Global Transcriptional Analysis of clpP Mutations of Type 2 Streptococcus pneumoniae and Their Effects on Physiology and Virulence

Abstract

ABSTRACT Streptococcus pneumoniae is an important human pathogen that contains single copies of genes encoding the ClpP and FtsH ATP-dependent proteases but lacks the Lon and HslV proteases. We constructed and characterized the phenotypes of clpP , clpC , and clpX deletion replacement mutants, which lack the ClpP protease subunit or the putative ClpC or ClpX ATPase specificity factor. A Δ clpP mutant, but not a Δ clpC or Δ clpX mutant, of the virulent D39 type 2 strain of S. pneumoniae grew poorly at 30°C and failed to grow at 40°C. Despite this temperature sensitivity, transcription of the heat shock regulon determined by microarray analysis was induced in a Δ clpP mutant, which was also more sensitive to oxidative stress by H 2 O 2 and to puromycin than its clpP + parent strain. A Δ clpP mutant, but not a Δ clpC mutant, was strongly attenuated for virulence in the murine lung and sepsis infection models. All of these phenotypes were complemented in a Δ clpP / clpP + merodiploid strain. Consistent with these complementation patterns, clpP was found to be in a monocistronic operon, whose transcription was induced about fivefold by heat shock in S. pneumoniae as determined by Northern and real-time reverse transcription-PCR analyses. Besides clpP , transcription of clpC , clpE , and clpL , but not clpX or ftsH , was induced by heat shock or entry into late exponential growth phase. Microarray analysis of Δ clpP mutants showed a limited change in transcription pattern (≈80 genes) consistent with these phenotypes, including repression of genes involved in oxidative stress, metal ion transport, and virulence. In addition, transcription of the early and late competence regulon was induced in the Δ clpP mutant, and competence gene expression and DNA uptake seemed to be constitutively induced throughout growth. Together, these results indicate that ClpP-mediated proteolysis plays a complex and central role in numerous pneumococcal stress responses, development of competence, and virulence.