FIG. 6.
Deletion of most dot/icm genes can suppress the lethality caused by deletion of dotL. A dotL/ΔdotL::CmR merodiploid was constructed in a variety of different dot/icm backgrounds. Sucrose-resistant recombinants were selected and then screened for the ΔdotL allele by resistance to chloramphenicol. ΔdotL recombinants could not be obtained from the dotL/ΔdotL::Cmr merodiploid strain JV1003. The presence of a wild-type copy of dotL on a low-copy vector allowed the isolation of ΔdotL recombinants (JV1003 plus dotL). Inactivation of 20 of 23 dot/icm genes suppressed the loss of dotL. In addition, deletion of citA/tphA, a housekeeping gene found near the dot/icm genes, did not allow loss of dotL (42). In contrast, dotL is not essential in a related L. pneumophila strain, JR32. The data shown reflects the average number of ΔdotL recombinants recovered from scoring 50 events from four independent experiments.