Flagella-dependent inhibition of biofilm formation by sub-inhibitory concentration of polymyxin B in Vibrio cholerae

Abstract

Biofilm formation is a common strategy used by bacteria in order to survive and persist in the environment. In Vibrio cholerae ( V . cholerae ), a Gram-negative pathogen responsible for the cholera disease, biofilm-like aggregates are important for the pathogenesis and disease transmission. Biofilm formation is initiated by the attachment of the bacteria to a surface, followed by maturation stages involving the formation of a biofilm matrix. In V . cholerae , flagella are essential for the initial step of biofilm formation, allowing the bacteria to swim and to detect a surface. In this study, we explored the effect of polymyxin B (PmB), a cationic bacterial antimicrobial peptide, on biofilm formation in pathogenic V . cholerae strains belonging to the O1 and O139 serotypes. We found that sub-inhibitory concentration of PmB induces a reduction of the biofilm formation by V . cholerae O1 and O139. Experiment on preformed biofilm demonstrated that the biofilm formation inhibition occurs at the initial step of biofilm formation, where the flagella are essential. We further characterize the effect of PmB on V . cholerae flagellation. Our results demonstrate that the flagellin expression is not reduced in presence of sub-inhibitory concentration of PmB. However, a decrease of the abundance of flagellin associated with the bacterial cells together with an increase in the secretome was observed. Electron microscopy observations also suggest that the abundance of aflagellated bacteria increases upon PmB supplementation. Finally, in agreement with the effect on the flagellation, a reduction of the bacterial motility is observed. Altogether, our results suggest that the PmB affect V . cholerae flagella resulting in a decrease of the motility and a compromised ability to form biofilm.

Antimicrobial Peptides: Virulence and Resistance Modulation in Gram-Negative Bacteria

“…This inhibition occurred during the early stage of biofilm formation and was correlated with a reduction in the number of flagellated bacteria. Therefore, besides biofilm formation, V. cholerae motility was also impaired in the presence of PmB [66]. A similar effect of indolicin has been reported on P. aeruginosa motility and biofilm formation and involves PsrA, a positive regulator of the type III secretion system important for virulence [67,68].…”

“…This reduction is accentuated by the combination of polymyxin B with gramicin S, another AMP. We recently demonstrated that a subinhibitory concentration of PmB can inhibit biofilm formation in V. cholerae [66]. This inhibition occurred during the early stage of biofilm formation and was correlated with a reduction in the number of flagellated bacteria.…”

Surviving Reactive Chlorine Stress: Responses of Gram-Negative Bacteria to Hypochlorous Acid

“…Some of these genes are directly involved in biofilm formation. For instance, flagella are known to be essential for cell adhesion in the early stages of biofilm formation [ 169 ]. Then, the upregulation of flagellar structures could induce the formation of robust biofilms, representing a protective strategy against HOCl stress.…”

Antimicrobial Blue Light versus Pathogenic Bacteria: Mechanism, Application in the Food Industry, Hurdle Technologies and Potential Resistance

“…Several bacteria, such as B. cereus and E. coli O157:H7, also form multispecies biofilms to enhance their survival in food-processing lines [ 94 , 95 ]. The formation of biofilms is also dependent on bacterial structures that are responsible for initial surface attachment, such as flagella and/or fimbriae (for example, curli) in L. monocytogenes [ 96 , 97 ], S. Typhimurium [ 98 , 99 ], E. coli O157:H7 [ 100 ] and V. cholerae [ 101 ].…”