title: Enterohemorrhagic Escherichia coli biofilms are inhibited by 7-hydroxyindole and stimulated by isatin.
abstract: Since indole is present at up to 500 microM in the stationary phase and is an interspecies biofilm signal (J. Lee, A. Jayaraman, and T. K. Wood, BMC Microbiol. 7:42, 2007), we investigated hydroxyindoles as biofilm signals and found them also to be nontoxic interspecies biofilm signals for enterohemorrhagic Escherichia coli O157:H7 (EHEC), E. coli K-12, and Pseudomonas aeruginosa. The genetic basis of EHEC biofilm formation was also explored, and notably, virulence genes in biofilm cells were repressed compared to those in planktonic cells. In Luria-Bertani medium (LB) on polystyrene with quiescent conditions, 7-hydroxyindole decreased EHEC biofilm formation 27-fold and decreased K-12 biofilm formation 8-fold without affecting the growth of planktonic cells. 5-Hydroxyindole also decreased biofilm formation 11-fold for EHEC and 6-fold for K-12. In contrast, isatin (indole-2,3-dione) increased biofilm formation fourfold for EHEC, while it had no effect for K-12. When continuous-flow chambers were used, confocal microscopy revealed that EHEC biofilm formation was reduced 6-fold by indole and 10-fold by 7-hydroxyindole in LB. Whole-transcriptome analysis revealed that isatin represses indole synthesis by repressing tnaABC 7- to 37-fold in EHEC, and extracellular indole levels were found to be 20-fold lower. Furthermore, isatin repressed the AI-2 transporters lsrABCDFGKR, while significantly inducing the flagellar genes flgABCDEFGHIJK and fliAEFGILMNOPQ (which led to a 50% increase in motility). 7-Hydroxyindole induces the biofilm inhibitor/stress regulator ycfR and represses cysADIJPU/fliC (which led to a 50% reduction in motility) and purBCDEFHKLMNRT. Isogenic mutants showed that 7-hydroxyindole inhibits E. coli biofilm through cysteine metabolism. 7-Hydroxyindole (500 microM) also stimulates P. aeruginosa PAO1 biofilm formation twofold; therefore, hydroxyindoles are interspecies bacterial signals, and 7-hydroxyindole is a potent EHEC biofilm inhibitor.
authors.affiliation: Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, USA.
authors.forename: Jintae
authors.initials: J
authors.lastname: Lee
authors.forename: Tarun
authors.initials: T
authors.lastname: Bansal
authors.forename: Arul
authors.initials: A
authors.lastname: Jayaraman
authors.forename: William E
authors.initials: WE
authors.lastname: Bentley
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Wood
mesh_terms: D001483:Base Sequence; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D003545:Cysteine / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D048168:Escherichia coli K12 / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects; D005798:Genes, Bacterial / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D007510:Isatin / Q000494:pharmacology*; D009068:Movement / Q000187:drug effects; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D015398:Signal Transduction
chemical_list: C494864:7-hydroxyindole; D017931:DNA Primers; D004269:DNA, Bacterial; D007211:Indoles; D007510:Isatin; D003545:Cysteine