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Biomedical subjects

W Ahlf

Publications and source records attributed to W Ahlf.

6 recordsLinked to original sources
PubMed2002

A marine bioassay test set to assess marine water and sediment quality-its need, the approach and first results.

There is a need for establishing a marine bioassay test set to assess marine water and sediment samples in Germany. The selected marine bioassay test set, two tests for the water phase (with the luminescence bacteria Vibrio fischeri and the algae Phaeodactylum tricornutum Bohlin) and a whole sediment test with the marine amphipod Corophium volutator (Pallas) is described and first results are shown.

Amphipoda↗
PubMed2001

Effect of zinc and benzalkonium chloride on Nitrosomonas communis and potential nitrification in soil.

A bacterial contact assay is described which uses a chemoautotrophic microorganism, Nitrosomonas communis (strain Nm2) to evaluate the biological effect of contaminated soils. The effects of two toxicants on the ammonium oxidation activity of the autochthonous microbial population in the soil are compared with inhibition of the same biological response in the new monospecies bioassay. Experiments were performed using soil samples dosed with organic and inorganic contaminants (benzalkonium chloride and zinc) to demonstrate the mode of operation and the sensitivity of the bioassay. The EC50 values of zinc and benzalkonium chloride were calculated to be 171 and 221 mg kg-1 soil, respectively. The toxic response provided by the bioassay can thus predict the effect of soil pollutants on the autochthonous nitrifying bacteria.

Biological Assay↗
PubMed1998

Asking for the indicator function of bioassays evaluating soil contamination: are bioassay results reasonable surrogates of effects on soil microflora?

In evaluating the biological effect of solid materials like soil a bacterial contact assay often shows higher sensitivity than elutriate testing. Results of the Bacillus cereus contact assay for some environmental important toxicants are presented in this article. A comparison with another heterotrophic soil bacterium, Arthrobacter globiformis, shows comparable sensitivity. In a bioassay approach organisms at the level of individuals or populations are exposed to soil material to determine the significance of contaminants. An investigation that incorporates community level processes in comparison with toxicity test results provides a better understanding of the indicator function of bioassays. Comparison of soil bioassays (aqueous and solid phase) with ecological parameters demonstrates the problems in predicting ecological effects of soil contamination.

Arthrobacter↗
PubMed1997

Evidence from whole-sediment, porewater, and elutriate testing in toxicity assessment of contaminated sediments.

Bioassays with microorganisms are widely used as tools in estimating the potential risk of contaminated sediments. Although whole-sediment testing seems the most realistic approach to evaluate the bioavailability of contaminants in sediments, porewaters and aqueous extracts are frequently used. The object of this study was to compare whole sediment, porewater, and elutriate exposure of contaminated sediment simultaneously with two bacterial bioassays. Artificial sediment was spiked with five chemicals of different chemical and physical properties as single substances and as a mixture of all substances. Depending on the quality of the toxicants the test organisms were affected via aqueous phase (elutriate or porewater) or via solid phase (whole sediment). Sediment quality criteria based on the distribution of chemicals between sediment and aqueous phase and assessment of the toxicity of a sediment with water quality criteria were not confirmed by this study. The DHA solid-phase assay illustrated that threshold concentrations based on the NOEC values of single chemicals are not always sufficient to assess the risk of polluted sediments for organisms. It is suggested that for the evaluation of the potential hazard of a sediment contaminated with an unknown mixture of chemicals all exposure routes of contaminants should be examined by elutriate, porewater, and whole-sediment testing.

Bacillus cereus↗
PubMed1995

Microbial bioassays to assess the toxicity of solid-associated contaminants.

Due to the effects that sediment or soil matrices have on the bioavailability of compounds, it has been difficult to screen toxicity of solid-associated contaminants. The majority of microbial assays for testing toxicity of soils and sediments have been performed on water or solvent extracts. These procedures lead to a fractionation of the toxicity, which may underestimate or overestimate exposure routes and consequently potential adverse environmental effects. Recently, a solid-phase Microtox assay which eliminates the need for soil extracts and utilizes whole sediments or soils has been developed. This report describes a toxicity testing procedure using the inhibition of dehydrogenase enzyme activity of Bacillus cereus as test parameter. Studies with soil samples and a synthetic sediment spiked with organic contaminants and copper indicate the higher sensitivity of both solid-phase bioassays compared to water extract testing. A comparison of the results demonstrates that the B. cereus contact test is more sensitive for copper than the Photobacterium phosphoreum solid-phase test.

Bacillus cereus↗