Chemical Interrogation Of Sporulation And Cell Division In Streptomyces

Abstract

Cell division is essential for spore formation but not for viability in the filamentous streptomycetes bacteria. Failure to complete cell division instead blocks spore formation, a phenotype that can be visualized by the absence of gray (in Streptomyces coelicolor) and green (in Streptomyces venezuelae) spore-associated pigmentation. The streptomycetes divisome is however, similar to that of other prokaryotes. We hypothesized chemical inhibitors of sporulation in model streptomycetes might interfere with cell division in rod shaped bacteria. To test this, we investigated 196 compounds that inhibit sporulation in Streptomyces coelicolor. We show that 19 of these compounds cause filamentous growth in Bacillus subtilis, consistent with impaired cell division. One of the compounds is a DNA damaging agent and inhibits cell division by activating the SOS response. The remaining 18 act independently of known stress responses and may therefore act on the divisome or on divisome positioning and stability. Three of the compounds (Fil-1, 2 and 3) confer distinct cell division defects on B. subtilis. They also block B. subtilis sporulation, which is mechanistically unrelated to the sporulation pathway of streptomycetes but which is also dependent on the divisome. We discuss ways in which these differing phenotypes can be used in screens for cell division inhibitors. In addition to the molecules affecting the divisome, DNA and cell wall damage also affects the process indirectly by temporarily halting the cell division. To further explore the cell division regulation in stressful conditions, we carried the complete transcriptomic analysis of S. venezuelae after the DNA damage. The observed changes in the gene expression as a result of the DNA damage paves the way for identification of the DNAdamage induced cell division inhibitor in streptomycetes.