A bacterium's ability to thrive in the presence of multiple environmental stressors simultaneously determines its resilience. We showed that activation of the SigBcontrolled general stress response by mild environmental or energy stress provided significant cross-protection to subsequent lethal oxidative, disulfide and nitrosative stress in Bacillus subtilis. SigB activation is mediated via the stressosome and RsbP, the main conduits of environmental and energy stress, respectively. Cells exposed to mild environmental stress while lacking the major stressosome components RsbT or RsbRA were highly sensitive to subsequent oxidative stress, whereas rsbRB, rsbRC, rsbRD, and ytvA null mutants showed a spectrum of sensitivity, confirming their redundant roles and suggesting they could modulate the signals generated by environmental or oxidative stress. By contrast, cells encountering stationary phase stress required RsbP but not RsbT to survive subsequent oxidative stress. Interestingly, optimum cross-protection against nitrosative stress caused by sodium nitropruside required SigB but not the known regulators, RsbT and RsbP, suggesting an additional and as yet uncharacterized route of SigB activation independent of the known regulators. Together, these results provide mechanistic information on how B. subtilis promotes enhanced resistance against lethal oxidative stress during mild environmental and energy stress conditions.

38A bacterium's ability to thrive in the presence of multiple environmental stressors 39 simultaneously determines its resilience. We showed that activation of the SigB-40 controlled general stress response by mild environmental or nutritional stress provided 41 significant cross-protection to subsequent lethal oxidative, disulfide and nitrosative 42 stress exposure. SigB activation is mediated via the stressosome and RsbP, the main 43 conduits of environmental and nutritional stress, respectively. Cells exposed to mild 44 environmental stress while lacking the major stressosome components RsbT or RsbRA 45were highly sensitive to subsequent oxidative stress, whereas rsbRB, rsbRC, rsbRD 46 and ytvA null mutants showed a spectrum of sensitivity, confirming their redundant roles 47 Interestingly, optimum cross-protection against nitrosative stress caused by SNP 53 required SigB but not the known regulators, RsbT and RsbP, suggesting an additional 54and as yet uncharacterized route of SigB activation independent of the known 55 environmental and energy-stress pathways. Together, these results provide a 56 mechanism for how Bacillus subtilis promotes enhanced resistance against lethal 57 oxidative stress during likely physiologically relevant conditions such as mild 58 environmental or nutrient stress. 59 Importance 60The Bacillus subtilis general stress response is a model for gram-positive pathogens 61 because the regulators are conserved, and the Sigma factor, SigB, controls expression 62 of virulence genes in Listeria monocytogenes. We showed that B. subtilis SigB 63 promotes survival to oxidative, disulfide and nitrosative stress through priming or cross-64 protection. Moreover, when cells were exposed to nitrosative stress, priming was SigB 65dependent, yet the known regulators of SigB were not required, suggesting an 66 alternative mode of SigB activation during nitrosative stress. Importantly, we showed the 67 first genetic requirements of stressosome genes, rsbRB and rsbRD, during oxidative 68 stress cross-protection not explained by environmental stress activation, suggesting a 69 role for stressosome proteins during oxidative stress and advancing the role of SigB 70 during antioxidant protection. 71 72 73