title: Indole-Induced Activities of β-Lactamase and Efflux Pump Confer Ampicillin Resistance inPseudomonas putidaKT2440.
abstract: Indole, which is widespread in microbial communities, has received attention because of its effects on bacterial physiology.Pseudomonas putidaandPseudomonas aeruginosacan acquire ampicillin (Amp) resistance during growth on indole-Amp agar. Transcriptome, mutant, and inhibitor studies have suggested that Amp resistance induced by indole can be attributed to increased gene expression ofttgABencoding two genes of RND-type multidrug efflux operons and anampCencoding β-lactamase. Expression, enzyme activities, and mutational analyses indicated that AmpC β-lactamase is important for acquiring Amp resistance ofP. putidain the presence of indole. Here, we show, for the first time, that volatile indole increased Amp-resistant cells. Consistent with results of the volatile indole assay, a low concentration of indole in liquid culture promoted growth initially, but led to mutagenesis after indole was depleted, which could not be observed at high indole concentrations. Interestingly,ttgABandampCgene expression levels correlate with the concentration of indole, which might explain the low number of Amp-mutated cells in high indole concentrations. The expression levels of genes involved in mutagenesis, namelyrpoS,recA, andmutS, were also modulated by indole. Our data indicates that indole reduces Amp-induced heterogeneity by promoting expression of TtgABC or MexAB-OprM efflux pumps and the indole-induced β-lactamase inP. putidaandP. aeruginosa.
authors.affiliation: Laboratory of Molecular Environmental Microbiology, Department of Environmental Science and Ecological Engineering, Korea University, Seoul Korea.
authors.forename: Jisun
authors.initials: J
authors.lastname: Kim
authors.affiliation: Laboratory of Molecular Environmental Microbiology, Department of Environmental Science and Ecological Engineering, Korea University, Seoul Korea.
authors.forename: Bora
authors.initials: B
authors.lastname: Shin
authors.affiliation: Laboratory of Molecular Environmental Microbiology, Department of Environmental Science and Ecological Engineering, Korea University, Seoul Korea.
authors.forename: Chulwoo
authors.initials: C
authors.lastname: Park
authors.affiliation: Laboratory of Molecular Environmental Microbiology, Department of Environmental Science and Ecological Engineering, Korea University, Seoul Korea.
authors.forename: Woojun
authors.initials: W
authors.lastname: Park
keywords: Pseudomonas; ampicillin; antibiotics; bacteria; efflux pump; indole; resistance