YwlE and the Regulation of the Oxidative Stress Response in Bacillus Anthracis

Abstract

Bacillus anthracis, the causative agent of anthrax, has two plasmids that give the bacteria the ability to evade the host immune response and make the bacteria lethal. Increasing research has shown that there are virulence factors also on the chromosome that increases the virulence and survivability of the bacteria. Previous screens of randomly generated B. anthracis mutants have identified many mutations in genes that have increased the susceptibility of B. anthracis to hydrogen peroxide. Hydrogen peroxide was used as a screen for the mutations because it is one of many reactive oxygen species, which are chemically active molecules released by the host as an antimicrobial defense. We took one of these mutants with a mutation in the YwlE gene and confirmed YwlE's role in resistance to hydrogen peroxide by creating an independent mutation in the YwlE gene. Following this, we created an expression vector containing the YwlE gene and reinserted it into the DYwlE B. anthracis. Experiments with the YwlE complement showed that once restored, the bacteria were comparable in hydrogen peroxide resistance to the wild-type bacteria. Further, we investigated whether the YwlE insertional mutant shows increased susceptibility compared to the wild type bacteria when treated with other reactive oxygen species. Experiments using bleach showed an increased susceptibility of the YwlE insertional mutant compared to the wild-type. We concluded by testing our YwlE insertional mutant in the in vivo model Galleria mellonella. We observed that there was an increase in worm survival when infected with our YwlE insertional mutant compared to WT B. anthracis. Together, these results show that the YwlE gene does play a role in regulating the oxidative stress response in B. anthracis.