FIG 2.

Transcription of the early and late com genes in the selected strains. The transcriptional reporter constructs were generated by fusion of the promoters of the early (comX) or late (ssbB) com genes to the 5′ end of the luciferase gene in pIB166 and electroporation into 11 nontransformable isolates. The promoter sequence of spxB was used as a positive control for transcription in the nontransformable isolates. The low-transformable (TH883 and TH2741), intermediate-transformable (TH906 and TH2835), and high-transformable (TH867 and TH2912) isolates, as well as strain R6, were used as positive controls for com gene transcription. The reporter strains were grown in THY to an OD₆₂₀ of ∼0.1 and treated with CSP (final concentration, 500 ng/ml) for 30 min before the measurement of the luciferase activities for the strains carrying the reporter construct of spxB (A), comX (B), or ssbB (C). The values are the means ± the standard errors of the results from triplicate samples. LT, low transformability; IT, intermediate transformability; HT, high transformability; NT, no transformability.