Fig 1.

Motility and flagellin expression are dispensable for L. pneumophila virulence in G. mellonella. (A) In single pulmonary infections of C57BL/6 mice, the L. pneumophila 130b ΔflaA strain replicated to higher numbers at 72 h p.i. than the parental wild-type strain (P = 0.0003; Mann-Whitney). (B) Ten G. mellonella larvae were infected with 10⁷ CFU of WT, ΔdotA, or ΔflaA L. pneumophila 130b, and mortality was monitored for 72 h. Deletion of the flaA gene did not affect mortality compared to WT-infected larvae. (C) Hemolymph from larvae infected as described above was extracted at 0, 5, 18, and 24 h p.i., and the CFU/0.1 g of extracted hemolymph were enumerated. The WT and ΔflaA strains replicated similarly, and no significant difference was observed. The ΔdotA strain was cleared by 18 h p.i. Results are means of three independent experiments ± standard deviations. (D) G. mellonella larvae were infected with 10⁵ or 10⁶ CFU of the WT or ΔflaA strains, and mortality was monitored. For both strains, no mortality was observed when larvae were infected with 10⁵ CFU. In larvae infected with 10⁶ CFU, some death was seen; however, no significant differences between strains were observed. Results are representative of two independent experiments.