Mutation in and Genes of Inversely Involved in -Independent Biofilm Driving Bacterium Toward Nutrients in Lake Water.

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