FIG. 2.

Low-temperature growth of the wild type and ppiB and lpg1962 mutants of L. pneumophila on BCYE agar. (A) Tenfold serial dilutions of wild-type strain 130b, ppiB mutant NU340, lpg1962 mutant NU342, ppiB lpg1962 double mutant NU344, and lspF mutant NU275 containing equivalent numbers of CFU (as determined at 37°C) were spotted onto BCYE agar plates and then incubated at either 37°C (left panel) or 17°C (right panel). Images of bacterial growth were then obtained after 3 days for the 37°C plates and after 20 days for the 17°C plates. The results are representative of at least three independent experiments. (B) Tenfold serial dilutions of wild-type strain 130b and ppiB mutant NU340 containing either the vector pMMB2002 or the complementing plasmid pMB3 (i.e., ppiB cloned into pMMB2002) were spotted onto BCYE agar and then incubated at 37°C (left panel) or 17°C (right panel). Images of bacterial growth were then obtained as described above. For unknown reasons, the vector alone slowed the growth of both the wild type and the mutant at 17°C (compared to the 17°C cultures used for panel A). Nonetheless, the specific growth-stimulating effect of cloned ppiB on NU340 at 17°C is still evident. The results are representative of two independent experiments.