GENETICS OF INTEGRATION HOST FACTOR GENES FROM S MUTANS

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Streptococcus mutans is a causative agent of dental caries. It's ability to inflict damage is strongly linked to the production of long chain glucose polymers (glucans) which allow the bacteria to successfully colonize the smooth surface of teeth. To synthesize these glucans the bacteria possesses a family of genes that express enzymes called glucosyltransferases. Expression of the glucosyltransferase genes, gtfB, gtfC and gtfD are strongly regulated. The long term goal of this project is to identify elements that regulate their expression and then to subsequently characterize them. The first modulator identified was the global prokaryotic regulator, Integration Host Factor (IHF). IHF's net effect is to repress cloned S. mutans gtf genes as much as 6 fold when expressed in E. coil. IHF is intimately involved in virtually all forms of nucleoid manipulation i.e. replication, recombination and gene expression. In E. coil and other gram negative bacteria, IHF can affect gene expression through either transcriptional regulation through its ability to bind DNA at its cognate binding site. Before a formal analysis of IHF function of gtf expression can be undertaken it will be necessary to demonstrate that the phenotypes observed in E. coli are similar in S. mutans. Thus the first step is to establish the genetics of IHF homologs in S. mutans. This will include the cloning and sequencing of the IHF genes in addition to constructing IHF mutans in S. mutans. No IHF from any gram positive genera has yet been characterized. Once the genes that code for IHF have been cloned, a preliminary set of complementation experiments will be performed to compare E. coli and S. mutans IHF directly. Finally the S. mutans strain constructed to be deficient in IHF can be assessed to determine their ability to express their gtf genes relative to wild type S. mutans.