Low-temperature growth of the wild type and ppiB and lpg1962 mutants of L. pneumophila in BYE broth. Log-phase bacteria were inoculated into BYE broth at 17°C, and then the growth of the indicated strains was monitored by recording the optical densities of the cultures at various times. (A) Comparison of the growth of wild-type strain 130b (•), ppiB mutant NU340 (○), lpg1962 mutant NU342 (▿), ppiB lpg1962 double mutant NU344 (▾), and lspF mutant NU275 (▪). (B) Comparison of the growth of wild-type strain 130b (•), ppiB mutant NU340 (○), and complemented ppiB mutant NU340 (pMB3) (□). The apparent differences in growth between either the ppiB mutant or the ppiB lpg1962 mutant and the wild-type strain or the complemented ppiB mutant were statistically significant, as were the differences in growth between the lspF mutant and the other strains (P < 0.05, Student's t test). The slight differences in optical densities at 660 nm (OD660) between the wild type and the lpg1962 mutant observed at some time points were not seen in repeat experiments. The data are the means and standard deviations for duplicate cultures and are representative of at least three (A) and two (B) independent experiments.