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Cellobiose-mediated gene expression in Streptococcus pneumoniae: a repressor function of the novel GntR-type regulator BguR.

Shafeeq S, Kuipers OP, Kloosterman TG - PLoS ONE (2013)

Bottom Line: Its expression was increased in the presence of cellobiose, and decreased in the presence of glucose.A novel GntR-type transcriptional regulator (which we here denote as BguR) was shown to act as a transcriptional repressor of the bgu operon and its repressive effect was relieved in the presence of cellobiose.BguR-dependent repression was demonstrated to be mediated by a 20-bp DNA operator site (5'-AAAAATGTCTAGACAAATTT-3') present in PbguA, as verified by promoter truncation experiments.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands.

ABSTRACT
The human pathogen Streptococcus pneumoniae has the ability to use the carbon- and energy source cellobiose due to the presence of a cellobiose-utilizing gene cluster (cel locus) in its genome. This system is regulated by the cellobiose-dependent transcriptional activator CelR, which has been previously shown to contribute to pneumococcal virulence. To get a broader understanding of the response of S. pneumoniae to cellobiose, we compared the pneumococcal transcriptome during growth on glucose as the main carbon source to that with cellobiose as the main carbon source. The expression of various carbon metabolic genes was altered, including a PTS operon (which we here denote as the bgu operon) that has high similarity with the cel locus. In contrast to the cel locus, the bgu operon is conserved in all sequenced strains of S. pneumoniae, indicating an important physiological function in the lifestyle of pneumococci. We next characterized the transcriptional regulation of the bgu operon in more detail. Its expression was increased in the presence of cellobiose, and decreased in the presence of glucose. A novel GntR-type transcriptional regulator (which we here denote as BguR) was shown to act as a transcriptional repressor of the bgu operon and its repressive effect was relieved in the presence of cellobiose. BguR-dependent repression was demonstrated to be mediated by a 20-bp DNA operator site (5'-AAAAATGTCTAGACAAATTT-3') present in PbguA, as verified by promoter truncation experiments. In conclusion, we have identified a new cellobiose-responsive PTS operon, together with its transcriptional regulator in S. pneumoniae.

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Related in: MedlinePlus

Growth of S. pneumoniae D39 in the presence of 0.5% cellobiose (grey line ▪) and 0.5% glucose (black line ♦) in M17 medium.Black circles show the time points at which cultures were harvested for transcriptome analysis. Where C = cellobiose, G = Glucose, T1 = time point 1 and T2 = Time point 2.
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pone-0057586-g001: Growth of S. pneumoniae D39 in the presence of 0.5% cellobiose (grey line ▪) and 0.5% glucose (black line ♦) in M17 medium.Black circles show the time points at which cultures were harvested for transcriptome analysis. Where C = cellobiose, G = Glucose, T1 = time point 1 and T2 = Time point 2.

Mentions: For transcriptome analyses of S. pneumoniae, the D39 wild-type strain was grown in 3 biological replicates in CM17 (0.5% Cellobiose+M17) and compared to the strain grown in GM17 (0.5% Glucose+M17) medium. Cells were harvested for RNA isolation at two time points in CM17 (CT-1 and CT2) and GM17 (GT-1 and GT-2) medium (see Fig. 1). To analyze the effect of bguR deletion on the transcriptome, S. pneumoniae D39 wild-type and its isogenic bguR mutant (SS300) were grown in 3 biological replicates in GM17 (0.5% Glucose+M17) medium. These cultures were harvested at the mid-exponential phase of growth at an OD600 of 0.25. All other procedures regarding the DNA microarray experiments (cell disruption, RNA isolation, RNA quality testing, cDNA synthesis, labeling with dyes (Cy3 and Cy5), hybridization and scanning) were performed as described before [27], [28].


Cellobiose-mediated gene expression in Streptococcus pneumoniae: a repressor function of the novel GntR-type regulator BguR.

Shafeeq S, Kuipers OP, Kloosterman TG - PLoS ONE (2013)

Growth of S. pneumoniae D39 in the presence of 0.5% cellobiose (grey line ▪) and 0.5% glucose (black line ♦) in M17 medium.Black circles show the time points at which cultures were harvested for transcriptome analysis. Where C = cellobiose, G = Glucose, T1 = time point 1 and T2 = Time point 2.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585215&req=5

pone-0057586-g001: Growth of S. pneumoniae D39 in the presence of 0.5% cellobiose (grey line ▪) and 0.5% glucose (black line ♦) in M17 medium.Black circles show the time points at which cultures were harvested for transcriptome analysis. Where C = cellobiose, G = Glucose, T1 = time point 1 and T2 = Time point 2.
Mentions: For transcriptome analyses of S. pneumoniae, the D39 wild-type strain was grown in 3 biological replicates in CM17 (0.5% Cellobiose+M17) and compared to the strain grown in GM17 (0.5% Glucose+M17) medium. Cells were harvested for RNA isolation at two time points in CM17 (CT-1 and CT2) and GM17 (GT-1 and GT-2) medium (see Fig. 1). To analyze the effect of bguR deletion on the transcriptome, S. pneumoniae D39 wild-type and its isogenic bguR mutant (SS300) were grown in 3 biological replicates in GM17 (0.5% Glucose+M17) medium. These cultures were harvested at the mid-exponential phase of growth at an OD600 of 0.25. All other procedures regarding the DNA microarray experiments (cell disruption, RNA isolation, RNA quality testing, cDNA synthesis, labeling with dyes (Cy3 and Cy5), hybridization and scanning) were performed as described before [27], [28].

Bottom Line: Its expression was increased in the presence of cellobiose, and decreased in the presence of glucose.A novel GntR-type transcriptional regulator (which we here denote as BguR) was shown to act as a transcriptional repressor of the bgu operon and its repressive effect was relieved in the presence of cellobiose.BguR-dependent repression was demonstrated to be mediated by a 20-bp DNA operator site (5'-AAAAATGTCTAGACAAATTT-3') present in PbguA, as verified by promoter truncation experiments.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands.

ABSTRACT
The human pathogen Streptococcus pneumoniae has the ability to use the carbon- and energy source cellobiose due to the presence of a cellobiose-utilizing gene cluster (cel locus) in its genome. This system is regulated by the cellobiose-dependent transcriptional activator CelR, which has been previously shown to contribute to pneumococcal virulence. To get a broader understanding of the response of S. pneumoniae to cellobiose, we compared the pneumococcal transcriptome during growth on glucose as the main carbon source to that with cellobiose as the main carbon source. The expression of various carbon metabolic genes was altered, including a PTS operon (which we here denote as the bgu operon) that has high similarity with the cel locus. In contrast to the cel locus, the bgu operon is conserved in all sequenced strains of S. pneumoniae, indicating an important physiological function in the lifestyle of pneumococci. We next characterized the transcriptional regulation of the bgu operon in more detail. Its expression was increased in the presence of cellobiose, and decreased in the presence of glucose. A novel GntR-type transcriptional regulator (which we here denote as BguR) was shown to act as a transcriptional repressor of the bgu operon and its repressive effect was relieved in the presence of cellobiose. BguR-dependent repression was demonstrated to be mediated by a 20-bp DNA operator site (5'-AAAAATGTCTAGACAAATTT-3') present in PbguA, as verified by promoter truncation experiments. In conclusion, we have identified a new cellobiose-responsive PTS operon, together with its transcriptional regulator in S. pneumoniae.

Show MeSH
Related in: MedlinePlus