Genome Structure of the Genus<i>Azospirillum</i>

Martin-Didonet, Claudia Cristina Garcia; Chubatsu, Leda S.; Souza, Emanuel M.; Kleina, M.; Rego, Fabiane Gomes de Moraes; Rigo, L. U.; Yates, M. G.; Pedrosa, Fábio O.

doi:10.1128/jb.182.14.4113-4116.2000

Cited by 52 publications

(44 citation statements)

References 29 publications

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“…So far, the composite genome of Azospirillum has been described as being relatively stable, at least for A. brasilense: indeed, the PFGE profile after field experiments and several isolation procedures remained unchanged for Sp7 and Sp245 (38). Interestingly, here we showed that modification of genome architecture in Azospirillum species occurs in vitro at high frequency (Ͼ10 Ϫ4 ) during phase variation.…”

Section: Discussionmentioning

confidence: 63%

Phase Variation and Genomic Architecture Changes inAzospirillum

et al. 2006

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The plant growth-promoting rhizobacterium Azospirillum lipoferum 4B generates in vitro at high frequency a stable nonswimming phase variant designated 4V I , which is distinguishable from the wild type by the differential absorption of dyes. The frequency of variants generated by a recA mutant of A. lipoferum 4B was increased up to 10-fold. The pleiotropic modifications characteristic of the phase variant are well documented, but the molecular processes involved are unknown. Here, the objective was to assess whether genomic rearrangements take place during phase variation of strain 4B. The random amplified polymorphic DNA (RAPD) profiles of strains 4B and 4V I differed. RAPD fragments observed only with the wild type were cloned, and three cosmids carrying the corresponding fragments were isolated. The three cosmids hybridized with a 750-kb plasmid and pulse-field gel electrophoresis analysis revealed that this replicon was missing in the 4V I genome. The same rearrangements took place during phase variation of 4BrecA. Large-scale genomic rearrangements during phase variation were demonstrated for two additional strains. In Azospirillum brasilense WN1, generation of stable variants was correlated with the disappearance of a replicon of 260 kb. For Azospirillum irakense KBC1, the variant was not stable and coincided with the formation of a new replicon, whereas the revertant recovered the parental genomic architecture. This study shows large-scale genomic rearrangements in Azospirillum strains and correlates them with phase variation.

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Section: Discussionmentioning

confidence: 63%

Phase Variation and Genomic Architecture Changes inAzospirillum

et al. 2006

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“…None of the other Azospirillum species strains sequenced to date shows evidence of a similar domain insertion (34)(35)(36)(37)(38)(39). In fact, the draft genome of an Sp7 strain generated by a team of South Korean scientists also lacks the TMX fusion to CheA1 (NCBI BioProject PRJNA293508).…”

Section: Discussionmentioning

confidence: 99%

“…In fact, the draft genome of an Sp7 strain generated by a team of South Korean scientists also lacks the TMX fusion to CheA1 (NCBI BioProject PRJNA293508). A. brasilense genomes are organized as 7 replicons: one chromosome and 6 large plasmids named p1 through p6 (34)(35)(36)(37)(38)(39). The DNA regions coding for CheA1 and for TMX are both located on the largest plasmid, p1, in all A. brasilense strains with available genome sequences, but they are not adjacent and are separated by several kilobases, precluding a simple frameshifting or slippage mutation between adjacent genes.…”

Section: Discussionmentioning

confidence: 99%

Distinct Domains of CheA Confer Unique Functions in Chemotaxis and Cell Length in Azospirillum brasilense Sp7

