Growth in a Biofilm Induces a Hyperinfectious Phenotype inVibrio cholerae

Abstract

Biofilm formation plays a multifaceted role in the life cycles of a wide variety of microorganisms. In the case of pathogenic Vibrio cholerae, biofilm formation in its native aquatic habitats is thought to aid in persistence during interepidemic seasons and to enhance infectivity upon oral ingestion. The structure of V. cholerae biofilms has been hypothesized to protect the bacteria during passage through the stomach. Here, we directly test the role of biofilm architecture in the infectivity of V. cholerae by comparing the abilities of intact biofilms, dispersed biofilms, and planktonic cells to colonize the mouse small intestine. Not only were V. cholerae biofilms better able to colonize than planktonic cells, but the structure of the biofilm was also found to be dispensable: intact and dispersed biofilms colonized equally, and both vastly out-colonized planktonic cells. The infectious dose for biofilm-derived V. cholerae was orders of magnitude lower than that of planktonic cells. This biofilm-induced hyperinfectivity may be due in part to a higher growth rate of biofilm-derived cells during infection. These results suggest that the infectious dose of naturally occurring biofilms of V. cholerae may be much lower than previously estimated using cells grown planktonically in vitro. Furthermore, this work implies the existence of factors specifically induced during growth in a biofilm that augment infection by V. cholerae.Bacteria are often found in biofilms, surface-attached aggregates of microorganisms encased in an extracellular polysaccharide or protein matrix (14). Mature bacterial biofilms often assume a three-dimensional structure composed of pillars of bacteria separated by fluid-filled channels (15). Compared to their free-living, planktonic (PL) counterparts, biofilm-associated bacteria have been shown to be recalcitrant to a variety of stresses and antimicrobial agents, including chlorine, low pH, UV irradiation, antibiotics, host defenses, and more (4,16,21,22,39,40,44,63,72). The structure of the biofilm itself has been thought to physically protect the bacteria within. The decreased susceptibility of biofilms to antibiotics, for example, is understood to be due at least in part to decreased permeability of the biofilm to the antibiotic (20,30,60). However, growth rate and metabolic state have also been proposed to contribute to biofilm-related protection from certain antimicrobials and other stresses (5,25,59,68). In addition, distinct genetic mechanisms of antibiotic resistance employed by biofilm microorganisms have been described (34,41,42).The ability to form biofilms is a virulence determinant of many microorganisms. Classic examples of biofilm infections include chronic infections of the cystic fibrosis lung by Pseudomonas aeruginosa, Haemophilus influenzae and Streptococcus pneumoniae in chronic otitis media, uropathogenic Escherichia coli in recurrent urinary tract infections, and disease caused by microbial biofilms on a variety of indwelling medical devices (27,35,36,52,56). The reduced su...

Extracellular matrix structure governs invasion resistance in bacterial biofilms

“…Biofilm production is strongly implicated in V. cholerae disease transmission and environmental survival on biotic and abiotic surfaces (Watnick et al, 2001;Kierek and Watnick, 2003;Matz et al, 2005;Nielsen et al, 2006;Fong et al, 2010;Tamayo et al, 2010). We find that biofilms exclude immotile planktonic cells from gaining access to the interior and from remaining bound to the biofilm surface.…”

A fitness trade-off between local competition and dispersal in Vibrio cholerae biofilms

“…We use the model organism V. cholerae, which generates biofilms on a range of surfaces, including the exoskeletons of marine arthropods and the intestinal tracts of animal and human hosts (21,22). V. cholerae initiates biofilm growth after adhering to surfaces and shedding its flagella.…”

Microbial Surface Colonization and Biofilm Development in Marine Environments

“…QS-mediated biofilm formation can include large numbers of toxigenic V. chol-erae bacteria, usually in the viable-but-nonculturable (VBNC) state (33, 553, 554). Such biofilm-associated V. cholerae bacteria are more virulent than their free-living counterparts (512,553,555,556), and VBNC V. cholerae can be resuscitated by QS autoinducers (557), which also promote horizontal gene transfer to V. cholerae in multispecies biofilms (558). QS-regulated chitin metabolism also enhances the resistance of V. cholerae biofilms against heterotrophic protist grazing (559).…”