification genes, which may alter alginate composition in response to oxygen availability. The genome analysis identified the chromosomal locations of the genes coding for the three known oxygen-sensitive nitrogenases, as well as genes coding for other oxygen-sensitive enzymes, such as carbon monoxide dehydrogenase and formate dehydrogenase. These findings offer new prospects for the wider application of A. vinelandii as a host for the production and characterization of oxygen-sensitive proteins.
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Núñez C, Bogachev AV, Guzmán G, Tello I, Guzmán J, Espín G. The Na+-translocating NADH : ubiquinone oxidoreductase of Azotobacter vinelandii negatively regulates alginate synthesis. Microbiology (Reading) 2009; 155:249-256. [DOI: 10.1099/mic.0.022533-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Azotobacter vinelandii is a nitrogen-fixing soil bacterium that produces the exopolysaccharide alginate. In this report we describe the isolation and characterization of A. vinelandii strain GG4, which carries an nqrE : : Tn5 mutation resulting in alginate overproduction. The nqrE gene encodes a subunit of the Na+-translocating NADH : ubiquinone oxidoreductase (Na+-NQR). As expected, Na+-NQR activity was abolished in mutant GG4. When this strain was complemented with the nqrEF genes this activity was restored and alginate production was reduced to wild-type levels. Na+-NQR may be the main sodium pump of A. vinelandii under the conditions tested (∼2 mM Na+) since no Na+/H+-antiporter activity was detected. Collectively our results indicate that in A. vinelandii the lack of Na+-NQR activity caused the absence of a transmembrane Na+ gradient and an increase in alginate production.
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Affiliation(s)
- Cinthia Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico
| | - Alexander V. Bogachev
- Department of Molecular Energetics of Microorganisms, A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia
| | - Gabriel Guzmán
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico
| | - Isaac Tello
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico
| | - Josefina Guzmán
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico
| | - Guadalupe Espín
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico
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18
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García-Esquivel G, Calva-Calva G, Ferrera-Cerrato R, Fernández-Linares LC, Vázquez RR, Esparza-García FJ. Encystment of Azotobacter nigricans grown diazotrophically on kerosene as sole carbon source. Arch Microbiol 2008; 191:275-81. [PMID: 19018516 DOI: 10.1007/s00203-008-0444-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Revised: 09/09/2008] [Accepted: 10/27/2008] [Indexed: 11/29/2022]
Abstract
Encystment of Azotobacter nigricans was induced by its diazotrophic cultivation on kerosene. Its growth and nitrogenase activity were affected by kerosene in comparison to cultures grown on sucrose. Electron microscopy of vegetative cells showed that when nitrogenase activity was higher and the poly-beta-hydroxybutyrate granules were not present to a significant extent, peripheral bodies were abundant. After 8 days of culture on kerosene, the presence of cysts with intracellular bunches of poly-beta-hydroxybutyrate granules was observed. Germination of cysts bears germinating multicelled yet unbroken capsule cysts with up to three cells inside. This is the first report of encystment induction of Azotobacter species grown on kerosene.
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Affiliation(s)
- Gabriela García-Esquivel
- Biotechnology and Bioengineering Department, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, C. P. 07360 Mexico D. F., Mexico
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19
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Muhammadi, Ahmed N. Genetics of bacterial alginate: alginate genes distribution, organization and biosynthesis in bacteria. Curr Genomics 2007; 8:191-202. [PMID: 18645604 PMCID: PMC2435354 DOI: 10.2174/138920207780833810] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Revised: 02/26/2007] [Accepted: 03/21/2007] [Indexed: 11/22/2022] Open
Abstract
Bacterial alginate genes are chromosomal and fairly widespread among rRNA homology group I Pseudomonads and Azotobacter. In both genera, the genetic pathway of alginate biosynthesis is mostly similar and the identified genes are identically organized into biosynthetic, regulatory and genetic switching clusters. In spite of these similarities,still there are transcriptional and functional variations between P. aeruginosa and A. vinelandii. In P. aeruginosa all biosynthetic genes except algC transcribe in polycistronic manner under the control of algD promoter while in A. vinelandii, these are organized into many transcriptional units. Of these, algA and algC are transcribed each from two different and algD from three different promoters. Unlike P. aeruginosa, the promoters of these transcriptional units except one of algC and algD are algT-independent. Both bacterial species carry homologous algG gene for Ca(2+)-independent epimerization. But besides algG, A. vinelandii also has algE1-7 genes which encode C-5-epimerases involved in the complex steps of Ca(2+)-dependent epimerization. A hierarchy of alginate genes expression under sigma(22)(algT) control exists in P. aeruginosa where algT is required for transcription of the response regulators algB and algR, which in turn are necessary for expression of algD and its downstream biosynthetic genes. Although algTmucABCD genes cluster play similar regulatory roles in both P. aeruginosa and A. vinelandii but unlike, transcription of A. vinelandii, algR is independent of sigma(22). These differences could be due to the fact that in A. vinelandii alginate plays a role as an integrated part in desiccation-resistant cyst which is not found in P. aeruginosa.
