Cell division and its regulation are essential for survival of bacteria. Despite the fact that many division proteins are conserved in bacterial pathogens, making them attractive as antibacterial targets, there are currently no antibiotics that target cell division or its regulation.
In this study, we applied a differential display proteomic approach, using the model gram positive organism Bacillus subtilis to identify new cell division regulators as potential antibacterial targets. Out of 900 protein spots, we identified 20 proteins that were up- or down-regulated in two populations of B. subtilis that differed only in their ability to regulate division. These proteins were ranked for their potential as antibacterial targets, and genes encoding the top seven proteins were conditionally knocked out in B. subtilis. All deletions resulted in phenotypes suggestive of a role in cell division regulation. However, no gene was essential for the growth of B. subtilis.
Subsequently, the genes encoding putative antibacterial targets were analysed in Staphylococcus aureus. The validation included the generation of temperature-sensitive disruption mutants in the strains S. aureus RN4220 and S. aureus MW2 as an initial screen for essentiality. In contrast to the results obtained with B. subtilis, at least one of the disruption mutants did not grow at the non-permissive temperature, suggesting that the gene is essential for the growth of S. aureus. Disruption of the other genes in S. aureus led to cells that displayed reduced viability. The cells of these disruption mutants had pronounced growth defects, and, or were significant larger in diameter.
We are currently establishing infection models to test whether any of the target genes is essential for infection by S. aureus. Moreover, we will develop assays for screening chemical libraries for inhibitors of these potential targets as an initial step towards developing an antibacterial with a novel mode of action.