Fig. 1.

Construction of a markerless THpep27 mutant. (A) Transcription of the pep27 locus and insertion and orientation of the Cheshire cassette. The numbers represent nucleotide sequence numbers in the D39 wild type (D39WT) genome. A THpep27 mutant with a pep27 deletion was constructed. (B) Identification of the THpep27 mutant. Streptococcus pneumoniae D39 and its isogenic THpep27 mutant were cultured in THY broth until mid-log phase, bacterial RNA was extracted, and mRNA levels of pep27 and 16s RNA were analyzed by reverse transcription polymerase chain reaction.