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Affiliation(s)
| | - Nuzhat Ahmed
- Centre for Molecular Genetics, University of Karachi, Karachi-75270,
Pakistan
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20
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Galindo E, Peña C, Núñez C, Segura D, Espín G. Molecular and bioengineering strategies to improve alginate and polydydroxyalkanoate production by Azotobacter vinelandii. Microb Cell Fact 2007; 6:7. [PMID: 17306024 PMCID: PMC1805506 DOI: 10.1186/1475-2859-6-7] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Accepted: 02/16/2007] [Indexed: 12/01/2022] Open
Abstract
Several aspects of alginate and PHB synthesis in Azotobacter vinelandii at a molecular level have been elucidated in articles published during the last ten years. It is now clear that alginate and PHB synthesis are under a very complex genetic control. Genetic modification of A. vinelandii has produced a number of very interesting mutants which have particular traits for alginate production. One of these mutants has been shown to produce the alginate with the highest mean molecular mass so far reported. Recent work has also shed light on the factors determining molecular mass distribution; the most important of these being identified as; dissolved oxygen tension and specific growth rate. The use of specific mutants has been very useful for the correct analysis and interpretation of the factors affecting polymerization. Recent scale-up/down work on alginate production has shown that oxygen limitation is crucial for producing alginate of high molecular mass, a condition which is optimized in shake flasks and which can now be reproduced in stirred fermenters. It is clear that the phenotypes of mutants grown on plates are not necessarily reproducible when the strains are tested in lab or bench scale fermenters. In the case of PHB, A. vinelandii has shown itself able to produce relatively large amounts of this polymer of high molecular weight on cheap substrates, even allowing for simple extraction processes. The development of fermentation strategies has also shown promising results in terms of improving productivity. The understanding of the regulatory mechanisms involved in the control of PHB synthesis, and of its metabolic relationships, has increased considerably, making way for new potential strategies for the further improvement of PHB production. Overall, the use of a multidisciplinary approach, integrating molecular and bioengineering aspects is a necessity for optimizing alginate and PHB production in A. vinelandii.
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Affiliation(s)
- Enrique Galindo
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional, Autónoma de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Carlos Peña
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional, Autónoma de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Cinthia Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma, de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Daniel Segura
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma, de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Guadalupe Espín
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma, de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
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21
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Berleman JE, Hasselbring BM, Bauer CE. Hypercyst mutants in Rhodospirillum centenum identify regulatory loci involved in cyst cell differentiation. J Bacteriol 2004; 186:5834-41. [PMID: 15317789 PMCID: PMC516826 DOI: 10.1128/jb.186.17.5834-5841.2004] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rhodospirillum centenum is a purple photosynthetic bacterium that forms resting cyst cells when starved for nutrients. In this study, we demonstrate that chalcone synthase gene (chsA) expression is developmentally regulated, with expression of chsA increasing up to 86-fold upon induction of the cyst developmental cycle. Screening for mini-Tn5-induced mutants that exhibit elevated chsA::lacZ expression has led to the isolation of a set of R. centenum mutants that display increased chsA gene expression concomitant with constitutive induction of the cyst developmental cycle. These "hypercyst" mutants have lost the ability to regulate cyst cell formation in response to nutrient availability. Sequence analysis indicates that the mini-Tn5-disrupted genes code for a variety of factors, including metabolic enzymes and a large set of potential regulatory factors, including four gene products with homology to histidine sensor kinases and three with homology to response regulators. Several of the disrupted genes also have sequence similarity to che-like signal transduction components.
