title: Analysis of the RpoS regulon in Borrelia burgdorferi in response to mammalian host signals provides insight into RpoS function during the enzootic cycle.
abstract: Borrelia burgdorferi (Bb) adapts to its arthropod and mammalian hosts by altering its transcriptional and antigenic profiles in response to environmental signals associated with each of these milieus. In studies presented here, we provide evidence to suggest that mammalian host signals are important for modulating and maintaining both the positive and negative aspects of mammalian host adaptation mediated by the alternative sigma factor RpoS in Bb. Although considerable overlap was observed between genes induced by RpoS during growth within the mammalian host and following temperature-shift, comparative microarray analyses demonstrated unequivocally that RpoS-mediated repression requires mammalian host-specific signals. A substantial portion of the in vivo RpoS regulon was uniquely upregulated within dialysis membrane chambers, further underscoring the importance of host-derived environmental stimuli for differential gene expression in Bb. Expression profiling of genes within the RpoS regulon by quantitative reverse transcription polymerase chain reaction (qRT-PCR) revealed a level of complexity to RpoS-dependent gene regulation beyond that observed by microarray, including a broad range of expression levels and the presence of genes whose expression is only partially dependent on RpoS. Analysis of Bb-infected ticks by qRT-PCR established that expression of rpoS is induced during the nymphal blood meal but not within unfed nymphs or engorged larvae. Together, these data have led us to postulate that RpoS acts as a gatekeeper for the reciprocal regulation of genes involved in the establishment of infection within the mammalian host and the maintenance of spirochetes within the arthropod vector.
authors.affiliation: Department of Medicine, University of Connecticut Health Center, Farmington, CT 06030, USA. mcaima@up.uchc.edu
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Caimano
authors.forename: Radha
authors.initials: R
authors.lastname: Iyer
authors.forename: Christian H
authors.initials: CH
authors.lastname: Eggers
authors.forename: Cynthia
authors.initials: C
authors.lastname: Gonzalez
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Morton
authors.forename: Michael A
authors.initials: MA
authors.lastname: Gilbert
authors.forename: Ira
authors.initials: I
authors.lastname: Schwartz
authors.forename: Justin D
authors.initials: JD
authors.lastname: Radolf
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D025065:Borrelia burgdorferi / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006790:Host-Parasite Interactions; D007303:Insect Vectors / Q000382:microbiology; D008193:Lyme Disease; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D018085:Regulon; D016415:Sequence Alignment; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013987:Ticks / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria