title: Interdependence of environmental factors influencing reciprocal patterns of gene expression in virulent Borrelia burgdorferi.
abstract: The paradigm for differential antigen expression in Borrelia burgdorferi, the agent of Lyme disease, is the reciprocal expression of its outer surface (lipo)proteins (Osp) A and C; as B. burgdorferi transitions from its arthropod vector into mammalian tissue, ospC is upregulated, and ospA is downregulated. In the current study, using B. burgdorferi cultivated under varying conditions in BSK-H medium, we found that a decrease in pH, in conjunction with increases in temperature (e.g. 34 degrees C or 37 degrees C) and cell density, acted interdependently for the reciprocal expression of ospC and ospA. The lower pH (6.8), which induced the reciprocal expression of ospC and ospA in BSK-H medium, correlated with a drop in pH from 7.4 to 6.8 of tick midgut contents during tick feeding. In addition to ospC and ospA, other genes were found to be regulated in reciprocal fashion. Such genes were either ospC-like (e.g. ospF, mlp-8 and rpoS) (group I) or ospA-like (lp6.6 and p22) (group II); changes in expression occurred at the mRNA level. That the expression of rpoS, encoding a putative stress-related alternative sigma factor (sigma(s)), was ospC-like suggested that the expression of some of the group I genes may be controlled through sigma(s). The combined results prompt a model that allows for predicting the regulation of other B. burgdorferi genes that may be involved in spirochaete transmission, virulence or mammalian host immune responses.
authors.affiliation: Department of Microbiology, University of Texas South-western Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75235, USA.
authors.forename: X
authors.initials: X
authors.lastname: Yang
authors.forename: M S
authors.initials: MS
authors.lastname: Goldberg
authors.forename: T G
authors.initials: TG
authors.lastname: Popova
authors.forename: G B
authors.initials: GB
authors.lastname: Schoeler
authors.forename: S K
authors.initials: SK
authors.lastname: Wikel
authors.forename: K E
authors.initials: KE
authors.lastname: Hagman
authors.forename: M V
authors.initials: MV
authors.lastname: Norgard
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial; D000954:Antigens, Surface / Q000235:genetics* / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001428:Bacterial Vaccines; D015748:Borrelia burgdorferi Group / Q000235:genetics* / Q000472:pathogenicity*; D015536:Down-Regulation; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D018884:Ixodes / Q000382:microbiology*; D008074:Lipoproteins; D022123:Lyme Disease Vaccines / Q000235:genetics* / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D013696:Temperature; D014158:Transcription, Genetic; D014774:Virulence / Q000235:genetics
chemical_list: D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D008074:Lipoproteins; D022123:Lyme Disease Vaccines; C072045:OspA protein; C079616:OspC protein; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria