The response regulator ComE in Streptococcus mutans functions both as a transcription activator of mutacin production and repressor of CSP biosynthesis (original) (raw)
Related papers
2011
The oral biofilm organism Streptococcus mutans must face numerous environmental stresses to survive in its natural habitat. Under specific stresses, S. mutans expresses the competence-stimulating peptide (CSP) pheromone known to induce autolysis and facilitate the uptake and incorporation of exogenous DNA, a process called DNA transformation. We have previously demonstrated that the CSP-induced CipB bacteriocin (mutacin V) is a major factor involved in both cellular processes. Our objective in this work was to characterize the role of CipB bacteriocin during DNA transformation. Although other bacteriocin mutants were impaired in their ability to acquire DNA under CSP-induced conditions, the ⌬cipB mutant was the only mutant showing a sharp decrease in transformation efficiency. The autolysis function of CipB bacteriocin does not participate in the DNA transformation process, as factors released via lysis of a subpopulation of cells did not contribute to the development of genetic competence in the surviving population. Moreover, CipB does not seem to participate in membrane depolarization to assist passage of DNA. Microarray-based expression profiling showed that under CSP-induced conditions, CipB regulated ϳ130 genes, among which are the comDE locus and comR and comX genes, encoding critical factors that influence competency development in S. mutans. We also discovered that the CipI protein conferring immunity to CipB-induced autolysis also prevented the transcriptional regulatory activity of CipB. Our data suggest that besides its role in cell lysis, the S. mutans CipB bacteriocin also functions as a peptide regulator for the transcriptional control of the competence regulon.
Journal of Bacteriology, 2010
The Streptococcus mutans hdrRM operon encodes a novel two-gene regulatory system induced by high cell density. Previous studies identified hdrM as the only known negative regulator of competence development in S. mutans. In the present study, we demonstrated that the HdrRM system bypasses the prototypical competence gene regulators ComC and ComDE in the transcriptional regulation of the competence-specific sigma factor comX and the late competence genes. Similarly, the HdrRM system can abrogate the requirement for ComE to produce the bacteriocin mutacin IV. To further probe the regulatory mechanism of hdrRM, we created an hdrR overexpression strain and showed that it could reproduce each of the hdrM competence and mutacin phenotypes, indicating that HdrM acts as a negative regulator of HdrR activity. Using a mutacin IV-luciferase reporter, we also demonstrated that the hdrRM system utilizes the same promoter elements recognized by ComE and thus appears to comprise a novel regulatory pathway parallel to ComCDE.
FEMS microbiology …, 2007
The genetic variability in comC, the gene encoding the quorum-sensing molecule, competence-stimulating peptide (CSP) in Streptococcus mutans is reported. Seven comC alleles encoding three distinct mature CSPs were identified among 36 geographically diverse strains, although, compared with Streptococcus pneumoniae, the amount of predicted amino acid sequence variation is low. In agreement with other studies, significant variation was found in the natural competence for DNA uptake in these strains. However, there was no correlation between the CSP genotype and the ability to transform these strains. Representative strains encoding each of the CSP variants became competent in response to synthetic CSPs of each type. Therefore, in contrast to S. pneumoniae, comC alleles in S. mutans are functionally equivalent and there is no evidence of pherotype specificity.
FEMS Microbiology Letters, 2000
Streptococcus mutans is a major cariogenic inhabitant of the high cell density oral biofilm (dental plaque). In previous studies, we showed that production of one of its virulence factors, the bacteriocin mutacin IV, was regulated by high cell density as well as the competence regulatory system ComED. In this study, we utilized luciferase fusions and real-time reverse transcriptase polymerase chain reaction (RT-PCR), to demonstrate that high cell density and ComED also regulate an uncharacterized group of mutacin and mutacin-like genes. Under high cell density or in the presence of externally added competence-stimulating peptide (CSP), gene expression increased 10-to 30-fold. Interestingly, high cell density was able to bypass the requirement for CSP addition. However, both cell density and CSPdependent gene expression had a strict requirement for the ComE response regulator.
Fems Microbiology Letters, 2006
Streptococcus mutans is a major cariogenic inhabitant of the high cell density oral biofilm (dental plaque). In previous studies, we showed that production of one of its virulence factors, the bacteriocin mutacin IV, was regulated by high cell density as well as the competence regulatory system ComED. In this study, we utilized luciferase fusions and real-time reverse transcriptase polymerase chain reaction (RT-PCR), to demonstrate that high cell density and ComED also regulate an uncharacterized group of mutacin and mutacin-like genes. Under high cell density or in the presence of externally added competence-stimulating peptide (CSP), gene expression increased 10- to 30-fold. Interestingly, high cell density was able to bypass the requirement for CSP addition. However, both cell density and CSP-dependent gene expression had a strict requirement for the ComE response regulator.
