FIG. 4.
Alterations of LLO's N-terminal residue have at most weak effects on the intracellular growth of L. monocytogenes. (A and B) Growth curves of L. monocytogenes LLOWT (WT; expressing Lys-LLO) and LLOK25X mutants (identified by the corresponding mutations) in J774 macrophages (A) and NIH 3T3 fibroblasts (B) (see Materials and Methods). Shown here are the results, including standard deviations, of one of at least three independent experiments with triplicate coverslips for each experiment. The P values for the growth difference between the LLOWT and LLOK25X strains of L. monocytogenes were 0.008 and 0.035 at 8 and 11 h p.i., respectively (based on Student's t test for one sample; http://www.statpages.org). (C) Sizes of plaques formed in mouse L2 fibroblasts by L. monocytogenes strains that produced the indicated X-LLO proteins relative to the size of plaques formed by the wild-type strain expressing Lys-LLO, which was set as 100%. Standard deviations were compiled from the results of three independent experiments.