SummaryIn ever-changing natural environments, bacteria are continuously challenged with numerous biotic and abiotic stresses. Accordingly, they have evolved both specific and more general mechanisms to counteract stress-induced damage and ensure survival. In the soil habitat of Bacillus subtilis, peptide antibiotics and bacteriophages are among the primary stressors that affect the integrity of the cytoplasmic membrane. Dynamin-like proteins (DLPs) play a major role in eukaryotic membrane re-modelling processes, including antiviral activities, but the function of the corresponding bacterial homologues was so far poorly understood. Here, we report on the protective function of a bacterial DLP, DynA from B. subtilis. We provide evidence that DynA plays an important role in a membrane surveillance system that counteracts membrane pore formation provoked by antibiotics and phages. In unstressed cells, DynA is a highly dynamic membrane-associated protein. Upon membrane damage, DynA localizes into large and static assemblies, where DynA acts locally to counteract stress-induced pores, presumably by inducing lipid bilayer fusion and sealing membrane gaps. Thus, lack of DynA increases the sensitivity to antibiotic exposure and phage infection. Taken together, our work suggests that DynA, and potentially other bacterial DLPs, contribute to the innate immunity of bacteria against membrane stress.

Membrane dynamics are involved in crucial processes in eukaryotic and prokaryotic cells. Membrane fusion and fission events are often catalyzed by proteins that belong to the dynamin family of large GTPases. It has recently been shown that members of the dynamin superfamily are also present in many bacterial species. Although structural information about full length bacterial dynamin-like proteins is available, their molecular role remains unclear. We have shown previously that DynA, a dynamin-like protein found in the firmicute Bacillus subtilis is able to fuse membranes in vitro. In contrast to other members of the dynamin family this membrane remodeling activity was not dependent on guanosine nucleotides, but required magnesium. DynA assemblies localize in foci that are often enriched at sites of septation and hence a potential role during bacterial cytokinesis was discussed. In order to identify potential interaction partners we constructed a bacterial-two hybrid (B2H) library and screened for DynA interacting proteins. Three potential interaction partner have been identified, YneK, RNaseY (YmdA), and YwpG. Localization of these proteins phenocopies that of DynA, supporting the potential interaction in vivo.