Journal of Bacteriology, 2011
Competence-stimulating-peptide (CSP)-mediated competence development in Streptococcus mutans is a transient and biphasic process, since only a subpopulation induces the expression of ComX in the presence of CSP, and the activation of the DNA uptake machinery in this fraction shuts down ∼3 to 4 h postinduction. Here, we combine for the first time, to our knowledge, the bacterial flow-cytometric sorting of cells and subpopulation-specific transcriptome analysis of both the competent and noncompetent fraction of CSP-treated S. mutans cells. Sorting was guided by a ComX-green fluorescent protein (ComX-GFP) reporter, and the transcriptome analysis demonstrated the successful combination of both methods, because a strong enrichment of transcripts for comX and its downstream genes was achieved. Three two-component systems were expressed in the competent fraction, and among them was ComDE. Moreover, the recently identified regulator system ComR/S was expressed exclusively in the competent f...
Molecular microbiology, 2005
It is important to ensure DNA availability when bacterial cells develop competence. Previous studies in Streptococcus pneumoniae demonstrated that the competence-stimulating peptide (CSP) induced autolysin production and cell lysis of its own non-competent cells, suggesting a possible active mechanism to secure a homologous DNA pool for uptake and recombination. In this study, we found that in Streptococcus mutans CSP induced co-ordinated expression of competence and mutacin production genes. This mutacin (mutacin IV) is a non-lantibiotic bacteriocin which kills closely related Streptococcal species such as S. gordonii. In mixed cultures of S. mutans and S. gordonii harbouring a shuttle plasmid, plasmid DNA transfer from S. gordonii to S. mutans was observed in a CSP and mutacin IV-dependent manner. Further analysis demonstrated an increased DNA release from S. gordonii upon addition of the partially purified mutacin IV extract. On the basis of these findings, we propose that Strept...
Identification of a novel bacteriocin regulatory system in Streptococcus mutans
Molecular Microbiology, 2010
Recently, we described the function of an uncharacterized two-gene regulatory system consisting of a LytTR family transcription regulator and a putative membrane protein, which we referred to as the hdrRM operon. In this study, we determined that the HdrRM system controls the expression of an analogous uncharacterized regulatory system annotated as SMU.2080 and SMU.2081. Like hdrRM, the SMU.2080-2081 operon encodes a LytTR family transcription regulator and putative membrane protein, which we now refer to as BrsR and BrsM respectively. Examination of the regulatory mechanism of the BrsRM system suggests that BrsM serves to antagonize the function of the transcription regulator BrsR. Further analyses of the regulatory role of BrsR determined that it functions as a transcription activator for a variety of bacteriocins and bacteriocin-related genes. In vitro electromobility shift assays confirmed that BrsR binds to the promoter regions of several bacteriocin genes and requires the presence of a LytTR family consensus direct repeat in order to stably bind DNA. In addition, we identified a novel regulatory scheme in which both the HdrRM and BrsRM systems coregulate each other and ultimately determine whether bacteriocin production will inhibit competitor organisms or result in lethality to the producer.
PLoS pathogens, 2016
Pneumococcal bacteriocins (pneumocins) are antibacterial toxins that mediate intra-species competition within the human host. However, the triggers of pneumocin expression are poorly understood. Using RNA-sequencing, we mapped the regulon of the pneumocin cluster (blp) of Streptococcus pneumoniae D39. Furthermore, by analogy with pneumococcal competence, we show that several antibiotics activate the blp-genes. Using real-time gene expression measurements we show that while the promoter driving expression of the two-component regulatory system blpR/H is constitutive, the remaining blp-promoters that control pneumocin expression, immunity and the inducer peptide BlpC, are pH-dependent and induced in the late exponential phase. Intriguingly, competence for genetic transformation, mediated by the paralogous ComD/E two-component quorum system, is induced by the same environmental cues. To test for interplay between these regulatory systems, we quantified the regulatory response to the ad...
Molecular Microbiology, 2005
It is important to ensure DNA availability when bacterial cells develop competence. Previous studies in Streptococcus pneumoniae demonstrated that the competence-stimulating peptide (CSP) induced autolysin production and cell lysis of its own non-competent cells, suggesting a possible active mechanism to secure a homologous DNA pool for uptake and recombination. In this study, we found that in Streptococcus mutans CSP induced co-ordinated expression of competence and mutacin production genes. This mutacin (mutacin IV) is a non-lantibiotic bacteriocin which kills closely related Streptococcal species such as S. gordonii. In mixed cultures of S. mutans and S. gordonii harbouring a shuttle plasmid, plasmid DNA transfer from S. gordonii to S. mutans was observed in a CSP and mutacin IV-dependent manner. Further analysis demonstrated an increased DNA release from S. gordonii upon addition of the partially purified mutacin IV extract. On the basis of these findings, we propose that Streptococcus mutans, which resides in a multispecies oral biofilm, may utilize the competence-induced bacteriocin production to acquire transforming DNA from other species living in the same ecological niche. This hypothesis is also consistent with a well-known phenomenon that a large genomic diversity exists among different S. mutans strains. This diversity may have resulted from extensive horizontal gene transfer.