V: Strain-specific regulatory role of eukaryote-like serine/threonine phosphatase in pneumococcal adherence. Infect Immun 2012

Streptococcus pneumoniae exploits a battery of virulence factors to colonize the host. Although the eukaryote-like Ser/Thr kinase of S. pneumoniae (StkP) has been implicated in physiology and virulence, the role of its cotranscribing phosphatase (PhpP) has remained elusive. The construction of nonpolar markerless phpP knockout mutants (phpP) in two pathogenic strains, D39 (type 2) and 6A-EF3114 (type 6A), indicated that PhpP is not indispensable for pneumococcal survival. Further, PhpP also par-ticipates in the regulation of cell wall biosynthesis/division, adherence, and biofilm formation in a strain-specific manner. Addi-tionally, we provide hitherto-unknown in vitro and in vivo evidence of a physiologically relevant biochemical link between the StkP/PhpP-mediated cognate regulation and the two-component regulatory system TCS06 (RR06/HK06) that regulates the ex-pression of the gene encoding an important pneumococcal surface adhesin, CbpA, which was found to be significantly upregu-lated inphpPmutants. In particular, StkP (threonine)-phosphorylated RR06 bound to the cbpA promoter with high efficiency even in the absence of the HK06-responsive and catalytically active aspartate 51 residue. Together, our findings unravel the sig-nificant contributions of PhpP in pneumococcal physiology and adherence. Streptococcus pneumoniae (pneumococcus), a Gram-positivepathogen, remains a significant health threat to both children and adults worldwide, despite the availability of antibiotics and polysaccharide-based vaccines (9, 37). The astounding ability of pneumococcus to alter its serotypes poses a major challenge i