摘要:

AbstractThree single‐species bioassays (Microtox,Selenastrum capricornutum, andPanagrellus redivivus) and a test using microbial communities developed on artificial substrates were used in a series ofin situand laboratory tests evaluating the ecotoxicological hazard of contaminated sediments at two sites on Lake Michigan: Waukegan (Illinois) Harbor and The Chicago Area Confined Disposal Facility Study. In the single‐species tests, exposure to elutriates of contaminated sediments significantly inhibited bacterial luminescence, algal photosynthesis, and nematode survival and growth at polluted stations, while elutriates from control stations did not. The battery of three tests is a promising screening tool for in‐place pollutants.Protozoan species richness and protozoan phototroph abundance were inhibited by elutriates from contaminated sites, but the abundance of heterotrophic protozoans was enhanced by sediment elutriates from some stations. Microbial community photosynthesis was significantly inhibited by most sediment elutriates, while community respiration was often stimulated; thus, functional responses paralleled the structural changes. Overall, the results of the microbial community tests were consistent with expected patterns of toxicity at the two sites on Lake Michigan.In general, single‐species test results agreed with the community bioassays. Although community tests may be more realistic than single‐species bioassays in predicting the impact of sediment contamination on actual ecosystems, caution must be exercised in interpreting th

ISSN:0884-8181    

DOI:10.1002/tox.2540040103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractUntil recently, only three obligately aerobic bacteria (affiliated with the genusPseudo‐monas) that can grow with nitrilotriacetate (NTA) as their only source of carbon, nitrogen, and energy have been isolated and studied in pure culture. By employing a different isolation strategy than was used previously, several nonpseudomonads were isolated in pure culture from both soil and wastewater that are able to utilize NTA under aerobic growth conditions. Additionally, a denitrifying bacterium was isolated from river sediment that is able to utilize NTA in the absence of oxygen. These isolates have been characterized with respect to their cell morphology and physiology. The data collected so far do not allow classification of both the gram‐negative and the gram‐positive strains isolated, and the taxonomic position of the isolates remains obscure. However, properties like C1utilization, production of acetoïn, and nonmotility clearly indicate that the gram‐negative strains do not belong to the genusPseudomonas. Information is presented on the regulation of NTA‐metabolizing enzymes in isolate TE 1 suggesting that these enzymes are inducible in this

ISSN:0884-8181    

DOI:10.1002/tox.2540040104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of limiting nutrient to algal toxicity tests are discussed. It has been shown, through theoretical derivation, that EC50values will vary with changes of nutrient concentration even if the effects of limiting nutrient and limiting toxicant on algal growth are independent. The variation in EC50's is governed by the degree of correlation between two variables: the tolerance and the activation level. The proposed theory shows a potential application for making a comparison of results obtained from different laboratories or methods and for applying laboratory results to field conditions.

ISSN:0884-8181    

DOI:10.1002/tox.2540040105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe toxicity of some mycotoxins, lactones and dicarboxylic anhydrides, insecticides, herbicides, and fungicides can be detected by means of bacterial assays. In addition, the order of magnitude of the toxicity can also be evaluated.Fifty‐eight chemicals as well as extracts of peanuts, apple juices, and grains have been investigated in a test battery of three different kinds of assays. In cup plate diffusion assays a minimal amount of approximately 0. 1 mg/mL of mycotoxin may be detected by means of growth inhibition assays withBacillus thuringiensison one hand, and pigment synthesis inhibition assays with mutants ofSerratia marcescenson the other hand. Swarming inhibition assays with the motile strainsAzospirillum brasilenseandProteus mirabilisshow the same sensitivity. Comparisons of our test battery with other bioassays, as well as with mammalian toxicity tests (LD50values), reveal correlations between these kinds of assays in regard to the test substance

ISSN:0884-8181    

DOI:10.1002/tox.2540040106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe validity of the equation for first‐order kinetics and of the empirical equationc=c0‐kt1/2was checked against experimental data on the decomposition of the herbicides linuron and atrazine at different initial concentrationsc0, in soil. Standard statistical criteria showed acceptable fits to the data according to first‐order kinetics, but the more stringent criterion of independence of the first‐order rate constant onc0proved this kinetics to be invalid. The empirical equation gave a better fit to the data. Furthermore, the rate constantkvaried linearly withc0at lowc0and with c1/20at highc0. Similar relations betweenkandc0were also found with14C‐labeled linuron, when it was found that the curve describing the collected amount of14C in CO2consisted of more than one phase. The empirical equation can thus be used to assess quantitatively the influence of various factors on the degradation, using both unlabeled and14C‐labeled

ISSN:0884-8181    

DOI:10.1002/tox.2540040107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of genotoxic agents on DNA structure, repair, and mutation—induction have shown many clear effects and mechanisms, yet their action on cellular transposons and insertion elements has been less well examined. We are interested in addressing the effect of environmental insults on the induction of DNA transposition of a cell's complement of mobile genetic elements. We have previously described a model system whereby we can measure the transposition potential of a cell by fusing bacteriophage Mu's (a plaque‐forming viral transposon) transposase (A gene) to that encoding β‐galactosidase (lacZ) and assaying for changes in β‐galactosidase expression after exposure of cells to toxic agents. We found that a known DNA‐damaging agent, γ‐rays, appeared to exert no discernible effect on Mu DNA transposition or transposase gene expression. In addition to monitoring the consequences of simple extrinsic agents, however, we were also curious to see how complex environmental mutagens influence DNA transposition and transposase gene expression.To accomplish this, we studied Mu transposase gene expression after exposure ofE.colicells harboring the MuA′‐′lacZ fusion plasmid pMD12 to six different cigarette smoke condensates (CSC). Upon exposure to CSC alone, no apparent pattern of changes in Mu transposase expression was observed in eitherrecA+orrecA−strains. However, when the CSC were treated with an Aroclor 1254 activated liver microsomal fraction, there was a consistent dose‐dependent decrease in transposase expression inrecA+E.coli, but not in an otherwise isogenicrecA−strain. This result is specific for Mu transposase expression as control strains, containing thelacZ gene under its own regulatory circuitry rather than that of the Mu transposase gene, did not exhibit a striking positive or negative effect on β‐galactosidase e

ISSN:0884-8181    

DOI:10.1002/tox.2540040108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWe report the results of an experiment designed to study the effects of organic pollutants on microbial populations indigenous to subsurface soil. Subsurface soil from a pristine short grass prairie, collected aseptically and anaerobically, was used to construct microcosms. The microcosms were divided into three groups: control, biotic chemical, and abiotic chemical. The chemical groups received additions of three organic pollutants in varying concentrations: phenothiazine, chloronapthalene, and polychlorinated biphenyl. The microbial activity of the abiotic chemical group was inhibited with mercuric chloride. The control group received only water. Microbial activity was monitored in all groups using several enzyme assays and a biomass estimate: amylase, dehydrogenase, esterase, phosphatase, protease, and soil protein concentration. Eh and pH were also monitored. Throughout the 32 weeks, overall reducing conditions prevailed in the biotic chemical and control groups. The Eh of the abiotic group remained high. Significant differences were seen among groups in specific enzymatic activities on specific sample dates. However, fluctuating values through time due to succession of microbial consortia made it impossible to make predictions about the overall effects of the pollutants on individual activity measurements. This study is the first report of the effects of a mixture of organic pollutants on microbial consortia indigenous to subsurface soils.

ISSN:0884-8181    

DOI:10.1002/tox.2540040109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0884-8181    

DOI:10.1002/tox.2540040110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0884-8181    

DOI:10.1002/tox.2540040102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY