A New Physiological Role for CcpA in Adaptation of Bacillus Subtilis to Sugar-Induced Osmotic Stress

The model Gram-positive bacterium Bacillus subtilis is liable to be exposed to high-salinity environments in its natural habitats and is often used in fermentation with high concentrations of glucose or other sugars. High salinity or high concentrations of sugars can cause osmotic stress to B. subtilis. Past researches regarding osmoadaptation of B. subtilis were mainly focused on responses to salt-induced osmotic stress. There was little or no mention about how B. subtilis cells responded to sugar-induced osmotic stress. The catabolite control protein (CcpA) is known to be a global transcriptional regulator that mediates glucose repression of many catabolic genes and activation of genes involved in excretion of excess carbon in various Bacillus species. However, the physiological significance for CcpA-mediated sugar activation of degU, gltAB, opuA, opuE, proHJ and the ilvB operon remained poorly defined. Here based on the results from the literature search, it is now proposed that CcpA-mediated sugar activation of these osmoadaptive genes may facilitate the adaptation of B. subtilis to sugar-induced osmotic stress. This finding could add a new physiological role to CcpA in B. subtilis and probably its close relatives. As to biotechnological application, construction of B. subtilis strains that could over-express CcpA might potentially enhance their abilities to withstand higher concentrations of sugars for producing higher yields of various economically effective fermentation products.