AUTHOR=Sinha-Ray Shrestha , Ali Afsar 

TITLE=Mutation in flrA and mshA Genes of Vibrio cholerae Inversely Involved in vps-Independent Biofilm Driving Bacterium Toward Nutrients in Lake Water

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.01770

DOI=10.3389/fmicb.2017.01770

ISSN=1664-302X

ABSTRACT=<p>Many bacterial pathogens promote biofilms that confer resistance against stressful survival conditions. Likewise <italic>Vibrio cholerae</italic> O1, the causative agent of cholera, and ubiquitous in aquatic environments, produces <italic>vps</italic>-dependent biofilm conferring resistance to environmental stressors and predators. Here we show that a 49-bp deletion mutation in the <italic>flrA</italic> gene of <italic>V. cholerae</italic> N16961S strain resulted in promotion of <italic>vps-</italic>independent biofilm in filter sterilized lake water (FSLW), but not in nutrient-rich L-broth. Complementation of <italic>flrA</italic> mutant with the wild-type <italic>flrA</italic> gene inhibited <italic>vps</italic>-independent biofilm formation. Our data demonstrate that mutation in the <italic>flrA</italic> gene positively contributed to <italic>vps</italic>-independent biofilm production in FSLW. Furthermore, inactivation of <italic>mshA</italic> gene, encoding the main pilin of mannose sensitive hemagglutinin (MSHA pilus) in the background of a Δ<italic>flrA</italic> mutant, inhibited <italic>vps-</italic>independent biofilm formation. Complementation of Δ<italic>flrA</italic>Δ<italic>mshA</italic> double mutant with wild-type <italic>mshA</italic> gene restored biofilm formation, suggesting that <italic>mshA</italic> mutation inhibited Δ<italic>flrA</italic>-driven biofilm. Taken together, our data suggest that <italic>V. cholerae flrA</italic> and <italic>mshA</italic> act inversely in promoting <italic>vps</italic>-independent biofilm formation in FSLW. Using a standard chemotactic assay, we demonstrated that <italic>vps</italic>-independent biofilm of <italic>V. cholerae</italic>, in contrast to <italic>vps</italic>-dependent biofilm, promoted bacterial movement toward chitin and phosphate in FSLW. A Δ<italic>flrA</italic>Δ<italic>mshA</italic> double mutant inhibited the bacterium from moving toward nutrients; this phenomenon was reversed with reverted mutants (complemented with wild-type <italic>mshA</italic> gene). Movement to nutrients was blocked by mutation in a key chemotaxis gene, <italic>cheY</italic>-3, although, <italic>cheY</italic>-3 had no effect on <italic>vps</italic>-independent biofilm. We propose that in fresh water reservoirs, <italic>V. cholerae</italic>, on repression of flagella, enhances <italic>vps</italic>-independent biofilm that aids the bacterium in acquiring nutrients, including chitin and phosphate; by doing so, the microorganism enhances its ability to persist under nutrient-limited conditions.</p>