Assessment of CcpA-mediated catabolite control of metabolism and enterotoxin production in Bacillus cereus ATCC 14579

In Bacillus cereus the catabolite control protein CcpA was shown to be involved in optimizing the efficiency of glucose catabolism by activating genes encoding glycolytic enzymes including a non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase that mediates conversion of D-glyceraldehyde 3-phosphate to 3-phospho-D-glycerate in one single step, and by repressing genes encoding the citric acid cycle and gluconeogenic enzymes. Two B. cereus-specific CcpA-regulated operons were identified, encoding enzymes involved in the catabolism of fuculose/arabinose and aspartate. In addition, a genome search using the CRE-site consensus predicted the B. cereus CcpA regulon to include 10 PTS-system gene clusters as well as genes coding for overflow metabolic enzymes leading to acetoin and acetate. Notably, catabolite repression of the genes encoding non-hemolytic enterotoxin (Nhe) and hemolytic (Hbl) enterotoxin appeared CcpA-dependent, and for the corresponding enterotoxin operons, putative CRE-sites were identified. This points to metabolic control of enterotoxin gene expression and suggests that CcpA-mediated glucose sensing provides an additional mode of control to PlcR activated expression of nhe and hbl genes in B. cereus.