The Role Of CcpA In Listeria Monocytogenes

Listeria monocytogenes is a gram-positive, food-borne facultative intracellular pathogen that causes invasive, life-threatening infections, mainly in pregnant women, newborns, the elderly, and the immunosuppressed. CcpA (catabolite control protein A) coded by ccpA, is a pleiotropic regulator. In low-GC Gram-positive bacteria, CcpA plays a role in various physiological process in addition to Carbon catabolite repression (CCR), including central carbon and nitrogen metabolism, biofilm formation and toxin gene expression.. A ccpA homolog is present in L. monocytogenes. Although the role of CcpA in CCR has been demonstrated, its putative function in cellular physiological process has not been elucidated. Therefore, a ccpA deletion mutant of L. monocytogenes was constructed, and roles of ccpA in colony morphology, flagellar motility, carbon utilization and biofilm formation were ananlyzed and compared between L. monocytogenes wild type EGDe and its isogenic ccpA deletion mutant EGDeAccpA. The results were shown as follows:1. CcpA plays an important role in bacterial colony morphology and flagellar movement. EGDeAccpA had a larger cellular size than EGDe, and displayed a rugose colony morphology in the nutrient-rich liquid BHI medium; EGDeAccpA lose flagellar movement, and could not be observed flagella under the microscope; Disruption of ccpA results in the inability of the mutant to grow on glucose-containing minimal medium but increase its growth rate in LB medium.2. CcpA is important for biofilm formation in L. monocytogenes. EGDeAccpA could not form biofilm, but the wild type strain EGDe can form strong biofilm in BHI. Medium.3. CcpA plays an important role in CCR. The growth of EGDe is very well in BHI, but limited in LB with the maximum biomass OD6oo=0.6. Addition of glucose in LB can promote the maximum biomass of EGDe to OD6oo=2.0. However, the growth of EGDeAccpA in LB is as very well as in BHI and does not be affected by addition of glucose, indicating that deletion of CcpA releases the CCR in EGDe.In summary, CcpA is a pleiotropic regulatoris in L. monocytogenes, involved in various physiological process in addition to CCR, including colony morphology, flagellar movement, and biofilm formation. Future study will foucus on the relationship between CcpA and virulence gene expression.