CONTROL OF CELL-SHAPE AND ELONGATION BY THE RODA GENE IN BACILLUS-SUBTILIS

The Escherichia coli rodA and ftsW genes and the spoVE gene of Bacillu s subtilis encode membrane proteins that control peptidoglycan synthes is during cellular elongation, division and sporulation respectively. While rodA and ftsW are essential genes in E. coli, the B. subtilis sp oVE gene is dispensable for growth and is only required for the synthe sis of the spore cortex peptidoglycan. In this work, we report on the characterization of a B. subtilis gene, designated rodA, encoding a ho mologue of E. coli RodA. We found that the growth of a B. subtilis str ain carrying a fusion of rodA to the IPTG-inducible P-spac promoter is inducer dependent. Limiting concentrations of inducer caused the form ation of spherical cells, which eventually lysed. An increase in the l evel of IPTG induced a sphere-to-short rod transition that re-establis hed viability. Higher levels of inducer restored normal cell length. S taining of the septal or polar cap peptidoglycan by a fluorescent lect in was unaffected during growth of the mutant under restrictive condit ions. Our results suggest that rodA functions in maintaining the rod s hape of the cell and that this function is essential for viability. In addition, RodA has an irreplaceable role in the extension of the late ral walls of the cell. Electron microscopy observations support these conclusions. The ultrastructural analysis further suggests that the gr owth arrest that accompanies loss of the rod shape is caused by the ce ll's inability to construct a division septum capable of spanning the enlarged cell. RodA is similar over its entire length to members of a large protein family (SEDS, for shape, elongation, division and sporul ation). Members of the SEDS family are probably present in all eubacte ria that synthesize peptidoglycan as part of their cell envelope.