ClpP of Streptococcus mutans Differentially Regulates Expression of Genomic Islands, Mutacin Production, and Antibiotic Tolerance

Abstract

Streptococcus mutans is the primary etiological agent of human dental caries and, at times, of infective endocarditis. Within the oral cavity, the pathogen is subjected to conditions of stress. A well-conserved protein complex named ClpP (caseinolytic protease) plays a vital role in adaptation under stress conditions. To gain a better understanding of the global role of the ClpP protease in cellular homeostasis, a transcriptome analysis was performed using a ⌬clpP mutant strain. The expression levels of more than 100 genes were up-or downregulated in the ⌬clpP mutant compared to the wild type. Notably, the expression of genes in several genomic islands, such as TnSmu1 and TnSmu2, was differentially modulated in the ⌬clpP mutant strain. ClpP deficiency also increased the expression of genes associated with a putative CRISPR locus. Furthermore, several stress-related genes and genes encoding bacteriocin-related peptides and many transcription factors were also found to be altered in the ⌬clpP mutant strain. A comparative analysis of the two-dimensional protein profile of the wild type and the ⌬clpP mutant strains showed altered protein profiles. Comparison of the transcriptome data with the proteomic data identified four common gene products, suggesting that the observed altered protein expression of these genes could be due to altered transcription. The results presented here indicate that ClpP-mediated proteolysis plays an important global role in the regulation of several important traits in this pathogen.

Transcriptome analysis reveals that ClpXP proteolysis controls key virulence properties of Streptococcus mutans

“…Deferred antagonism assays confirmed the microarray results and revealed that both DclpP and DclpX were unable to inhibit growth of mutacin IV-and mutacin V-sensitive strains. Despite the limited overlap of genes found to be differentially expressed in our DclpP microarrays and in a previous report (Chattoraj et al, 2010), it is interesting to note that the data regarding expression of bacteriocin-related genes and bacteriocin production between both studies were in full agreement.…”

“…Clp-dependent proteolysis is of particular relevance in Streptococcus, as this genus lacks other known cytoplasmic proteases, such as Lon and ClpYQ (Kajfasz et al, 2009). In fact, proteolysis mediated through ClpXP is an important trait for stress tolerance, gene regulation and virulence in several Gram-positive pathogens (Chastanet et al, 2001;Chattoraj et al, 2010;Frees et al, 2003Frees et al, , 2004Gaillot et al, 2000;Ibrahim et al, 2005;Kwon et al, 2004). Previously, we demonstrated that a number of virulence properties of S. mutans, including stress tolerance, biofilm formation and colonization in a rodent caries model, were influenced by ClpXP proteolysis (Kajfasz et al, 2009 Here, we used microarrays to better understand the global effects of ClpXP proteolysis in S. mutans.…”

Pleiotropic Regulation of Virulence Genes in Streptococcus mutans by the Conserved Small Protein SprV

“…Loss of SprV causes an increase in the transcript levels of clpP. Our laboratory has previously shown that ClpP is involved in mutacin production, antibiotic stress tolerance, and control of gene expression from TnSmu1 and TnSmu2 genomic islands (31). Although our transcriptomic data aligned with the observed phenotypes, it was impossible to predict how SprV affects gene expression because of the largely interconnected pathways affecting these cellular processes.…”

Bacterial Genome Instability

“…In Thermus thermophilus, phage infections induce the transcription of cas genes and CRISPR arrays by a sensing mechanism using the cell's cyclic AMP receptor proteins (301,302). Stress, such as phage infection, the accumulation of misfolded proteins in the E. coli membrane, or the absence of ClpP in Streptococcus mutans, can also activate the expression of certain Cas proteins (303,304).…”