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A F Pozharskii - One of the best experts on this subject based on the ideXlab platform.

Eugene L. Madsen - One of the best experts on this subject based on the ideXlab platform.

  • Naphthalene metabolism and growth inhibition by naphthalene in Polaromonas naphthalenivorans strain CJ2
    Microbiology, 2007
    Co-Authors: Graham M. Pumphrey, Eugene L. Madsen

    This study was designed to characterize naphthalene metabolism in Polaromonas naphthalenivorans CJ2. Comparisons were completed using two archetypal naphthalene-degrading bacteria: Pseudomonas putida NCIB 9816-4 and Ralstonia sp. strain U2, representative of the catechol and gentisate pathways, respectively. Strain CJ2 carries naphthalene catabolic genes that are homologous to those in Ralstonia sp. strain U2. Here we show that strain CJ2 metabolizes naphthalene via gentisate using respirometry, metabolite detection by GC-MS and cell-free enzyme assays. Unlike P. putida NCIB 9816-4 or Ralstonia sp. strain U2, strain CJ2 did not grow in minimal medium saturated with naphthalene. Growth assays revealed that strain CJ2 is inhibited by naphthalene concentrations of 78 μM (10 p.p.m.) and higher, and the inhibition of growth is accompanied by the accumulation of orange-coloured, putative naphthalene metabolites in the culture medium. Loss of cell viability coincided with the appearance of the coloured metabolites, and analysis by HPLC suggested that the accumulated metabolites were 1,2-naphthoquinone and its unstable auto-oxidation products. The naphthoquinone breakdown products accumulated in inhibited, but not uninhibited, cultures of strain CJ2. Furthermore, naphthalene itself was shown to directly inhibit growth of a regulatory mutant of strain CJ2 that is unable to metabolize naphthalene. These results suggest that, despite being able to use naphthalene as a carbon and energy source, strain CJ2 must balance naphthalene utilization against two types of toxicity.

  • Survival of naphthalene-degrading Pseudomonas putida NCIB 9816-4 in naphthalene-amended soils: toxicity of naphthalene and its metabolites
    Applied Microbiology and Biotechnology, 2003
    Co-Authors: Woojun Park, Che Ok Jeon, H. Cadillo, Christopher M. Derito, Eugene L. Madsen

    Survival of naphthalene-degrading Pseudomonas putida NCIB 9816-4 was measured in nonsterile soil samples (coal tar-contaminated and pristine) with and without added crystalline naphthalene over a period of 21 days. A 2–3 log decrease in cfu occurred in the presence, but not absence, of added naphthalene. We used aqueous suspensions of crystalline naphthalene to explore potential mechanisms of its toxicity on the test bacterium under aerobic conditions. Measurements of dissolved naphthalene in medium indicated that uptake by P. putida NCIB 9816-4 maintained naphthalene at concentrations well below saturation. Accumulation of catechol was documented by high-performance liquid chromatography and gas chromatography/mass spectrometry in the presence of 0.5% (w/v) naphthalene crystals. Transient catechol accumulation was highest when cells entered stationary phase. A decrease in catechol concentration correlated with the development of brown color in the medium. Brown pigment accumulation correlated with a decrease in viable cell counts. These results suggested that catechol, related compounds, and their condensation products can accumulate to toxic levels in stationary phase P. putida NCIB 9816-4 cells. We hypothesize that the same mechanism of toxicity may occur under the nutrient-limited conditions expected in soil.

  • Naphthalene and Donor Cell Density Influence Field Conjugation of Naphthalene Catabolism Plasmids
    Applied and Environmental Microbiology, 2000
    Co-Authors: A. M. Hohnstock, K. G. Stuart-keil, E. E. Kull, Eugene L. Madsen

    We examined transfer of naphthalene-catabolic genes from donor microorganisms native to a contaminated site to site-derived, rifampin-resistant recipient bacteria unable to grow on naphthalene. Horizontal gene transfer (HGT) was demonstrated in filter matings using groundwater microorganisms as donors. Two distinct but similar plasmid types, closely related to pDTG1, were retrieved. In laboratory-incubated sediment matings, the addition of naphthalene stimulated HGT. However, recipient bacteria deployed in recoverable vessels in the field site (in situ) did not retrieve plasmids from native donors. Only when plasmid-containing donor cells and naphthalene were added to the in situ mating experiments did HGT occur.

Alexander S Antonov - One of the best experts on this subject based on the ideXlab platform.

Vladimir Y Mikshiev - One of the best experts on this subject based on the ideXlab platform.

R. Symons - One of the best experts on this subject based on the ideXlab platform.

  • Polycyclic aromatic hydrocarbons in fuel-oil contaminated soils, Antarctica
    Chemosphere, 1999
    Co-Authors: Jackie Aislabie, Megan Balks, Norma Astori, Gavin Stevenson, R. Symons

    Where fuel oil spills have occurred on Antarctic soils polycyclic aromatic hydrocarbons (PAH) may accumulate. Surface and subsurface soil samples were collected from fuel spill sites up to 30 years old, and from nearby control sites, and analysed for the 16 PAHs on the USEPA priority pollutants list, as well as for two methyl substituted Naphthalenes, 1-methylnaphthalene and 2-methylnaphthalene. PAH levels ranged from 41-8105 ng g-1 of dried soil in the samples from contaminated sites and were below detection limits in control site samples. PAH were detected in surface soils and had migrated to lower depths in the contaminated soil. The predominant PAH detected were naphthalene and its methyl derivatives.