FIG. 2.

pfs and luxS mutants of N. meningitidis have a growth defect that cannot be complemented by AI-2 provided in trans. (A and B) The growth of the N. meningitidis B16B6-pfs and B16B6-luxS mutants (▵) was compared to the growth of wild-type strain B16B6 (▪) and the B16B6-pfs pfs⁺ and B16B6-luxS luxS⁺ complemented mutants (⧫) in BHI rich medium (A) and in cysteine- and methionine-free c-DMEM (B). The data are the means ± standards deviations for three independent cultures. (Insets) Growth defects of mutants (open bars) compared to the wild type (black bars) and complemented mutants (gray bars) in BHI rich medium as confirmed by counting viable cells (CFU). (C) CI of the N. meningitidis B16B6-pfs or luxS mutant when grown together with wild-type strain B16B6 in BHI rich medium. (Insets) The presence of AI-2 in the supernatant at wild-type levels was guarantied by addition of DPD 30 min before the expected peak of AI-2 production and was confirmed by measurements at three time points (4.5 h [just before addition of DPD], 5 h, and 5.5 h). The CI was determined by determining the number of CFU of each bacterium in the mixed cultures, as described in Materials and Methods. The data are the means ± standard errors for three independent cultures.