The Vibrio cholerae Extracellular Chitinase ChiA2 Is Important for Survival and Pathogenesis in the Host Intestine

Abstract

In aquatic environments, Vibrio cholerae colonizes mainly on the chitinous surface of copepods and utilizes chitin as the sole carbon and nitrogen source. Of the two extracellular chitinases essential for chitin utilization, the expression of chiA2 is maximally up-regulated in host intestine. Recent studies indicate that several bacterial chitinases may be involved in host pathogenesis. However, the role of V. cholerae chitinases in host infection is not yet known. In this study, we provide evidence to show that ChiA2 is important for V. cholerae survival in intestine as well as in pathogenesis. We demonstrate that ChiA2 de-glycosylates mucin and releases reducing sugars like GlcNAc and its oligomers. Deglycosylation of mucin corroborated with reduced uptake of alcian blue stain by ChiA2 treated mucin. Next, we show that V. cholerae could utilize mucin as a nutrient source. In comparison to the wild type strain, ΔchiA2 mutant was 60-fold less efficient in growth in mucin supplemented minimal media and was also ∼6-fold less competent to survive when grown in the presence of mucin-secreting human intestinal HT29 epithelial cells. Similar results were also obtained when the strains were infected in mice intestine. Infection with the ΔchiA2 mutant caused ∼50-fold less fluid accumulation in infant mice as well as in rabbit ileal loop compared to the wild type strain. To see if the difference in survival of the ΔchiA2 mutant and wild type V. cholerae was due to reduced adhesion of the mutant, we monitored binding of the strains on HT29 cells. The initial binding of the wild type and mutant strain was similar. Collectively these data suggest that ChiA2 secreted by V. cholerae in the intestine hydrolyzed intestinal mucin to release GlcNAc, and the released sugar is successfully utilized by V. cholerae for growth and survival in the host intestine.

The Spore Coat Protein CotE Facilitates Host Colonization by Clostridium difficile

“…Chitin-binding proteins in bacteria can also function as mucolytic enzymes and therefore we investigated CotE for this trait [ 22 , 23 ]. Using a modified mucin degradation assay [ 24 ], we showed mucin degradation mediated by CotE.…”

Staying Alive: Vibrio cholerae ’s Cycle of Environmental Survival, Transmission, and Dissemination

“…The extracellular chitinase ChiA2 was recently found to promote survival and pathogenesis in the host by allowing V. cholerae to utilize mucin as a nutrient source. ChiA2 was shown to de-glycoslate mucin, resulting in the release of GlcNAc and its oligomers, which can then be utilized for growth and survival in the host (106). This link between environmental and host nutrient acquisition is important in the evolution of V. cholerae to become a successful environmental pathogen, allowing it readily navigate two different systems using similar tools.…”

Comparative genomic analysis of Vibrios yields insights into genes associated with virulence towards C. gigas larvae

“…Genes for chitin binding and degradation are present in almost all Vibrio genomes [50,53] and chitin metabolism is an important and highly conserved feature, with roles in survival with marine hosts [54], nutrient acquisition [55], and conjugation of extracellular DNA [56]. With regard to oyster hosts, chitin is one of several essential components of their shell matrix [57], and chitin synthase is highly expressed in early stages of C. gigas larval development [58], and in hemocytes and the mantle of adults [58,59].…”