title: Indole can act as an extracellular signal in Escherichia coli.
abstract: Previous work has shown that lacZ fusions to the cysK, astD, tnaB, and gabT genes in Escherichia coli are activated by self-produced extracellular signals. Using a combination of ethyl acetate extraction, reversed-phase C(18) chromatography, and thin-layer chromatography, we have purified an extracellular activating signal from E. coli supernatants. Mass spectrometry revealed a molecule with an m/z peak of 117, consistent with indole. Nuclear magnetic resonance analysis of the purified E. coli factor and synthetic indole revealed identical profiles. Using synthetic indole, a dose-dependent activation was observed with lacZ fusions to the gabT, astD, and tnaB genes. However, cysK::lacZ and several control fusions were not significantly activated by indole. Conditioned medium prepared from a tnaA (tryptophanase) mutant, deficient in indole production, supported 26 to 41% lower activation of the gabT and astD fusions. The residual level of activation may be due to a second activating signal. Activation of the tnaB::lacZ fusion was reduced by greater than 70% in conditioned medium from a tnaA mutant.
authors: Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.
authors: D
authors: D
authors: Wang
authors: X
authors: X
authors: Ding
authors: P N
authors: PN
authors: Rather
mesh_terms: D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D017077:Culture Media, Conditioned; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007211:Indoles / Q000378:metabolism*; D007763:Lac Operon; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014368:Tryptophanase / Q000235:genetics
chemical_list: D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins; D017077:Culture Media, Conditioned; D029968:Escherichia coli Proteins; D007211:Indoles; D026901:Membrane Transport Proteins; D011993:Recombinant Fusion Proteins; C035131:TnaB protein, E coli; C030374:indole; D014368:Tryptophanase