Competence‐specific induction of recA is required for full recombination proficiency during transformation in Streptococcus pneumoniae

Abstract

SummaryTranscriptional activation of the recA gene of Streptococcus pneumoniae was previously shown to occur at competence. A 5.7 kb recA-specific transcript that contained at least two additional genes, cinA and dinF, was identified. We now report the complete characterization of the recA operon and investigation of the role of the competence-specific induction of recA. The 5.7 kb competence-specific recA transcript is shown to include lytA, which encodes the pneumococcal autolysin, a protein previously shown to contribute to virulence of S. pneumoniae. Uncoupling (denoted Ind ¹ ) of recA and/or the downstream genes was achieved through the placement of transcription terminators within the operon, either upstream or downstream of recA. Prevention of the competencespecific induction of recA severely affected spontaneous transformation. Transformation efficiencies of recA þ (Ind ¹ ) and of wild-type cells were compared under various conditions and with different donor DNA. Chromosomal transformation was reduced 17-(chromosomal donor) to 45-fold (recombinant plasmid donor), depending on the donor DNA, and plasmid establishment was reduced 129-fold. Measurement of uptake of radioactively labelled donor DNA in transformed cells in parallel with scoring for transformants (chromosomal donor) revealed normal uptake, but a 21-fold reduction in recombination in a recA þ (Ind ¹ ) strain, indicating that the transformation defect was primarily in recombination. Strikingly enough, a much larger (460-fold) reduction in recombination was observed for the shortest homologous donor fragment used (878 nucleotides long). Possible interpretations of the observation that basal RecA appears unable to promote efficient recombination whatever the number and the length of donor fragments taken up are proposed. The role of recA induction is discussed in view of the potential contribution of transformation to genome plasticity in this pathogen.

Complete genome sequence of an M1 strain of Streptococcus pyogenes

“…A number of genes present in strain SF370 specify proteins with varying degrees of sequence similarity to competence-related genes from the oral streptococci, S. pneumoniae, and B. subtilis. In pneumococci, the genes for recA, cinA, and dinF are transcribed as a single 5.7-kb transcript, where their coordinated expression appears to be necessary for efficient incorporation of donor DNA during transformation (40). The recA and cinA genes of SF370 are also positioned together; however, the only possible gene similar to dinF is found in a distant part of the genome.…”

Competence-induced protein Ccs4 facilitates pneumococcal invasion into brain tissue and virulence in meningitis

“…Those early genes participate in competence regulation and link signals to late gene expression [23], while deletion of late genes, such as coiA, celA , and celB , abolishes transformation [15,24]. Although it has been reported that deletion of late genes, including lytA, cibAB , and cbpD , decreased pneumococcal virulence in mouse models of pneumonia and bacteremia, many of the genes in that study were hypothetical or conserved hypothetical proteins, and their roles in pneumococcal pathogenesis are unknown [25].…”

Characterization of the MSMEG_2631 Gene ( mmp ) Encoding a Multidrug and Toxic Compound Extrusion (MATE) Family Protein in Mycobacterium smegmatis and Exploration of Its Polyspecific Nature Using Biolog Phenotype MicroArray

“…The genomic organization of MATE efflux pump gene flanking regions has been studied in DinFs in several bacteria (24,(56)(57)(58). In E. coli and Streptococcus pneumoniae, dinF is in operons with lexA and recA, respectively (56,57).…”

“…In E. coli and Streptococcus pneumoniae, dinF is in operons with lexA and recA, respectively (56,57). In Staphylococcus aureus, the mepRAB operon encodes a MarR-like transcriptional regulator (mepR), a MATE family efflux pump (mepA), and a hypothetical protein (mepB) (24).…”