title: The multifaceted roles of the interspecies signalling molecule indole in Agrobacterium tumefaciens.
abstract: Bacteria utilize signal molecules to ensure their survival in environmental niches, and indole is an interspecies and interkingdom signalling molecule, which is widespread in the natural environment. In this study, we sought to identify novel roles of indole in soil-borne bacterium Agrobacterium tumefaciens. Agrobacterium tumefaciens was found not to synthesize indole and to degrade it rapidly. The addition of exogenous indole dose-dependently inhibited A. tumefaciens growth and decreased its motility. Surprisingly, indole markedly increased A. tumefaciens biofilm formation on polystyrene, glass and nylon membrane surfaces and enhanced its antibiotic tolerance. Transcriptional analysis showed that indole markedly up-regulated several biofilm-related (celA, cheA, exoR, phoB, flgE, fliR and motA), stress-related genes (clpB, dnaK, gsp, gyrB, marR and soxR) and efflux genes (emrA, norM, and Atu2551) in A. tumefaciens, which partially explained the increased biofilm formation and antibiotic tolerance. In contrast, the plant auxin indole-3-acetic acid did not affect biofilm formation, antibiotic tolerance or gene expression. Interestingly, indole was found to exhibit several similarities with antibiotics, as it inhibited the growth of non-indole-producing bacteria, whereas these bacteria countered its effects by rapidly degrading indole, and by enhancing biofilm formation and antibiotic tolerance.
authors.affiliation: School of Chemical Engineering, Yeungnam University, Gyeongsan, 712-749, Korea.
authors.forename: Jin-Hyung
authors.initials: JH
authors.lastname: Lee
authors.forename: Yong-Guy
authors.initials: YG
authors.lastname: Kim
authors.forename: Kwang-Hyun
authors.initials: KH
authors.lastname: Baek
authors.forename: Moo Hwan
authors.initials: MH
authors.lastname: Cho
authors.forename: Jintae
authors.initials: J
authors.lastname: Lee
mesh_terms: D016960:Agrobacterium tumefaciens / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D001692:Biological Transport; D024881:Drug Resistance, Bacterial; D015964:Gene Expression Regulation, Bacterial; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D007211:Indoles / Q000378:metabolism* / Q000494:pharmacology; D010944:Plants / Q000382:microbiology; D015398:Signal Transduction; D013499:Surface Properties
chemical_list: D007210:Indoleacetic Acids; D007211:Indoles; C030737:indoleacetic acid; C030374:indole