Abstract
To persist within the host and cause disease,
relies on its ability to precisely fine-tune virulence factor expression in response to rapidly changing environments. During an unbiased transposon mutant screen, we observed that disruption of a two-gene operon,
, resulted in decreased levels of pigmentation and aureolysin (Aur) activity relative to the wild-type strain. Further analyses revealed that YjbH, a predicted thioredoxin-like oxidoreductase, is predominantly responsible for the observed
mutant phenotypes, though a minor role exists for the putative truncated hemoglobin YjbI. These differences were due to significantly decreased expression of
and
Previous studies found that YjbH targets the disulfide- and oxidative stress-responsive regulator Spx for degradation by ClpXP. The absence of
or
resulted in altered sensitivities to nitrosative and oxidative stress and iron deprivation. Additionally, aconitase activity was altered in the
and
mutant strains. Decreased levels of pigmentation and aureolysin (Aur) activity in the
mutant were found to be Spx dependent. Lastly, we used a murine sepsis model to determine the effect of the
deletion on pathogenesis and found that the mutant was better able to colonize the kidneys and spleens during an acute infection than the wild-type strain. These studies identified changes in pigmentation and protease activity in response to YjbIH and are the first to have shown a role for these proteins during infection.