Spatial specialization of antioxidant defenses dictates predation success in Myxococcus xanthus

Abstract

Redox-based chemical warfare is a primary driver of microbial community assembly. Here, we show that the predatory bacterium Myxococcus xanthus employs a spatial division of labor between two inducible monofunctional catalases, mxKatB and mxKatE, to overcome prey-derived hydrogen peroxide (H2O2). Quantitative transcript analysis revealed distinct regulatory specificities: mxkatB was the dominant transcriptional responder to exogenous H2O2, whereas mxkatE was preferentially induced by UV irradiation. Biochemical analyses demonstrated strict compartmentalization of enzymatic activity. mxKatE functioned intracellularly, consistent with a role in mitigating endogenous genotoxic stress. In contrast, mxKatB, which harbors an N-terminal Sec-dependent signal peptide, was exclusively localized to the extracellular milieu. Targeted gene deletions corroborated these non-redundant physiological roles. {Delta}katE mutant exhibited severe growth defects and heightened sensitivity to UV and H2O2 yet retained full predation proficiency. Conversely, {Delta}katB mutant displayed unaltered vegetative fitness but were severely impaired in prey lysis due to oxidative inactivation of secreted bacteriolytic enzymes. Failure of cross-complementation confirmed that spatial localization, rather than catalytic capacity, dictates enzyme function. Our findings establish that M. xanthus deploys an extracellular catalase shield to protect its exoenzyme arsenal from prey-derived oxidants. This spatial specialization of antioxidant defenses represents a sophisticated strategy that directly determines the outcome of bacterial predation and shapes interspecies interactions within microbial communities. IMPORTANCEPredatory bacteria such as M. xanthus must withstand chemical defenses deployed by their prey. We show that M. xanthus uses a spatially specialized antioxidant system: an extracellular catalase (mxKatB) secreted to shield its lytic enzymes from prey-derived hydrogen peroxide, and an intracellular catalase (mxKatE) that handles endogenous oxidative stress. This division of labor reveals that bacterial antioxidant defenses can be compartmentalized to protect extracellular weaponry rather than the cell itself, adding a new dimension to how spatial organization of stress responses influences the outcome of microbial competition.