Cyclic di-GMP Increases Catalase Production and Hydrogen Peroxide Tolerance in Vibrio cholerae

Abstract

Vibrio cholerae is a Gram-negative bacterial pathogen that causes the disease cholera, which affects nearly 1 million people each year. In between outbreaks, V. cholerae resides in fresh and salt water environments where it is able to persist through changes in temperature, oxygen, and salinity. One key characteristic that promotes environmental persistence of V. cholerae is the ability to form multicellular communities, called biofilms, that often adhere to biotic and abiotic sources. Biofilm formation in V. cholerae is positively regulated by the dinucleotide second messenger cyclic dimeric guanosine monophosphate (c-di-GMP). While most research on the c-di-GMP regulon has focused on biofilm formation or motility, we hypothesized the c-di-GMP signaling network encompassed a larger set of effector functions than reported. We found that high intracellular c-di-GMP increased catalase activity approximately 4-fold relative to strains with unaltered c-di-GMP. Genetic studies demonstrated that c-di-GMP mediated catalase activity was due to increased expression of the catalase encoding gene katB. Moreover, c-di-GMP mediated regulation of catalase activity and katB expression required the c-di-GMP dependent transcription factors VpsT and VpsR. Lastly, we found that high c-di-GMP increased survival after H2O2 challenge in a katB, vpsR, and vpsT dependent manner. Our results indicate antioxidant production is regulated by c-di-GMP in V. cholerae uncovering a new node in the growing VpsT and VpsR c-di-GMP signaling network. Importance As a result of infection with V. cholerae, patients become dehydrated leading to death if not properly treated. The marine environment is the natural reservoir for V. cholerae where it can survive alterations in temperature, salinity, and oxygen. The second messenger molecule c-di-GMP is an important signal regulating host and marine environmental persistence because it controls whether V. cholerae will form a biofilm or disperse through flagellar motility. In this work, we demonstrate another function of c-di-GMP in V. cholerae biology: promoting tolerance to the reactive oxygen species H2O2 through differential regulation of catalase expression. Our results suggest a mechanism where c-di-GMP simultaneously controls biofilm formation and antioxidant production, which could promote persistence in human and marine environments.