Factors contributing to @entity273 resistance in @entity328 include XXXX oxidase (SpxB) and avoidance of the toxic effects of the fenton reaction.

@entity274 @entity68 @entity526 @entity21809 @entity2260 @entity855 @entity273 @entity3787 @entity328 @entity2388
Aerobic growth of @entity328 results in production of amounts of @entity273 ( @entity274 ) that may exceed 1 mM in the surrounding media. @entity274 production by @entity2260 has been shown to kill or inhibit the growth of other respiratory tract flora, as well as to have cytotoxic effects on host cells and tissue. The mechanisms allowing @entity2260 , a catalase-deficient species, to survive endogenously generated concentrations of @entity274 that are sufficient to kill other bacterial species is unknown. In the present study, @entity2388 oxidase (SpxB), the enzyme responsible for endogenous @entity274 production, was required for survival during exposure to high levels (20 mM) of exogenously added @entity274 . Pretreatment with @entity274 did not increase @entity274 resistance in the mutant, suggesting that SpxB activity itself is required, rather than an @entity274 -inducible pathway. SpxB mutants synthesized 85% less @entity21809 , a potential source of @entity855 . During @entity274 exposure, @entity855 levels decreased more rapidly in spxB mutants than in wild-type cells, suggesting that the increased killing of spxB mutants was due to more rapid @entity855 depletion. Together, these data support the hypothesis that @entity2260 SpxB contributes to an @entity274 -resistant energy source that maintains viability during oxidative stress. Thus, SpxB is required for resistance to the toxic by-product of its own activity. Although @entity274 -dependent @entity3787 radical production and the intracellular concentration of free @entity68 were similar to that of @entity526 , killing by @entity274 was unaffected by @entity68 chelators, suggesting that @entity2260 has a novel mechanism to avoid the toxic effects of the Fenton reaction.
