Dataset Information

Indole-Induced Activities of ?-Lactamase and Efflux Pump Confer Ampicillin Resistance in Pseudomonas putida KT2440.

ABSTRACT: Indole, which is widespread in microbial communities, has received attention because of its effects on bacterial physiology. Pseudomonas putida and Pseudomonas aeruginosa can 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 of ttgAB encoding two genes of RND-type multidrug efflux operons and an ampC encoding ?-lactamase. Expression, enzyme activities, and mutational analyses indicated that AmpC ?-lactamase is important for acquiring Amp resistance of P. putida in 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, ttgAB and ampC gene 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, namely rpoS, recA, and mutS, 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 ?-lactamase in P. putida and P. aeruginosa.

SUBMITTER: Kim J

PROVIDER: S-EPMC5348495 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Publications

Indole-Induced Activities of β-Lactamase and Efflux Pump Confer Ampicillin Resistance in Pseudomonas putida KT2440.

Kim Jisun J Shin Bora B Park Chulwoo C Park Woojun W

Frontiers in microbiology 20170314

Indole, which is widespread in microbial communities, has received attention because of its effects on bacterial physiology. Pseudomonas putida and Pseudomonas aeruginosa can 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 of ttgAB encoding two genes of RND-type multidrug efflux operons and an ampC encod ...[more]

PMID: 28352264

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Project description:Tripartite efflux systems transport antimicrobial agents, toxic metabolites, and siderophores from Gram-negative cells into the environment. For example, the main siderophore pyoverdine of the soil bacterium Pseudomonas putida KT2440 is secreted into the environment via the PvdRT-OpmQ and MdtABC-OpmB systems. Here, we looked for efflux systems that might be involved in the secretion of pyoverdine in addition to the latter two systems. Screening of different efflux systems revealed that parX (encoding the periplasmic adapter protein of the ParXY system) is of particular importance for bacterial growth under iron limitation. Further analysis showed that the deletion of parX impairs the production and secretion of pyoverdine, causing the observed growth effect. The effects were dependent on the presence of other tripartite efflux systems and the conditions of iron limitation. The results suggest that ParXY not only plays a role in antibiotic resistance, as shown previously, but also influences the secretion of siderophores in a network of overlapping activities of different tripartite efflux systems.IMPORTANCEGram-negative bacteria from the Pseudomonas group are survivors in various environmental niches. For example, the bacteria secrete siderophores to capture ferric ions under deficiency conditions. Tripartite efflux systems are involved in the secretion of siderophores, which are also important for antibiotic resistance. For one of these efflux systems, the resistance-nodulation-cell division transporter ParXY from the model organism Pseudomonas putida KT2440, we show that it influences the secretion of the siderophore pyoverdine in addition to its already known involvement in antibiotic resistance. Phenotypically, its role in pyoverdine secretion is only apparent when other pyoverdine secretion systems are inactive. The results confirm that the different tripartite efflux systems have overlapping substrate specificities and can at least partially functionally substitute for each other, especially in important physiological activities such as supplying the cell with iron ions. This fact must be taken into account when developing specific inhibitors for tripartite efflux systems.

Project description:Resistance-nodulation-division (RND) transporters are involved in antibiotic resistance and have a broad substrate specificity. However, the physiological significance of these efflux pumps is not fully understood. Here, we have investigated the role of the RND system TtgABC in resistance to metal ion chelators in the soil bacterium Pseudomonas putida KT2440. We observed that the combined action of an RND inhibitor and the chelator 2,2'-bipyridyl inhibited bacterial growth. In addition, the deletion of ttgB made the strain susceptible to 2,2'-bipyridyl and natural bipyridyl derivatives such as caerulomycin A, indicating that TtgABC is required for detoxification of compounds of the bipyridyl family. Searching for the basis of growth inhibition by bipyridyls, we found reduced adenosine triphosphate (ATP) levels in the ttgB mutant compared to the wild type. Furthermore, the expression of genes related to iron acquisition and the synthesis of the siderophore pyoverdine were reduced in the mutant compared to the wild type. Investigating the possibility that 2,2'-bipyridyl in the ttgB mutant mediates iron accumulation in cells (which would cause the upregulation of genes involved in oxidative stress via the Fenton reaction), we measured the expression of genes coding for proteins involved in intracellular iron storage and the response to oxidative stress. However, none of the genes was significantly upregulated. In a further search for a possible link between 2,2'-bipyridyl and the observed phenotypes, we considered the possibility that the ion chelator limits the intracellular availability of metabolically important metal ions. In this context, we found that the addition of copper restores the growth of the ttgB mutant and the production of pyoverdine, suggesting a relationship between copper availability and iron acquisition. Taken together, the results suggest that detoxification of metal chelating compounds of the bipyridyl family produced by other bacteria or higher ordered organisms is one of the native functions of the RND efflux pump TtgABC. Without the efflux pump, these compounds may interfere with cell ion homeostasis with adverse effects on cell metabolism, including siderophore production. Finally, our results suggest that TtgABC is involved in resistance to bile salts and deoxycholate.

Dataset Information

Indole-Induced Activities of ?-Lactamase and Efflux Pump Confer Ampicillin Resistance in Pseudomonas putida KT2440.

Publications

Indole-Induced Activities of β-Lactamase and Efflux Pump Confer Ampicillin Resistance in <i>Pseudomonas putida</i> KT2440.

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