Regulation of fatty acid biosynthesis by the global regulator CcpA and the local regulator FabT in Streptococcus mutans

• Published in: Molecular oral microbiology Vol. 30; no. 2; pp. 128 - 146
• Main Authors: Faustoferri, R.C., Hubbard, C.J., Santiago, B., Buckley, A.A., Seifert, T.B., Quivey Jr, R.G.
• Format: Journal Article
• Language: English
• Published: Denmark Blackwell Publishing Ltd 01-04-2015
• Subjects: acid stress response; Bacterial Proteins - genetics; Base Sequence; Dentistry; fatty acid synthesis; Fatty Acids - biosynthesis; Gene Expression Regulation, Bacterial; Hydrogen-Ion Concentration; Molecular Sequence Data; Multigene Family; Mutation; Promoter Regions, Genetic; Streptococcus mutans; Streptococcus mutans - genetics; Transcription, Genetic; fatty acid synthesis; acid stress response; Streptococcus mutans
• ISSN: 2041-1006; 2041-1014
• DOI: 10.1111/omi.12076

Summary
SMU.1745c, encoding a putative transcriptional regulator of the MarR family, maps to a location proximal to the fab gene cluster in Streptococcus mutans. Deletion of the SMU.1745c (fabTSm) coding region resulted in a membrane fatty acid composition comprised of longer‐chained, unsaturated fatty acids (UFA), compared with the parent strain. Previous reports have indicated a role for FabT in regulation of genes in the fab gene cluster in other organisms, through binding to a palindromic DNA sequence. Consensus FabT motif sequences were identified in S. mutans in the intergenic regions preceding fabM, fabTSm and fabK in the fab gene cluster. Chloramphenicol acetyltransferase (cat) reporter fusions, using the fabM promoter, revealed elevated transcription in a ∆fabTSm background. Transcription of fabTSm was dramatically elevated in cells grown at pH values of 5 and 7 in the ∆ fabTSm background. Transcription of fabTSm was also elevated in a strain carrying a deletion for the carbon catabolite repressor CcpA. Purified FabTSm and CcpA bound to the promoter regions of fabTSm and fabM. Hence, the data indicate that FabTSm acts as a repressor of fabM and fabTSm itself and the global regulator CcpA acts as a repressor for fabTSm.