FIG. 2.

Levels of pigment in culture supernatants of wild-type and hmgA mutant L. pneumophila. Wild-type 130b (black bars), hmgA mutant NU326 (white bars), and complemented mutant NU326 (gray bars) were inoculated into standard BYE (A) or deferrated CDM (B) and then, after the indicated periods of incubation at 37°C, filter-sterilized, culture supernatants were assessed for pigment production as measured by their OD₄₀₀ over that of medium controls. For ease of visualization, the inset in panel B repeats the data for the wild-type and complemented mutant strains with a smaller scale on the y axis. The data presented are the means and standard deviations from triplicate cultures for each strain. The results presented are representative of at least three replicate experiments in which triplicate cultures for each strain were examined and found to have a level of variation comparable to that presented here. When grown in CDM, the increases in pigment expression by the hmgA mutant NU326 were significant at all time points (P < 0.01). When grown in BYE, pigment expression by the mutant was consistently greater than that of wild type; however, the difference did not achieve the statistical significance seen with CDM cultures.