Identification of a Novel Bacteriocin Regulatory System in Streptococcus mutans

Recently, we described the function of a novel two-gene regulatory system consisting of a LytTR family transcription regulator and a membrane protein, which we referred to as the hdrRM operon. We determined that the HdrRM system controls the expression of another similar regulatory system annotated as SMU.2080 and SMU.2081. Like hdrRM, the SMU.2080 – 2081 operon encodes a LytTR family transcription regulator and membrane protein, which we now refer to as BrsR and BrsM, respectively. In this study, we used microarray to examine the regulatory role of BrsR and found that it functions as a transcription activator for a variety of bacteriocins and bacteriocin-related genes. Streptococcus mutans UA140 derivatives, lacA ( genotype: ΔbrsRM /pFW5::PlacA ) and lacA2080 (genotype:ΔbrsRM /pFW5::PlacA-brsR), were cultivated overnight at 37°C in a chemically-defined medium containing 0.5% (wt/vol) glucose as carbon source . The overnight cultures were diluted 1:30 in CDM with 1% (wt/vol) lactose in a total volume of 30 ml. The cells were allowed to grow to an optical density at 600 nm of 0.3 and RNA was extracted. The transcriptional profile of the whole genome was examined with microarray.