A nutrient-dependent division antagonist is regulated post-translationally by the Clp proteases in Bacillus subtilis

Changes in nutrient availability have dramatic and well-defined impacts on both transcription and translation in bacterial cells. At the same time, the role of post-translational control in adaptation to nutrient-poor environments is poorly understood. Here we report a role for the bacterial Clp proteases in degradation of the division inhibitor UgtP during growth in nutrient-poor medium. Under nutrient-rich conditions, interactions with its substrate UDP-glucose promote interactions between UgtP and the tubulin-like cell division protein FtsZ in Bacillus subtilis, inhibiting maturation of the cytokinetic ring and increasing cell size. In nutrient-poor medium, reductions in UDP-glucose availability favor UgtP oligomerization, sequestering it from FtsZ and allowing division to occur at a smaller cell mass. Intriguingly, in nutrient-poor conditions UgtP levels are reduced [~] 3-fold independent of UDP-glucose, suggesting an additional layer of regulation. B. subtilis cells cultured under different nutrient conditions indicate that UgtP accumulation is controlled through a nutrient-dependent post-translational mechanism dependent on the Clp proteases. Notably, all three B. subtilis Clp chaperones appeared able to target UgtP for degradation during growth in nutrient-poor conditions. Together these findings highlight conditional proteolysis as a mechanism for bacterial adaptation to a rapidly changing nutritional landscape.