Cellular Adjustments Of Bacillus Subtilis And Other Bacilli To Fluctuating Salinities

The soil-dwelling bacterium Bacillus subtilis inhabits an ecological niche subjected to frequent changes in osmotic and saline conditions that are caused by rainfall and desiccation. Such changes elicit water fluxes across the cytoplasmic membrane and can drive up turgor under hypo-osmotic conditions to such an extent that the cell will rupture, or under hyper-osmotic conditions, cause the dehydration of the cytoplasm, a reduction in turgor and eventually growth arrest and cell death. Proteome and genome-wide transcriptional profiling studies have highlighted the complexity and multifaceted nature of the osmotic stress response systems of B. subtilis. However, it is beyond doubt that effective water management by the cell is the cornerstone of its acclimatization to either sudden or sustained rises in the environmental osmolarity and the osmotic downshift that inevitably will follow hyperosmotic growth conditions. The accumulation and expulsion of ions and compatible solutes play key roles in these cellular osmotic adjustment processes.