2017

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Chemotaxis is the movement of cells in response to gradients of diverse chemical cues. Motile bacteria utilize a conserved chemotaxis signal transduction system to bias their motility and navigate through a gradient. A central regulator of chemotaxis is the histidine kinase CheA. This cytoplasmic protein interacts with membrane-bound receptors, which assemble into large polar arrays, to propagate the signal. In the alphaproteobacterium Azospirillum brasilense, Che1 controls transient increases in swimming speed during chemotaxis, but it also biases the cell length at division. However, the exact underlying molecular mechanisms for Che1-dependent control of multiple cellular behaviors are not known. Here, we identify specific domains of the CheA1 histidine kinase implicated in modulating each of these functions. We show that CheA1 is produced in two isoforms: a membraneanchored isoform produced as a fusion with a conserved seven-transmembrane domain of unknown function (TMX) at the N terminus and a soluble isoform similar to prototypical CheA. Site-directed and deletion mutagenesis combined with behavioral assays confirm the role of CheA1 in chemotaxis and implicate the TMX domain in mediating changes in cell length. Fluorescence microscopy further reveals that the membrane-anchored isoform is distributed around the cell surface while the soluble isoform localizes at the cell poles. Together, the data provide a mechanism for the role of Che1 in controlling multiple unrelated cellular behaviors via acquisition of a new domain in CheA1 and production of distinct functional isoforms.IMPORTANCE Chemotaxis provides a significant competitive advantage to bacteria in the environment, and this function has been transferred laterally multiple times, with evidence of functional divergence in different genomic contexts. The molecular principles that underlie functional diversification of chemotaxis in various genomic contexts are unknown. Here, we provide a molecular mechanism by which a single CheA protein controls two unrelated functions: chemotaxis and cell length. Acquisition of this multifunctionality is seemingly a recent evolutionary event. The findings illustrate a mechanism by which chemotaxis function may be co-opted to regulate additional cellular functions.

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“…The role of GlnZ in the reactivation of dinitrogenase reductase under ammoniumlimiting conditions as well as the requirement of the PII protein to turn the enzyme off were also important to understanding the control of nitrogenase activity in A. brasilense ). In addition, the group determined the genomic structure using pulse-field eletrophoresis of the Azospirillum genus (Martin-Didonet et al 2000) and also constructed gene fusions using gfp and gusA reporter genes to monitor the plant/bacteria interaction (Ramos et al 2002).…”

Section: Genetics Studiesmentioning

confidence: 99%

History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience

Baldani

2005

An. Acad. Bras. Ciênc.

233

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This review covers the history on Biological Nitrogen Fixation (BNF) in Graminaceous plants grown in Brazil, and describes research progress made over the last 40 years, most of which was coordinated by Johanna Döbereiner. One notable accomplishment during this period was the discovery of several nitrogen-fixing bacteria such as the rhizospheric (Beijerinckia fluminensis and Azotobacter paspali), associative (Azospirillum lipoferum, A. brasilense, A. amazonense) and the endophytic (Herbaspirillum seropedicae, H. rubrisubalbicans, Gluconacetobacter diazotrophicus, Burkholderia brasilensis and B. tropica). The role of these diazotrophs in association with grasses, mainly with cereal plants, has been studied and a lot of progress has been achieved in the ecological, physiological, biochemical, and genetic aspects. The mechanisms of colonization and infection of the plant tissues are better understood, and the BNF contribution to the soil/plant system has been determined. Inoculation studies with diazotrophs showed that endophytic bacteria have a much higher BNF contribution potential than associative diazotrophs. In addition, it was found that the plant genotype influences the plant/bacteria association. Recent data suggest that more studies should be conducted on the endophytic association to strengthen the BNF potential. The ongoing genome sequencing programs: RIOGENE (Gluconacetobacter diazotrophicus) and GENOPAR (Herbaspirillum seropedicae) reflect the commitment to the BNF study in Brazil and should allow the country to continue in the forefront of research related to the BNF process in Graminaceous plants.

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Genome Structure of the GenusAzospirillum

Cited by 52 publications

References 29 publications

Phase Variation and Genomic Architecture Changes inAzospirillum

Phase Variation and Genomic Architecture Changes inAzospirillum

Distinct Domains of CheA Confer Unique Functions in Chemotaxis and Cell Length in Azospirillum brasilense Sp7

History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience

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