FIG. 2.
LOS-deficient N. meningitidis bacteria are more susceptible to LL-37-mediated killing. (A) N. meningitidis strain FAM20 (serogroup C) and the isogenic lpxA mutant strain lacking LOS, after being resuspended to form 105 CFU/ml, were incubated with LL-37 (0 to 16 μΜ) for 3 h. Viable counts were determined, with data presented as mean survival ratios ± standard errors (n = 3). (B) The FAM20 strain and the isogenic lpxA mutant strain, after being resuspended to 108 CFU/ml, were treated with LL-37 (0 to 500 nM) for 30 min at 22°C and subsequently fixed and stained using a biotinylated anti-LL-37 antibody before analysis by flow cytometry. The numbers of LL-37-binding bacteria are expressed as percentages of the total number of bacteria. Data are presented as mean percentages + standard errors (n = 3). (C) Representative histogram plots showing LL-37 binding to the FAM20 strain and the lpxA mutant strain after incubation with 125 nM LL-37. * and ** represent statistically significant differences (P ≤ 0.01 and P ≤ 0.05, respectively).