Dataset Information

Systematic genetic dissection of chitin degradation and uptake in Vibrio cholerae.

ABSTRACT: Vibrio cholerae is a natural resident of the aquatic environment, where a common nutrient is the chitinous exoskeletons of microscopic crustaceans. Chitin utilization requires chitinases, which degrade this insoluble polymer into soluble chitin oligosaccharides. These oligosaccharides also serve as an inducing cue for natural transformation in Vibrio species. There are 7 predicted endochitinase-like genes in the V. cholerae genome. Here, we systematically dissect the contribution of each gene to growth on chitin as well as induction of natural transformation. Specifically, we created a strain that lacks all 7 putative chitinases and from this strain, generated a panel of strains where each expresses a single chitinase. We also generated expression plasmids to ectopically express all 7 chitinases in our chitinase deficient strain. Through this analysis, we found that low levels of chitinase activity are sufficient for natural transformation, while growth on insoluble chitin as a sole carbon source requires more robust and concerted chitinase activity. We also assessed the role that the three uptake systems for the chitin degradation products GlcNAc, (GlcNAc)2 and (GlcN)2 , play in chitin utilization and competence induction. Cumulatively, this study provides mechanistic details for how this pathogen utilizes chitin to thrive and evolve in its environmental reservoir.

SUBMITTER: Hayes CA

PROVIDER: S-EPMC5647239 | biostudies-other | 2017 Oct

REPOSITORIES: biostudies-other

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Systematic genetic dissection of chitin degradation and uptake in Vibrio cholerae.

Hayes Chelsea A CA Dalia Triana N TN Dalia Ankur B AB

Environmental microbiology 20170814 10

Vibrio cholerae is a natural resident of the aquatic environment, where a common nutrient is the chitinous exoskeletons of microscopic crustaceans. Chitin utilization requires chitinases, which degrade this insoluble polymer into soluble chitin oligosaccharides. These oligosaccharides also serve as an inducing cue for natural transformation in Vibrio species. There are 7 predicted endochitinase-like genes in the V. cholerae genome. Here, we systematically dissect the contribution of each gene to ...[more]

PMID: 28752963

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Project description:Both fermentative and respiratory processes contribute to bacterial metabolic adaptations to low oxygen tension (hypoxia). In the absence of O2 as a respiratory electron sink, many bacteria utilize alternative electron acceptors, such as nitrate (NO3-). During canonical NO3- respiration, NO3- is reduced in a stepwise manner to N2 by a dedicated set of reductases. Vibrio cholerae, the etiological agent of cholera, requires only a single periplasmic NO3- reductase (NapA) to undergo NO3- respiration, suggesting that the pathogen possesses a noncanonical NO3- respiratory chain. In this study, we used complementary transposon-based screens to identify genetic determinants of general hypoxic growth and NO3- respiration in V. cholerae We found that while the V. cholerae NO3- respiratory chain is primarily composed of homologues of established NO3- respiratory genes, it also includes components previously unlinked to this process, such as the Na+-NADH dehydrogenase Nqr. The ethanol-generating enzyme AdhE was shown to be the principal fermentative branch required during hypoxic growth in V. cholerae Relative to single adhE or napA mutant strains, a V. cholerae strain lacking both genes exhibited severely impaired hypoxic growth in vitro and in vivo Our findings reveal the genetic basis of a specific interaction between disparate energy production pathways that supports pathogen fitness under shifting conditions. Such metabolic specializations in V. cholerae and other pathogens are potential targets for antimicrobial interventions.IMPORTANCE Bacteria reprogram their metabolism in environments with low oxygen levels (hypoxia). Typically, this occurs via regulation of two major, but largely independent, metabolic pathways: fermentation and respiration. In this study, we found that the diarrheal pathogen Vibrio cholerae has a respiratory chain for NO3- that consists largely of components found in other NO3- respiratory systems but also contains several proteins not previously linked to this process. Both AdhE-dependent fermentation and NO3- respiration were required for efficient pathogen growth under both laboratory conditions and in an animal infection model. These observations provide a specific example of fermentative respiratory interactions and identify metabolic vulnerabilities that may be targetable for new antimicrobial agents in V. cholerae and related pathogens.

Dataset Information

Systematic genetic dissection of chitin degradation and uptake in Vibrio cholerae.

Publications

Systematic genetic dissection of chitin degradation and uptake in Vibrio cholerae.

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