Contributions of Individual σ ^B -Dependent General Stress Genes to Oxidative Stress Resistance of Bacillus subtilis

Abstract

The general stress regulon of Bacillus subtilis comprises approximately 200 genes and is under the control of the alternative sigma factor B . The activation of B occurs in response to multiple physical stress stimuli as well as energy starvation conditions. The expression of the general stress proteins provides growing and stationary nonsporulating vegetative cells with nonspecific and broad stress resistance. A previous comprehensive phenotype screening analysis of 94 general stress gene mutants in response to severe growth-inhibiting stress stimuli, including ethanol, NaCl, heat, and cold, indicated that secondary oxidative stress may be a common component of severe physical stress. Here we tested the individual contributions of the same set of 94 mutants to the development of resistance against exposure to the superoxide-generating agent paraquat and hydrogen peroxide (H 2 O 2 ). In fact, 62 mutants displayed significantly decreased survival rates in response to paraquat and/or H 2 O 2 stress compared to the wild type at a confidence level of an ␣ value of <0.01. Thus, we were able to assign 47 general stress genes to survival against superoxide, 6 genes to protection from H 2 O 2 stress, and 9 genes to the survival against both. Furthermore, we show that a considerable overlap exists between the phenotype clusters previously assumed to be involved in oxidative stress management and the actual group of oxidative-stress-sensitive mutants. Our data provide information that many general stress proteins with still unknown functions are implicated in oxidative stress resistance and further support the notion that different severe physical stress stimuli elicit a common secondary oxidative stress.

Aag Hypoxanthine-DNA Glycosylase Is Synthesized in the Forespore Compartment and Involved in Counteracting the Genotoxic and Mutagenic Effects of Hypoxanthine and Alkylated Bases in DNA during Bacillus subtilis Sporulation

“…In contrast to alkA, B. subtilis aag does not seem to be under the control of the Ada response (43); however, aag expression is regulated in concert with the general stress B regulon (25,26). Furthermore, inducible levels of expression of this gene were detected during spore germination/outgrowth (44).…”

“…Based on these results, we postulate that aag is an additional member of the G regulon. Of note, katX was also reported to be part of the B regulon (25,26), and previous work also demonstrated that F directs katX expression inside the forespore compartment during B. subtilis sporulation (24).…”

“…In the genome of B. subtilis, aag is oriented adjacent to but in the opposite orientation from katX, a gene expressed only in the developing forespore compartment of sporulating cells and encoding a catalase that protects germinating spores against hydrogen peroxide (24). Despite studies reporting induction of aag as part of the general stress response (25,26), inspection of the katX-aag intergenic region does not reveal DNA sequences with obvious homology to vegetative or sporulation promoters that may regulate aag expression. Therefore, the molecular mechanisms involved in regulating the expression of aag during the life cycle of B. subtilis were studied in this work.…”

Role of Bacillus subtilis Error Prevention Oxidized Guanine System in Counteracting Hexavalent Chromium-Promoted Oxidative DNA Damage

“…In B. subtilis, katA is mainly expressed in growing cells, and its transcription can be stimulated by hydrogen peroxide (40). On the other hand, katB transcription takes place during the transition growth phase as part of the B regulon; of note, in addition to heat, ethanol, and hyperosmotic stresses, the expression of this regulon can also be stimulated by oxidative-stress inducers, including hydrogen peroxide (41,59). On the basis of these observations, we can speculate that Cr(VI) promotes oxidative stress in vegetative B. subtilis cells and that such an event activates the PerR and B transcriptional responses to counteract the deleterious effects of the oxyanion.…”

Catalase Activity as a Biomarker for Mild-Stress-Induced Robustness in Bacillus weihenstephanensis

“…Indeed, some studies showed that different severe stresses elicited a common secondary oxidative stress. Severe stresses, including heat and acid stress treatments, caused radical formation in B. cereus (24)(25)(26), and a phenotypic screening of B. subtilis mutants showed that many of the genes displaying multiple severe stress management effects appeared to be involved in protection against oxidative damage (16,27). Also, in B. weihenstephanensis, a secondary oxidative stress response may be a common component of multiple severe stress stimuli, and it is conceivable that pretreatment with mild oxidative stress provides bacterial cells with a better ability to survive these conditions.…”