Identification of mutagens in freshwater sediments by the Ames‐fluctuation assay using nitroreductase and acetyltransferase overproducing test strains

Abstract

Extracts of sediments from an area of concern in the Elbe river basins (Spittelwasser creek) were analyzed with the Ames-fluctuation test and in parallel with gas chromatography/mass spectrometry for compound identification. The standard test strains TA 98 and TA 100 showed mutagenicity mainly in medium-polar fractions of the sediment extracts. PAHs contribute to the overall mutagenic potential of the sample. Especially, cyclopenta[c,d]pyrene that was previously not defined as a priority hazardous substance has to be considered as well. The addition of metabolically competent test strains, which overexpress nitroreductase and acetyltransferase (e.g., YG1041 and YG1042) to the test battery, increased significantly the sensitivity of the Ames test for medium polar to polar genotoxins. The increased mutagenicity that was found in these bacterial strains indicates the presence of nitroarenes and/or aromatic amines. In fact, a number of heterocyclic and nitrogen-substituted aromatic compounds were identified in the sediments of the Spittelwasser creek of which methyl parathion, 1-naphthylamine, and N-phenyl-2-naphthylamine are mutagenic.

Mutagenicity in Surface Waters: Synergistic Effects of Carboline Alkaloids and Aromatic Amines

“…Effect directed analysis (EDA) is a valuable tool to unveil the chemicals contributing to adverse effects of an environmental sample by integrating effect testing, fractionation and nontarget analysis of active fractions to identify the chemicals driving the observed effects. , Several EDA studies were successful in identifying compounds responsible for mutagenic effects in sediments. , Although in some cases a limited number of novel key toxicants with major contributions were found such as phenylbenzotriazoles (PBTAs) , or benzidine derivatives (5-nitro-DCB), the causes of mutagenicity remain largely inconclusive in many surface waters or wastewater effluents . This might be attributed to the lack of extensive spectral libraries for liquid chromatography–mass spectrometry (LC-MS) data and to the limited information on analytical data for a reliable compound identification.…”

Coupling High-Performance Thin-Layer Chromatography with Bacterial Genotoxicity Bioreporters

“…As stated above, the limited separation power of the thin layer chromatography might lead to an underestimation of the number of genotoxic compounds, especially in case of wastewater samples containing a very large number of chemicals. The fact that in many cases it was not possible to explain genotoxic effects sufficiently by analyzed target compounds , under lines the necessity to analyze biological effects in addition to chemical analysis, and to use this as a starting point for an effect directed analysis. The proposed method might be useful in this respect although its separation power has to be improved or to be combined with other separation techniques such as HPLC.…”

“…While an earlier attempt to perform the S9-activation directly on the surface of the HPTLC-plate was unsuccessful, this approach can nevertheless succeed using a different protocol. Alternatively, this might be achieved by the use of S9-mix in a preincubation step and/or the use of genetically modified bacterial cells overexpressing enzymes involved in the metabolism of xenobiotics, such as cytochrome dependent monooxigenases, nitroreductases, and O-acetyl-aminotransferases. , The presented method prepares the ground for strategies combining HPTLC, HPLC, and mass spectrometry to facilitate efficient approaches for EDA. , …”

Identification and quantification of methylated PAHs in sediment by two-dimensional gas chromatography/mass spectrometry

“…C1, C2, etc.). 4,9,19,22 This is a rough approach, in which it is assumed that the chromatographic response factor of all methylated homologues is the same. However, this assumption is not correct.…”