FIG. 5.

Optimal growth in L2 fibroblasts requires lipoate-dependent metabolism. The WT, the AlA2⁻ mutant, and the LLO⁻ mutant of L. monocytogenes were grown to the stationary phase in BHI medium and used to infect L2 cells for 1 h. Infected monolayers were washed and treated with 50 μg of gentamicin/ml. (A) A 3-ml agar overlay was placed over infected cells, and plaques allowed to develop for 5 days, at which time they were visualized by the addition of Neutral Red. Plaque diameters (n = 20) were measured and are expressed as percentages of the mean diameters of WT plaques. (B and C) Infected L2 cells were osmotically lysed and plated on LB agar to enumerate CFU. Error bars represent standard deviations.