Alternate sigma factor RpoS is required for the in vivo-specific repression of Borrelia burgdorferi plasmid lp54-borne ospA and lp6.6 genes.
While numerous positively regulated loci have been characterized during the enzootic cycle of Borrelia burgdorferi, very little is known about the mechanism(s) involved in the repression of borrelial loci either during tick feeding or within the mammalian host. Here, we report that the alternative sigma factor RpoS is required for the in vivo-specific repression of at least two RpoD-dependent B. burgdorferi loci, ospA and lp6.6. The downregulation of ospA and Ip6.6 appears to require either a repressor molecule whose expression is RpoS dependent or an accessory factor which enables RpoS to directly interact with the ospA and Ip6.6 promoter elements, thereby blocking transcription by RpoD. The central role for RpoS during the earliest stages of host adaptation suggests that tick feeding imparts signals to spirochetes that trigger the RpoS-dependent repression, as well as expression, of in vivo-specific virulence factors critical for the tick-to-mammalian host transition.
Caimano
Melissa J
MJ
Department of Medicine, University of Connecticut Health Center, Farmington, 06030-3715, USA. mcaima@up.uchc.edu
Eggers
Christian H
CH
Gonzalez
Cynthia A
CA
Radolf
Justin D
JD
D000222:Adaptation, Physiological / Q000235:genetics; D000954:Antigens, Surface / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D001428:Bacterial Vaccines; D025065:Borrelia burgdorferi / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D050939:Gene Fusion; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D008074:Lipoproteins / Q000235:genetics*; D010957:Plasmids / Q000235:genetics*; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D008074:Lipoproteins; C072045:OspA protein; D012808:Sigma Factor; C103952:lipoprotein lp6.6, Borrelia burgdorferi; C069567:sigma factor KatF protein, Bacteria; D049452:Green Fluorescent Proteins