Growth of wild-type and <i>phhA</i> mutant <i>L. pneumophila</i> in CDM containing different amounts of tyrosine.

<p><i>L. pneumophila</i> 130b wild-type (WT) and <i>phhA</i> mutant strains NU406 and NU407 were inoculated into either standard CDM containing tyrosine (A) or CDM lacking tyrosine (B) and at the indicated time points, the extent of bacterial growth was determined by recording the optical density (OD) of the cultures. In panel (B), the ODs of the mutant cultures were significantly less than that of the WT cultures at 18, 24, and 40 h post-inoculation, as indicated by the asterisks (<i>P</i><0.05, Student’s <i>t</i>-test). (C) WT and mutant NU406 carrying the empty vector (pMMB2002) and NU406 carrying the <i>phhA</i> gene cloned into pMMB2002 (i.e., pPhhA) were cultured in CDM without the tyrosine supplement and then at 24 h post-inoculation the OD of the cultures were determined. The OD of the NU406 (pMMB2002) culture was significantly less than that of both the WT and the complemented mutant (<i>P</i><0.05, Student’s <i>t</i>-test). All experiments are representative of three independent trials.