title: Bacteria-host communication: the language of hormones.
abstract: The interbacterial communication system known as quorum sensing (QS) utilizes hormone-like compounds referred to as autoinducers to regulate bacterial gene expression. Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 is the agent responsible for outbreaks of bloody diarrhea in several countries. We previously proposed that EHEC uses a QS regulatory system to "sense" that it is within the intestine and activate genes essential for intestinal colonization. The QS system used by EHEC is the LuxS/autoinducer 2 (AI-2) system extensively involved in interspecies communication. The autoinducer AI-2 is a furanosyl borate diester whose synthesis depends on the enzyme LuxS. Here we show that an EHEC luxS mutant, unable to produce the bacterial autoinducer, still responds to a eukaryotic cell signal to activate expression of its virulence genes. We have identified this signal as the hormone epinephrine and show that beta- and alpha-adrenergic antagonists can block the bacterial response to this hormone. Furthermore, using purified and in vitro synthesized AI-2 we showed that AI-2 is not the autoinducer involved in the bacterial signaling. EHEC produces another, previously undescribed autoinducer (AI-3) whose synthesis depends on the presence of LuxS. These results imply a potential cross-communication between the luxS/AI-3 bacterial QS system and the epinephrine host signaling system. Given that eukaryotic cell-to-cell signaling typically occurs through hormones, and that bacterial cell-to-cell signaling occurs through QS, we speculate that QS might be a "language" by which bacteria and host cells communicate.
authors.affiliation: Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9048, USA. vanessa.sperandio@utsouthwestern.edu
authors.forename: Vanessa
authors.initials: V
authors.lastname: Sperandio
authors.forename: Alfredo G
authors.initials: AG
authors.lastname: Torres
authors.forename: Bruce
authors.initials: B
authors.lastname: Jarvis
authors.forename: James P
authors.initials: JP
authors.lastname: Nataro
authors.forename: James B
authors.initials: JB
authors.lastname: Kaper
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D013437:Carbon-Sulfur Lyases; D004837:Epinephrine / Q000378:metabolism; D004927:Escherichia coli Infections / Q000209:etiology / Q000378:metabolism / Q000382:microbiology; D019453:Escherichia coli O157 / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006367:HeLa Cells; D006714:Homoserine / Q000031:analogs & derivatives* / Q000235:genetics / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007783:Lactones; D009154:Mutation; D010750:Phosphoproteins; D015398:Signal Transduction; D014774:Virulence / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C457340:LEE protein, E coli; D007783:Lactones; C091088:N-octanoylhomoserine lactone; D010750:Phosphoproteins; D006714:Homoserine; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria; D004837:Epinephrine