Expression data of S. mutans in semi synthetic medium with 0.5% sucrose. Streptococcus mutans

The autoinducer-2 (AI-2) group of signalling molecules represent a new type of cell-cell communication since they are produced by many phylogenetic groups of bacteria as the by product of a metabolic transformation carried out by the luxS enzyme. To separate the metabolic function of the luxS enzyme from the signalling role of AI-2, we carried out a global transcriptome analysis of a luxS null mutant of Streptococcus mutans UA159, an important cariogenic bacterium and crucial component of the dental plaque biofilm community. The data revealed fundamental changes in gene expression affecting 585 genes (appr. 30 % of the genome) which could not be restored by chemically synthesized DPD, the precursor of AI-2, and which are therefore related to the metabolic function of the luxS enzyme in the activated methyl cycle. All functional classes of enzymes were affected, including genes known for their pleiotropic effects in S. mutans, consistent with the impaired biofilm formation of the luxS deficient strain which could not be restored by added AI-2. At the same time, 59 genes were found whose transcription clearly responded to the addition of AI-2. Some of them were related to protein synthesis, stress, and cell division and so were probably indirectly controlled by AI-2. However, three density dependent transcriptional regulators were identified which were directly regulated by AI-2, since their transcription was stimulated repeatedly by its addition. Moreover, three specific components of membrane transport systems were upregulated after addition of AI-2, suggesting they might be involved in its uptake. Finally, a global regulatory protein, the δ subunit of the RNA polymerase (rpoE) was induced 147fold by AI-2, representing the largest differential gene expression observed in our analysis. The data show for the first time a signalling role of AI-2 on the cellular level in Gram positive bacteria. Keywords: time course Overall design: S. mutans UA159 wild type was cultured anaerobically in BM medium containing 0.5% sucrose at 37°C, and the samples were collected at the following optical densities of the culture: 0.05, 0.1, 0.2, 0.3, 0.5, 0.7, 0.9 and 1.2. To obtain the same amount of RNA from each growth stage, the volumes of the samples withdrawn ranged from 200 ml (OD600 = 0.05) to 2.5 ml (OD600 = 1.2). The samples were fixed using RNA Protect Bacterial Reagent (Qiagen, Hilden, Germany). For each time point, two biological and two technical replicates were measured. Signal intensities were averaged among the technical replicates. In addition, normalized signal intensities from gene replicates were averaged and transformed into relative signal log2 ratios (SLR), whereby single averaged signal intensities were compared to the average of time 0 group signal intensities. Genes were selected that SLR differed by more than two over the entire time course.