Dose dependent inhibition of comX expression and genetic transformation by CSP1 analogs with substitution at glutamate residue in the first position.

(A) CSP1 analogs with substitution at the first glutamate acid competitively inhibit CSP1-mediated induction of comX. D39pcomX::lacZ cells were exposed to 100 ng/ml of CSP1 alone or simultaneously with increasing concentrations of CSP1 analogs. The activity of the comX gene promoter was measured by β-galactosidase activity. Experiments were performed in triplicates and repeated three times. The means ± SD of one typical experiment are shown. (B) CSP1 analogs with substitution at the first glutamate acid competitively inhibit the ability of CSP1 to induce genetic transformation. Genetic transformation was performed using the rpsL gene. Transformants were selected on THB agar containing 100 µg/ml streptomycin. Experiments were performed in triplicates and repeated three times. The means ± SD of one typical experiment are shown.