Microbiological analyses of sediments located near a point source for petrogenic chemicals resulted in the isolation of a pyrene-mineralizing bacterium. This isolate was identified as a Mycobacterium sp. on the basis of its cellular and colony morphology, gram-positive and strong acid-fast reactions, diagnostic biochemical tests, 66.6% G + C content of the DNA, and high-molecular-weight mycolic acids (C58 to C64). The mycobacterium mineralized pyrene when grown in a mineral salts medium supplemented with nutrients but was unable to utilize pyrene as a sole source of carbon and energy. The mycobacterium grew well at 24 and 30 degrees C and minimally at 35 degrees C. No growth was observed at 5 or 42 degrees C. The mycobacterium grew well at salt concentrations up to 4%. Pyrene-induced Mycobacterium cultures mineralized 5% of the pyrene after 6 h and reached a maximum of 48% mineralization within 72 h. Treatment of induced and noninduced cultures with chloramphenicol showed that pyrene-degrading enzymes were inducible in this Mycobacterium sp. This bacterium could also mineralize other polycyclic aromatic hydrocarbons and alkyl- and nitro-substituted polycyclic aromatic hydrocarbons including naphthalene, phenanthrene, fluoranthene, 3-methylcholanthrene, 1-nitropyrene, and 6-nitrochrysene. This is the first report of a bacterium able to extensively mineralize pyrene and other polycyclic aromatic hydrocarbons containing four aromatic rings.

Microbial Metabolism ofPolycyclic Aromatic Hydrocarbons: Isolation andCharacterization ofa Pyrene-Degrading Bacterium

Microbial metabolism of polycyclic aromatic hydrocarbons: isolation and characterization of a pyrene-degrading bacterium.

Sediments are the sink for particle-sorbed contaminants in aquatic systems and can serve as a reservoir of toxic contaminants that continually threaten the health and viability of aquatic biota. This work is a comprehensive review of published studies that investigated the genotoxicity of sediments in rivers, lakes and marine habitats. The Salmonella mutagenicity test is the most frequently used assay and accounts for 41.1% of the available data. The Salmonella data revealed mutagenic potency values for sediment extracts (in revertants per gram dry weight) that spans over seven orders of magnitude from not detectable to highly potent (105 rev/g). Analyses of the Salmonella data (n = 510) showed significant differences between rural, urban/industrial, and heavily contaminated (e.g., dump) sites assessed using TA98 and TA100 with S9 activation. Additional analyses showed a significant positive correlation between Salmonella mutagenic potency (TA98 and TA100 with S9) and PAH contamination (r2 = 0.19–0.68). The second and third most commonly used assays for the analysis of sediments and sediment extracts are the SOS Chromotest (9.2%) and the Mutatox® assays (7.8%), respectively. These assays are frequently used for rapid initial screening of collected samples. A variety of other in vitro endpoints employing cultured fish and mammalian cells have been used to investigate sediment genotoxic activity. Endpoints investigated include sister chromatid exchange frequency, micronucleus frequency, chromosome aberration frequency, gene mutation at tk and hprt loci, unscheduled DNA synthesis, DNA adduct frequency, and DNA strand break frequency. More complex in vivo assays have documented a wide range of effects including neoplasms and preneoplastic lesions in fish and invertebrate exposed ex situ. Although costly and time consuming, these assays have provided definitive evidence linking sediment contamination and a variety of genotoxic and carcinogenic effects observed in situ.

The mutagenic hazards of aquatic sediments: a review.

The commercial production of aromatic amines and nitroaromatic hydrocarbons began in the middle 1800s following the synthesis of aniline and the aniline-based dyes, rosaniline and mauve. Thirty years later, Rehn (1895) noted an increased incidence of urinary bladder cancer in German dyestuff workers, which Leichtenstern (1898) suggested could be due to their exposure to naphthylamines. This initial report was rapidly followed by additional epidemiological studies until it became incontrovertible that exposure to 2-naphthylamine, benzidine, and 4-aminobiphenyl could lead to the induction of bladder cancer in humans (reviewed in Parkes and Evans 1984).

Metabolic Activation and DNA Adducts of Aromatic Amines and Nitroaromatic Hydrocarbons

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in the environment - A review.

The sediments of Nagara river and its bystreams were extracted with ether. The mutagenicities of the extracts were determined by the Ames test with Salmonella typhimurium TA100 with S9 mix. The extracts were fractionated on an activated silica-gel column with four kinds of organic solvent, namely iso-octane, iso-octane:benzene (1:1), benzene:ethyl acetate (1:1) and benzene:methanol (1:1). The highest mutagenicity was observed in the iso-octane-benzene fraction of Arata river by using TA100 with S9 mix. Chemical substances in this fraction were identified by GC-MS and GC, and several kinds of polycyclic aromatic hydrocarbons (PAH) were found. Several peaks were unidentified, but these PAH, especially benzo [b] fluoranthene and benzo [a] pyrene, may contribute substantially to the mutagenicity of this fraction.

Mutagenicity of Nagara River sediment

Mutagenic activity was observed in sediments of the Suimon River bed with and without S9 mix. The direct-acting mutagens in the sediment were investigated. The sediment was extracted with methanol and fractionated on a Silica gel column. The benzene fraction from the Silica gel column exhibited mutagenic activity without S9 mix in strain TA98, while it failed to show mutagenic activity in nitroreductase-deficient strain TA98NR. This observation led to the suspicion that nitro compounds were the direct-acting mutagens of these samples. The benzene fraction was treated by heptafluorobutyric anhydride (HFBA) and investigated with gas chromatography equipped with an electron capture detector (GC-ECD). 2-Nitrofluorene, 4,4′-dinitrobiphenyl, 2,7-dinitrofluorene and 1-nitropyrene were detected and measured quantitatively. The mutagenic activity of a mixture of these compounds was compared with that of the original fraction and the direct-acting mutagenicity of Suimon River sediment can be explained by these nitroarenes, especially 1-nitropyrene.

Kenji Kato

Papers

Mutagenicity of Nagara River sediment

Nitroarenes in Suimon River sediment.