FIG 4.

Effect of rpoN overexpression on PilE levels in N. meningitidis. (A) S4P_lac-rpoN^Nm was grown overnight on solid medium in the presence or absence of IPTG to induce σ^N expression. Pilin expression was detected by Western blotting with an antipeptide antibody. Expression of σ^N was verified using anti-FLAG antibodies. No change in pilin expression was detected in the presence of σ^N. (B) S4P_lac-rpoN^Nel and control strain S4 ery were grown overnight on solid medium with or without IPTG. N. elongata σ^N was detected using anti-FLAG antibodies. Expression of σ^N from N. elongata in S4 led to a reduction in pilin expression, while no reduction was observed in the control strain. The asterisk indicates a degradation product of Nel σ^N-FLAG. (C) Similarly, a reduced level of pilin was detected in S4P_lac-rpoN^Nel grown in liquid medium in the presence of IPTG for 1, 3, 5, and 6 h compared to that without the inducer. Expression of RecA or Coomassie blue staining of extracts was used as a control. Numbers to the left indicate the positions of molecular weight markers (kilodaltons).