Antibiotic Production by Myxobacteria Plays a Role in Predation

Myxobacteria are predatory and are prolific producers of secondary metabolites. Here, we tested a hypothesized role that secondary metabolite antibiotics function as weapons in predation. To test this, aMyxococcus xanthus Δta1 mutant, blocked in antibiotic TA (myxovirescin) production, was constructed. This TA− mutant was defective in producing a zone of inhibition (ZOI) againstEscherichia coli . This shows that TA is the majorM. xanthus -diffusible antibacterial agent againstE. coli . Correspondingly, the TA− mutant was defective inE. coli killing. Separately, an engineeredE. coli strain resistant to TA was shown to be resistant toward predation. Exogenous addition of spectinomycin, a bacteriostatic antibiotic, rescued the predation defect of the TA− mutant. In contrast, againstMicrococcus luteus the TA− mutant exhibited no defect in ZOI or killing. Thus, TA plays a selective role on prey species. To extend these studies to other myxobacteria, the role of antibiotic corallopyronin production in predation was tested and also found to be required forCorallococcus coralloides killing onE. coli . Next, a role of TA production in myxobacterial fitness was assessed by measuring swarm expansion. Here, the TA− mutant had a specific swarm rate reduction on prey lawns, and thus reduced fitness, compared to an isogenic TA+ strain. Based on these observations, we conclude that myxobacterial antibiotic production can function as a predatory weapon. To our knowledge, this is the first report to directly show a link between secondary metabolite production and predation.