title: Functional genomic analysis of bile salt resistance in Enterococcus faecium.
abstract: BACKGROUND
  Enterococcus faecium is a Gram-positive commensal bacterium of the mammalian intestinal tract. In the last two decades it has also emerged as a multi-resistant nosocomial pathogen. In order to survive in and colonize the human intestinal tract E. faecium must resist the deleterious actions of bile. The molecular mechanisms exploited by this bacterium to tolerate bile are as yet unexplored.
  
  
  RESULTS
  In this study we used a high-throughput quantitative screening approach of transposon mutant library, termed Microarray-based Transposon Mapping (M-TraM), to identify the genetic determinants required for resistance to bile salts in E. faecium E1162. The gene gltK, which is predicted to encode a glutamate/aspartate transport system permease protein, was identified by M-TraM to be involved in bile resistance. The role of GltK in bile salt resistance was confirmed by the subsequent observation that the deletion of gltK significantly sensitized E. faecium E1162 to bile salts. To further characterize the response of E. faecium E1162 to bile salts, we performed a transcriptome analysis to identify genes that are regulated by exposure to 0.02% bile salts. Exposure to bile salts resulted in major transcriptional rearrangements, predominantly in genes involved in carbohydrate, nucleotide and coenzyme transport and metabolism.
  
  
  CONCLUSIONS
  These findings add to a better understanding of the molecular mechanisms by which E. faecium responds and resists the antimicrobial action of bile salts.
authors: Department of Medical Microbiology, University Medical Center Utrecht, Heidelberglaan 100; Room G04,527, Utrecht, 3584 CX, The Netherlands. x.zhang@umcutrecht.nl
authors: Xinglin
authors: X
authors: Zhang
authors: Damien
authors: D
authors: Bierschenk
authors: Janetta
authors: J
authors: Top
authors: Iacovos
authors: I
authors: Anastasiou
authors: Marc J M
authors: MJ
authors: Bonten
authors: Rob J L
authors: RJ
authors: Willems
authors: Willem
authors: W
authors: van Schaik
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D001646:Bile; D001647:Bile Acids and Salts / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D016984:Enterococcus faecium / Q000187:drug effects* / Q000235:genetics* / Q000254:growth & development; D040081:Protein Array Analysis; D059467:Transcriptome / Q000187:drug effects
chemical_list: D027322:Amino Acid Transport System X-AG; D001426:Bacterial Proteins; D001647:Bile Acids and Salts
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