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Affiliation(s)
- James E Berleman
- Department of Biology, Indiana University, Myers Hall, 915 E. Third St., Bloomington, IN 47405, USA
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22
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Núñez C, Adams L, Childers S, Lovley DR. The RpoS sigma factor in the dissimilatory Fe(III)-reducing bacterium Geobacter sulfurreducens. J Bacteriol 2004; 186:5543-6. [PMID: 15292160 PMCID: PMC490870 DOI: 10.1128/jb.186.16.5543-5546.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Geobacter sulfurreducens RpoS sigma factor was shown to contribute to survival in stationary phase and upon oxygen exposure. Furthermore, a mutation in rpoS decreased the rate of reduction of insoluble Fe(III) but not of soluble forms of iron. This study suggests that RpoS plays a role in regulating metabolism of Geobacter under suboptimal conditions in subsurface environments.
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Affiliation(s)
- Cinthia Núñez
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
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23
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Gaona G, Núñez C, Goldberg JB, Linford AS, Nájera R, Castañeda M, Guzmán J, EspÃn G, Soberón-Chávez G. Characterization of the Azotobacter vinelandii algCgene involved in alginate and lipopolysaccharide production. FEMS Microbiol Lett 2004. [DOI: 10.1111/j.1574-6968.2004.tb09756.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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24
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Grangeasse C, Obadia B, Mijakovic I, Deutscher J, Cozzone AJ, Doublet P. Autophosphorylation of the Escherichia coli protein kinase Wzc regulates tyrosine phosphorylation of Ugd, a UDP-glucose dehydrogenase. J Biol Chem 2003; 278:39323-9. [PMID: 12851388 DOI: 10.1074/jbc.m305134200] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Autophosphorylation of protein-tyrosine kinases (PTKs) involved in exopolysaccharide and capsular polysaccharide biosynthesis and transport has been observed in a number of Gram-negative and Gram-positive bacteria. However, besides their own phosphorylation, little is known about other substrates targeted by these protein-modifying enzymes. Here, we present evidence that the protein-tyrosine kinase Wzc of Escherichia coli is able to phosphorylate an endogenous enzyme, UDP-glucose dehydrogenase (Ugd), which participates in the synthesis of the exopolysaccharide colanic acid. The process of phosphorylation of Ugd by Wzc was shown to be stimulated by previous autophosphorylation of Wzc on tyrosine 569. The phosphorylation of Ugd was demonstrated to actually occur on tyrosine and result in a significant increase of its dehydrogenase activity. In addition, the phosphotyrosine-protein phosphatase Wzb, which is known to effectively dephosphorylate Wzc, exhibited only a low effect, if any, on the dephosphorylation of Ugd. These data were related to the recent observation that two other UDP-glucose dehydrogenases have been also shown to be phosphorylated by a PTK in the Gram-positive bacterium Bacillus subtilis. Comparative analysis of the activities of PTKs from Gram-negative and Gram-positive bacteria showed that they are regulated by different mechanisms that involve, respectively, either the autophosphorylation of kinases or their interaction with a membrane protein activator.
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Affiliation(s)
- Christophe Grangeasse
- Institut de Biologie et Chimie des Protéines, CNRS, Université de Lyon, 69367 Lyon Cedex 07, France.
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25
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Heulin T, Barakat M, Christen R, Lesourd M, Sutra L, De Luca G, Achouak W. Ramlibacter tataouinensis gen. nov., sp. nov., and Ramlibacter henchirensis sp. nov., cyst-producing bacteria isolated from subdesert soil in Tunisia. Int J Syst Evol Microbiol 2003; 53:589-594. [PMID: 12710631 DOI: 10.1099/ijs.0.02482-0] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ramlibacter gen. nov. is proposed for two aerobic, chemo-organotrophic, cyst-producing soil bacterial strains. These bacteria are Gram-negative, non-flagellated rods or cysts, isolated from subdesert soil in Tataouine, Tunisia. Phylogenetic analyses of the rrs sequences of the two strains showed that they do not constitute a robust clade at the genus level with any previously described bacteria and that they are a deep branch of a clade also grouping the genera Acidovorax and Hydrogenophaga within the beta-Proteobacteria. They belong to two different species, as verified by DNA-DNA hybridization (23.5% reassociation). The type species of the genus is Ramlibacter tataouinensis sp. nov., with the type strain TTB310T (=DSM 14655T =ATCC BAA-407T =LMG 21543T). The second species is Ramlibacter henchirensis sp. nov., with the type strain TMB834T (=DSM 14656T =ATCC BAA-408T =LMG 21542T). The G + C contents of R. tataouinensis and R. henchirensis are 69.6 and 66.6 mol%, respectively.
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Affiliation(s)
- Thierry Heulin
- CEA/Cadarache, DSV-DEVM, Laboratoire d'Ecologie Microbienne de la Rhizosphère UMR 163 CNRS-CEA-Univ. Méditerranée, F-13108 Saint-Paul-lez-Durance, France
| | - Mohamed Barakat
- CEA/Cadarache, DSV-DEVM, Laboratoire d'Ecologie Microbienne de la Rhizosphère UMR 163 CNRS-CEA-Univ. Méditerranée, F-13108 Saint-Paul-lez-Durance, France
| | - Richard Christen
- UMR 6078 CNRS-Université de Nice Sophia-Antipolis, Bât. Jean Maetz, F-06230 Villefranche-sur-mer, France
| | - Maurice Lesourd
- Service Commun de Microscopie Electronique, CNRS & Université d'Angers, rue Haute de Reculée, F-49045 Angers, France
| | - Laurent Sutra
- UMR 077 de Pathologie Végétale, INRA-INH-Université d'Angers, 42 rue Georges-Morel, BP 57, F-49071 Beaucouzé Cedex, France
| | - Gilles De Luca
- CEA/Cadarache, DSV-DEVM, Laboratoire d'Ecologie Microbienne de la Rhizosphère UMR 163 CNRS-CEA-Univ. Méditerranée, F-13108 Saint-Paul-lez-Durance, France
| | - Wafa Achouak
- CEA/Cadarache, DSV-DEVM, Laboratoire d'Ecologie Microbienne de la Rhizosphère UMR 163 CNRS-CEA-Univ. Méditerranée, F-13108 Saint-Paul-lez-Durance, France
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26
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Castañeda M, Sánchez J, Moreno S, Núñez C, Espín G. The global regulators GacA and sigma(S) form part of a cascade that controls alginate production in Azotobacter vinelandii. J Bacteriol 2001; 183:6787-93. [PMID: 11698366 PMCID: PMC95518 DOI: 10.1128/jb.183.23.6787-6793.2001] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcription of the Azotobacter vinelandii algD gene, which encodes GDP-mannose dehydrogenase (the rate-limiting enzyme of alginate synthesis), starts from three sites: p1, p2, and p3. The sensor kinase GacS, a member of the two-component regulatory system, is required for transcription of algD from its three sites during the stationary phase. Here we show that algD is expressed constitutively throughout the growth cycle from the p2 and p3 sites and that transcription from p1 started at the transition between the exponential growth phase and stationary phase. We constructed A. vinelandii strains that carried mutations in gacA encoding the cognate response regulator of GacS and in rpoS coding for the stationary-phase sigma(S) factor. The gacA mutation impaired alginate production and transcription of algD from its three promoters. Transcription of rpoS was also abolished by the gacA mutation. The rpoS mutation impaired transcription of algD from the p1 promoter and increased it from the p2 sigma(E) promoter. The results of this study provide evidence for the predominant role of GacA in a regulatory cascade controlling alginate production and gene expression during the stationary phase in A. vinelandii.
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Affiliation(s)
- M Castañeda
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca Morelos 62250, Mexico
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27
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Núñez C, León R, Guzmán J, Espín G, Soberón-Chávez G. Role of Azotobacter vinelandii mucA and mucC gene products in alginate production. J Bacteriol 2000; 182:6550-6. [PMID: 11073894 PMCID: PMC111392 DOI: 10.1128/jb.182.23.6550-6556.2000] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Azotobacter vinelandii produces the exopolysaccharide alginate, which is essential for its differentiation to desiccation-resistant cysts. In different bacterial species, the alternative sigma factor sigma(E) regulates the expression of functions related to the extracytoplasmic compartments. In A. vinelandii and Pseudomonas aeruginosa, the sigma(E) factor (AlgU) is essential for alginate production. In both bacteria, the activity of this sigma factor is regulated by the product of the mucA, mucB, mucC, and mucD genes. In this work, we studied the transcriptional regulation of the A. vinelandii algU-mucABCD gene cluster, as well as the role of the mucA and mucC gene products in alginate production. Our results show the existence of AlgU autoregulation and show that both MucA and MucC play a negative role in alginate production.
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Affiliation(s)
- C Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62251, Mexico
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28
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Núñez C, Moreno S, Cárdenas L, Soberón-Chávez G, Espín G. Inactivation of the ampDE operon increases transcription of algD and affects morphology and encystment of Azotobacter vinelandii. J Bacteriol 2000; 182:4829-35. [PMID: 10940024 PMCID: PMC111360 DOI: 10.1128/jb.182.17.4829-4835.2000] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcription of algD, encoding GDP-mannose dehydrogenase, the key enzyme in the alginate biosynthetic pathway, is highly regulated in Azotobacter vinelandii. We describe here the characterization of a Tn5 insertion mutant (AC28) which shows a higher level of expression of an algD::lacZ fusion. AC28 cells were morphologically abnormal and unable to encyst. The cloning and nucleotide sequencing of the Tn5-disrupted locus in AC28 revealed an operon homologous to the Escherichia coli ampDE operon. Tn5 was located within the ampD gene, encoding a cytosolic N-acetyl-anhydromuramyl-L-alanine amidase that participates in the intracellular recycling of peptidoglycan fragments. The ampE gene encodes a transmembrane protein, but the function of the protein is not known. We constructed strains carrying ampD or ampE mutations and one with an ampDE deletion. The strain with a deletion of the ampDE operon showed a phenotype similar to that of mutant AC28. The present work demonstrates that both alginate production and bacterial encystment are greatly influenced by the bacterial ability to recycle its cell wall.
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Affiliation(s)
- C Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca Morelos 62250, México
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29
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Sabra W, Zeng AP, Lünsdorf H, Deckwer WD. Effect of oxygen on formation and structure of Azotobacter vinelandii alginate and its role in protecting nitrogenase. Appl Environ Microbiol 2000; 66:4037-44. [PMID: 10966426 PMCID: PMC92256 DOI: 10.1128/aem.66.9.4037-4044.2000] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2000] [Accepted: 06/06/2000] [Indexed: 11/20/2022] Open
Abstract
The activity of nitrogenase in the nitrogen-fixing bacterium Azotobacter vinelandii grown diazotrophically under aerobic conditions is generally considered to be protected against O(2) by a high respiration rate. In this work, we have shown that a high rate of respiration is not the prevailing mechanism for nitrogenase protection in A. vinelandii grown in phosphate-limited nitrogen-free chemostat culture. Instead, the formation of alginate appeared to play a decisive role in protecting the nitrogenase that is required for cell growth in this culture. Depending on the O(2) tension and cell growth rate, the formation rate and composition of alginate released into the culture broth varied significantly. Furthermore, transmission electron microscopic analysis of cell morphology and the cell surface revealed the existence of an alginate capsule on the surface of A. vinelandii. The composition, thickness, and compactness of this alginate capsule also varied significantly. In general, increasing O(2) tension led to the formation of alginate with a higher molecular weight and a greater L-guluronic acid content. The alginate capsule was accordingly thicker and more compact. In addition, the formation of the alginate capsule was found to be strongly affected by the shear rate in a bioreactor. Based on these experimental results, it is suggested that the production of alginate, especially the formation of an alginate capsule on the cell surface, forms an effective barrier for O(2) transfer into the cell. It is obviously the quality, not the quantity, of alginate that is decisive for the protection of nitrogenase.
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Affiliation(s)
- W Sabra
- Biochemical Engineering Division, Gesellschaft für Biotechnologische Forschung mbH, 38124 Braunschweig, Germany
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30
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Vazquez A, Moreno S, Guzmán J, Alvarado A, Espín G. Transcriptional organization of the Azotobacter vinelandii algGXLVIFA genes: characterization of algF mutants. Gene X 1999; 232:217-22. [PMID: 10352233 DOI: 10.1016/s0378-1119(99)00119-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Azotobacter vinelandii forms desiccation-resistant cysts which contain a high proportion of the exopolysaccharide alginate in their envelope. We have previously shown that the A. vinelandii alginate biosynthetic genes algA and algL are transcribed from a promoter located somewhere upstream of algL. In this study we sequenced the A. vinelandii algX, algL, algV, algI and algF genes located between algG and algA. We carried out primer extension analysis of the algG, algX and algL genes and detected transcription start sites upstream algG but not upstream algX or algL, implying that algG and algX form part of the previously identified algL-A operon. A promoter upstream algA was also detected; however, transcription of algA exclusively from this promoter is not sufficient for the AlgA levels required for alginate production. An algF mutant (AJ34) was constructed by insertion of the Omega-tetracycline cassette in the non-polar orientation. As expected, AJ34 produced unacetylated alginate. Viability of 35day old cysts formed by strain AJ34, but not of those formed by the wild type, was reduced, indicating that acetylation of alginate plays a role in cyst resistance to desiccation.
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Affiliation(s)
- A Vazquez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, 62250 Morelos, Mexico
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