Identification of non-dot/icm suppressors of the Legionella pneumophila DeltadotL lethality phenotype.
Legionella pneumophila, a causative agent of bacterial pneumonia, survives inside phagocytic cells by avoiding rapid targeting to the lysosome. This bacterium utilizes a type IVB secretion system, encoded by the dot/icm genes, to replicate inside host cells. DotL, a critical component of the Dot/Icm secretion apparatus, functions as the type IV coupling protein. In contrast to most dot/icm genes, which are dispensable for growth on bacteriological media, dotL is required for the viability of wild-type L. pneumophila. Previously we reported that DeltadotL lethality could be suppressed by inactivation of the Dot/Icm complex via mutations in other dot/icm genes. Here we report the isolation of non-dot/icm suppressors of this phenotype. These DeltadotL suppressors include insertions that disrupt the function of the L. pneumophila homologs of cpxR, djlA, lysS, and two novel open reading frames, lpg0742 and lpg1594, that we have named ldsA and ldsB for lethality of DeltadotL suppressor. In addition to suppressing DeltadotL lethality, inactivation of these genes in a wild-type strain background causes a range of defects in L. pneumophila virulence traits, including intracellular growth, implicating these factors in the proper function of the Dot/Icm complex. Consistent with previous data showing a role for the cpx system in regulating expression of several dot/icm genes, the cpxR insertion mutant produced decreased levels of three Dot/Icm proteins, DotA, IcmV, and IcmW. The remaining four suppressors did not affect the steady-state levels of any Dot/Icm protein and are likely to represent the first identified factors necessary for assembly and/or activation of the Dot/Icm secretion complex.
Vincent
Carr D
CD
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Buscher
Benjamin A
BA
Friedman
Jonathan R
JR
Williams
Lee Anne
LA
Bardill
Patrick
P
Vogel
Joseph P
JP
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics; D005798:Genes, Bacterial; D016153:Genes, Suppressor; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D016952:Legionella pneumophila / Q000235:genetics* / Q000254:growth & development; D007877:Legionnaires' Disease / Q000382:microbiology; D008264:Macrophages / Q000382:microbiology; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D018832:Molecular Chaperones / Q000235:genetics; D005810:Multigene Family; D016366:Open Reading Frames; D015398:Signal Transduction / Q000235:genetics*; D013489:Suppression, Genetic
D001426:Bacterial Proteins; D002352:Carrier Proteins; C440002:DotA protein, Legionella pneumophila; C501057:DotL protein, Legionella pneumophila; D050956:HSP40 Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; C085504:CpxR protein, Bacteria