Abstract
Vibrio vulnificus is a pathogen with a high invasive capability that causes high mortality in infected individuals. In order to solve the problem of the bacterial infection, it is essential to understand its pathogenesis. In bacteria, the detection of environmental signals and thereafter modulation of gene expression are commonly controlled by the two-component regulatory systems (2CS). Certain 2CSs have been shown that they can sense the in vivo environments for pathogenic bacteria and thus the inactivation of them results in a significant reduction in their virulence. In V. vulnificus, there are more than 40 sets of 2CS, but the functional roles of these 2CSs are poorly defined. To address this question, we set up an oligonucleotide array to investigate the expression profiles of V. vulnificus 2CS genes under different environmental stimuli. When V. vulnificus is grown in the presence of superoxide generator paraquat, expression of several response regulator genes such as gltR, phoB, citB, pleD, and lytR were found to be activated 10.6, 31.8, 3.2, 12.3, and 9.8 folds, respectively. Therefore, we chose lytR as a model for further investigation by generating a deletion mutant using the allelic exchange technique. The lytR mutant strain was further confirmed by PCR and Southern blot analysis. Functional analysis showed that the mutant exhibits normal growth rates, colony size, swarming activity, susceptibility to various antimicrobial agents, and adaptive response to environmental changes. The discernible difference is that the lytR mutant displays a faster rate of cell lysis in the presence of 0.05% Triton X-100 comparing to the parental strain. The lytR mutant also shows a decrease in susceptibility to the killing effects of penicillin and a decline in biofilm formation. Furthermore, the use of real time PCR revealed that lrgA is regulated by LytSR under the stress of H2O2.