Chitinases are important virulence factors in Vibrio for degrading the chitin-rich barrier of shrimp.

Vibrio-induced diseases pose a significant threat to shrimp aquaculture. While the mechanisms underlying Vibrio penetration of shrimp shells and the gastrointestinal tract remain unclear, this study implicates chitinases as critical virulence factors. Despite their inability to utilize chitin or shrimp shells as sole carbon and nitrogen sources, three major shrimp pathogens-V. alginolyticus, V. harveyi, and V. parahaemolyticus-thrive on chitin-supplemented media and efficiently degrade shrimp shells. Ten extracellular chitinases were identified and two clades, ChiA and ChiD, are conserved among three Vibrio, underscoring their critical role in chitin degradation by Vibrio. Furthermore, one or two copies of evolutionarily conserved ChtBD3 are identified, facilitating targeting chitin-rich structures as virulence factors. All chitinase genes rapidly respond to shrimp shell or colloidal chitin, particularly Vpchi90, which exhibited a 33,340.8-fold increase in expression, correlating with enhanced chitinase activity. To further investigate their functional role, rVaChi89 (ChiD) and rVpChi90 (ChiA) was successfully heterologous expressed in Bacillus subtilis, achieving yields of 0.58 and 0.91 U/mL, respectively. In vitro assay confirmed their ability to degrade shrimp shells into GlcNAc and chitooligomers, further supporting their role in host invasion. This study highlights Vibrio chitinases as critical virulence factors and potential drug targets, with implications for chitin waste recycling.