The EIIAB^ManPhosphotransferase System Permease Regulates Carbohydrate Catabolite Repression inStreptococcus gordonii

Abstract

Commensal oral streptococci play critical roles in oral biofilm formation and promote dental health by competing with, and antagonizing the growth of, pathogenic organisms, such as Streptococcus mutans. Efficient utilization of the spectrum of carbohydrates in the oral cavity by commensal streptococci is essential for their persistence, and yet very little is known about the regulation of carbohydrate catabolism by these organisms. Carbohydrate catabolite repression (CCR) in the abundant oral commensal Streptococcus gordonii strain DL-1 was investigated using the exo-␤-D-fructosidase gene (fruA) and a fructose/mannose sugar:phosphotransferase (PTS) enzyme II operon (levDEFG) as model systems. Functional studies confirmed the predicted roles of FruA and LevD in S. gordonii. ManL, the AB domain of a fructose/mannose-type enzyme II PTS permease, contributed to utilization of glucose, mannose, galactose, and fructose and exerted primary control over CCR of the fruA and levD operons. Unlike in S. mutans, ManL-dependent CCR was not sugar specific, and galactose was very effective at eliciting CCR in S. gordonii. Inactivation of the apparent ccpA homologue of S. gordonii actually enhanced CCR of fruA and levD, an effect likely due to its demonstrated role in repression of manL expression. Thus, there are some similarities and fundamental differences in CCR control mechanisms between the oral pathogen S. mutans and the oral commensal S. gordonii that may eventually be exploited to enhance the competitiveness of health-associated commensals in oral biofilms.

CcpA-Dependent Carbohydrate Catabolite Repression Regulates Galactose Metabolism in Streptococcus oligofermentans

“…CcpA, the catabolite control protein, is believed to play a key role in CCR regulation in Gram-positive bacteria (8,15,17), whereas ManL, the glucose/mannose PTS permease, is also reported to be involved in CCR in S. mutans and S. gordonii (1,40,46,47). To further understand the regulatory mechanism of CCR in S. oligofermentans, we searched for ccpA homologs in the draft genome of S. oligofermentans using the S. cristatus ccpA gene (ZP_08059449.1) as a query and found a putative ccpA gene (ORF 247).…”

“…It has been reported that CcpA negatively regulates manL in other streptococci (40,46). We determined the manL gene expression in the wild-type strain of S. oligofermentans and the ccpA mutant using both qPCR and a luciferase reporter, which was constructed by fusion of the luc gene to the promoter of the manL gene.…”

“…3A); thus, other galactose transporters might exist in S. oligofermentans. One candidate is the glucose/mannose-specific PTS EIIABC complex encoded by manLMN, which has been shown to be a galactose transporter in S. mutans and S. gordonii (1,40,(46)(47)(48). We searched for the manL homolog in the draft genome of S. oligofermentans using the manL gene (SGO_1679) of S. gordonii as a query.…”

“…In most lactic acid bacteria, the lac operon encodes enzymes for lactose metabolism through the tagatose-6-phosphate pathway, in which the lactosespecific PTS enzyme II (EII Lac ) is responsible for lactose transport via the PTS system (29,41). In oral streptococci, e.g., S. mutans and S. gordonii, transport of galactose is via EII Lac and mannosespecific PTS permease (EII Man ) (40,48). Although genes in the gal operon of S. oligofermentans are homologous to genes of the lac operon in other streptococci (Fig.…”

Interaction with Enzyme IIBMpo(EIIBMpo) and Phosphorylation by Phosphorylated EIIBMpoExert Antagonistic Effects on the Transcriptional Activator ManR of Listeria monocytogenes

“…Glucose is one of the carbohydrates that strongly represses virulence gene expression in L. monocytogenes (17,26). In addition, components of the glucose-transporting PTS Glc in enterobacteriaceae (56) and the PTS Man in firmicutes (57) are involved in the general carbon catabolite repression mechanism. PTS Man components were therefore suggested to function as general virulence gene regulators in L. monocytogenes.…”