Protein Serine/Threonine Kinase StkP Positively Controls Virulence and Competence in Streptococcus pneumoniae

Abstract

In the Streptococcus pneumoniae genome, stkP, encoding a membrane-associated serine/threonine kinase, is not redundant (L. Novakova, S. Romao, J. Echenique, P. Branny, and M.-C. Trombe, unpublished results). The data presented here demonstrate that StkP belongs to the signaling network involved in competence triggering in vitro and lung infection and bloodstream invasion in vivo. In competence, functional StkP is required for activation of comCDE upstream of the autoregulated ring orchestrated by the competence-stimulating peptide. This is the first description of positive regulation of comCDE transcription in balance with its repression by CiaRH.The human pathogen Streptococcus pneumoniae is highly versatile. Its response to environment determines the bacterium's virulence and transformability as shown by mutational studies targeting metabolic (1, 16), regulatory (4, 11), transport (5, 19), and signaling (6, 8) functions. The factors so far identified which influence the fate of the bacterium include mainly the concentrations of divalent cations (5,19,20) and H ϩ and dioxygen (6). Signaling involves two-component signal-transducing systems (6,8,13), an oxidase (7), and a global regulator (4). In the present work, we provide evidence for the role of the serine/threonine kinase StkP in competence signaling and in experimental virulence. StkP is membrane associated, carries the PASTA signature (22), and has been shown to avoid LytA-dependent autolysis induced by growth at alkaline pH and by low concentrations of cell wall-directed antibiotics. It is proposed that virulence expression and competence development represent population responses to cell wall stress induced in specific growth conditions. The rough S. pneumoniae RX derivatives (19) carrying the lytA mutation (17) and the smooth serotype 2 (2) strain D39 and serotype 6 strain 23477 (1) were used for competence tests and virulence studies, respectively. Bacterial growth and storage were as previously described (12,17,19). An insertion mutation in stkP was obtained in vitro with the pBluescript derivative (15) plasmid pPHK29 carrying a 2.96-kbp EcoRI/ SalI amplimer containing stkP from the RX chromosome. The 1.3-kbp BamHI fragment from pPJ1 (14) containing the aphA3 cassette was inserted into a BglII site of stkP to give the mutagenic plasmid pPKB3. The mutated stkP::aphA3 allele was introduced by genetic transformation into the relevant genetic backgrounds, and strains carrying the allelic exchange were selected on kanamycin (50 mg/liter) plates as described previously (6). Recombinant clones were verified by PCR, and it has been verified that the stkP::aphA3 mutation did not affect bacterial growth of the different strains in vitro and also that the insertion mutation was very unlikely to impact the expression of downstream genes in the region. Indeed, with the software described in reference 9, it is predicted that genes SP1731 and SP1732 following the stkP stop codon show no relationship with stkP. Moreover, in the 118-bp intergenic region between stkP ...

A eukaryotic-type Ser/Thr kinase in Enterococcus faecalis mediates antimicrobial resistance and intestinal persistence

“…Homologs of PrkC in some pathogenic streptococci are required for full virulence in animal models of infection (21,23), suggesting that the streptococcal PrkC homologs regulate the expression or activity of virulence factors in their respective hosts. These streptococcal PrkC homologs each exhibit a PrkClike bipartite domain architecture including PASTA domains, suggesting that, like E. faecalis PrkC, they detect perturbations of the cell envelope as sensory input.…”

Eukaryote-Like Serine/Threonine Kinases and Phosphatases in Bacteria

“…Homologs of PrkC have also been implicated in S. pyogenes adherence and invasion and in E. faecalis persistence (72,82). The involvement of eSTKs in virulence has also been reported for several other pathogens, such as Streptococcus pneumoniae, E. faecalis, Pseudomonas aeruginosa, and Salmonella enterica serovar Typhi (33,43,46,(144)(145)(146)191).…”

Control of cell division in Streptococcus pneumoniae by the conserved Ser/Thr protein kinase StkP

“…A strain in which stkP is deleted is still viable in vitro but grows more slowly, is less competent for genetic transformation, and is more susceptible to several environmental stresses (29)(30)(31)(32). StkP also plays an essential role for in vivo survival, because stkP mutants were strongly attenuated in virulence in mouse models (29,30). Phenotypic analysis, through both transmission electron microscopy and differential interference contrast microscopy, showed that stkP mutants often are elongated, suggesting a defect in cell division (30,33).…”

“…PASTA domains of StkP were shown to bind synthetic and native PG subunits and β-lactam antibiotics (28). A strain in which stkP is deleted is still viable in vitro but grows more slowly, is less competent for genetic transformation, and is more susceptible to several environmental stresses (29)(30)(31)(32). StkP also plays an essential role for in vivo survival, because stkP mutants were strongly attenuated in virulence in mouse models (29,30).…”