Upregulation of virulence genes promotes Vibrio cholerae biofilm hyperinfectivity

Abstract

Vibrio cholerae remains a major global health threat, disproportionately impacting parts of the world without adequate infrastructure and sanitation resources. In aquatic environments, V. cholerae exists both as planktonic cells and as biofilms, which are held together by an extracellular matrix. V. cholerae biofilms have been shown to be hyperinfective, but the mechanism of hyperinfectivity is unclear. Here we show that biofilm-grown cells, irrespective of the surfaces on which they are formed, are able to markedly outcompete planktonic-grown cells in the infant mouse. Using an imaging technique designed to render intestinal tissue optically transparent and preserve the spatial integrity of infected intestines, we reveal and compare three-dimensional V. cholerae colonization patterns of planktonic-grown and biofilm-grown cells. Quantitative image analyses show that V. cholerae colonizes mainly the medial portion of the small intestine and that both the abundance and localization patterns of biofilm-grown cells differ from that of planktonic-grown cells. In vitro biofilm-grown cells activate expression of the virulence cascade, including the toxin coregulated pilus (TCP), and are able to acquire the cholera toxin-carrying CTXФ phage. Overall, virulence factor gene expression is also higher in vivo when infected with biofilm-grown cells, and modulation of their regulation is sufficient to cause the biofilm hyperinfectivity phenotype. Together, these results indicate that the altered biogeography of biofilm-grown cells and their enhanced production of virulence factors in the intestine underpin the biofilm hyperinfectivity phenotype.

Impact of a human gut microbe onVibrio choleraehost colonization through biofilm enhancement

“…This raises the possibility that uncharacterized interactions between Vc and other members of the gut microbiota may exacerbate Vc virulence and contribute to increased morbidity. Our study also establishes a plausible mechanism used by Pa , and perhaps other gut microbes, to increase the virulence of Vc through induction of biofilm formation, a physiological state in which Vc is known to increase expression of other virulence factors critical for human infection and disease (32, 33). Vc biofilms have also been demonstrated to deform and even damage tissue-engineered soft epithelia mimicking the mechanics the host tissue (38), suggesting that in vivo -formed biofilm structures could negatively impact host gut physiology.…”

Quantitative image analysis of microbial communities with BiofilmQ

“…V. cholerae biofilms inside the mouse intestines (Fig. 1a ) were grown and imaged using confocal microscopy using the microbial identification after passive clarity technique, as described by Gallego-Hernandez et al 33 .…”

Identification of signaling pathways, matrix-digestion enzymes, and motility components controllingVibrio choleraebiofilm dispersal

“…The model pathogen Vibrio cholerae forms biofilms in its aquatic habitat, biofilm cells are especially virulent in mouse models of cholera disease, and biofilms are thought to be critical for cholera transmission. (10)(11)(12)(13)(14) Studies of V. cholerae biofilms have predominantly focused on matrix overproducing strains that constitutively exist in the biofilm mode and that do not disperse. This research strategy has propelled understanding of V. cholerae biofilm attachment and maturation, revealing that the second messenger cyclic diguanylate (c-di-GMP) is a master regulator of biofilm formation, and that expression of vibrio polysaccharide (vps) biosynthetic genes are required.…”