GbpA and chiA genes are not uniformly distributed amongst diverse Vibrio cholerae.

Thea G Fennell,Matthew J Dorman,Nicholas R Thomson,Grace A Blackwell

doi:10.1099/mgen.0.000594

Abstract

Members of the bacterial genus Vibrio utilize chitin both as a metabolic substrate and a signal to activate natural competence. Vibrio cholerae is a bacterial enteric pathogen, sub-lineages of which can cause pandemic cholera. However, the chitin metabolic pathway in V. cholerae has been dissected using only a limited number of laboratory strains of this species. Here, we survey the complement of key chitin metabolism genes amongst 195 diverse V. cholerae. We show that the gene encoding GbpA, known to be an important colonization and virulence factor in pandemic isolates, is not ubiquitous amongst V. cholerae. We also identify a putatively novel chitinase, and present experimental evidence in support of its functionality. Our data indicate that the chitin metabolic pathway within V. cholerae is more complex than previously thought, and emphasize the importance of considering genes and functions in the context of a species in its entirety, rather than simply relying on traditional reference strains.

Highlights

The genus Vibrio of marine gammaproteobacteria contains a number of virulent human pathogens, of significant public health concern [1]
The presence and absence of orthologues of each of the principal chitin-b inding proteins and extracellular chitinases [45] known to be encoded by the V. cholerae 7PET reference strain N16961 were identified in a pangenome calculated from 195 V. cholerae genomes, plus three Vibrio species genomes used as an outgroup (Table S1)
We present three major observations: first, that gbpA is not ubiquitous amongst V. cholerae; second, we show that there is additional variability in the chitinase genes harboured by diverse V. cholerae, which show phylogenetic signals in their distribution; third, we present functional evidence that one of these putatively novel genes encodes a protein with chitinase activity

Summary

Introduction

The genus Vibrio of marine gammaproteobacteria contains a number of virulent human pathogens, of significant public health concern [1]. Most notorious of these pathogens is Vibrio cholerae, members of which are the aetiological agent of cholera in humans [2, 3]. Genomic evidence has shown that classical V. cholerae form a discrete phylogenetic lineage from the lineage causing the seventh cholera pandemic, dubbed.

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Conclusion