title: Genome-wide screen for temperature-regulated genes of the obligate intracellular bacterium, Rickettsia typhi.
abstract: BACKGROUND
  The ability of rickettsiae to survive in multiple eukaryotic host environments provides a good model for studying pathogen-host molecular interactions. Rickettsia typhi, the etiologic agent of murine typhus, is a strictly intracellular gram negative alpha-proteobacterium, which is transmitted to humans by its arthropod vector, the oriental rat flea, Xenopsylla cheopis. Thus, R. typhi must cycle between mammalian and flea hosts, two drastically different environments. We hypothesize that temperature plays a role in regulating host-specific gene expression, allowing R. typhi to survive in mammalian and arthropod hosts. In this study, we used Affymetrix microarrays to screen for temperature-induced genes upon a temperature shift from 37 degrees C to 25 degrees C, mimicking the two different host temperatures in vitro.
  
  
  RESULTS
  Temperature-responsive genes belonged to multiple functional categories including among others, transcription, translation, posttranslational modification/protein turnover/chaperones and intracellular trafficking and secretion. A large number of differentially expressed genes are still poorly characterized, and either have no known function or are not in the COG database. The microarray results were validated with quantitative real time RT-PCR.
  
  
  CONCLUSIONS
  This microarray screen identified various genes that were differentially expressed upon a shift in temperature from 37 degrees C to 25 degrees C. Further characterization of the identified genes may provide new insights into the ability of R. typhi to successfully transition between its mammalian and arthropod hosts.
authors.affiliation: Department of Microbiology and Immunology, University of Maryland, 660 W, Redwood Street, Room HH324B, Baltimore, MD 21201, USA. sdreh001@umaryland.edu
authors.forename: Sheila M
authors.initials: SM
authors.lastname: Dreher-Lesnick
authors.forename: Shane M
authors.initials: SM
authors.lastname: Ceraul
authors.forename: M Sayeedur
authors.initials: MS
authors.lastname: Rahman
authors.forename: Abdu F
authors.initials: AF
authors.lastname: Azad
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002460:Cell Line; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics; D051379:Mice; D018832:Molecular Chaperones / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012286:Rickettsia typhi / Q000235:genetics* / Q000378:metabolism; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones