Mixed bacterial cultures obtained from polychlorinated biphenyl-contaminated river sediments are capable of degrading monohalogenated biphenyls under simulated natural conditions. Culture conditions include river water as supportive medium and mixed bacterial cultures obtained from river sediments. Degradation occurs when the substrates are supplied as the sole carbon source or when added together with glucose. The degradation rates of 2-, 3-, and 4-chlorobiphenyl, at 30 jig ml-', were 1.1, 1.6, and 2.0 ,ug ml-' day-', respectively. Monobrominated biphenyls, including 2-, 3-, and 4-bromobiphenyl, were degraded at rates of 2.3, 4.2, and 1.4 ,ug ml-' day-', respectively. Metabolites, including halogenated benzoates, were detected by high-performance liquid chromatography and mass spectrometry. By using chlorophenyl ring-labeled monochlorobiphenyls as substrates, total mineralization (defined as CO2 production from the chlorophenyl ring) was observed for 4-chlorobiphenyl but not for 2-chlorobiphenyl. Rates of total mineralization of 4-chlorobiphenyl (at 39 to 385 ,ug ml-' levels) were dependent on substrate concentration, whereas variation of cell number in the range of 105 to 107 cells ml-1 had no significant effects. Simulated sunlight enhanced the rate of mineralization by ca. 400%. Polychlorinated biphenyls (PCBs) are ubiquitous anthropogenic pollutants (10, 13). Polybrominated biphenyls, although not as widespread

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It has been observed previously that the mutagenic action of nitrous acid may be potentiated by polyamines. We examined the cellular response of two deoxyribonucleic acid repair systems to treatment with spermidine-nitrite reaction products. uvrB- deficient mutants of Salmonella typhimurium LT2 showed enhanced lethal and mutagenic response to the reaction products. Lethal activity was further enhanced in a uvrB recA double mutant, whereas mutagenic activity was not detectable. Dependence of mutagenesis on the recA gene implicates the action of an error-prone repair system in the fixation of a premutagenic lesion as a mutation. From consideration of the substrate characteristics of the two repair systems studied, it is suggested that the deoxyribonucleic acid lesion formed by the reaction products of spermidine and nitrite is an intrastrand cross-link.

A multivariate approach was used to evaluate the significance of synthetic oilinduced perturbations in the functional activity of sediment microbial communities. Total viable cell densities, ATP-biomass, alkaline phosphatase and dehydrogenase activity, and mineralization rates of glucose, protein, oleic acid, starch, naphthalene, and phenanthrene were monitored on a periodic basis in microcosms and experimental ponds for 11 months, both before and after exposure to synthetic oil. All variables contributed to significant discrimination between sediment microbial responses in control communities and communities exposed to a gradient of synthetic oil contamination. At high synthetic oil concentrations (4,000 m/112 m3), a transient reduction in sediment ATP concentrations and increased rates of oleic acid mineralization were demonstrated within 1 week of exposure. These transient effects were followed within 1 month by a significant increase in rates of naphthalene and phenanthrene mineralization. After initial construction, both control and synthetic oil-exposed microbial communities demonstrated wide variability in community activity. All experimental microbial communities approached equilibrium and demonstrated good replication. However, synthetic oil perturbation was demonstrated by wide transient variability in community activity. This variability was primarily the result of the stimulation of polyaromatic hydrocarbon mineralization rates. In general, microcosms and pond communities demonstrated sufficient resiliency to recover from the effects of synthetic oil exposure within 3 months, although polyaromatic hydrocarbon mineralization rates remained significantly elevated.

To determine structural features necessary for the production of direct mutagenic activity from oligoamine-nitrate reaction mixtures, we systematically tested a group of aliphatic amine substrates for comutagenic action with nitrite. The ability to react with nitrite and form direct-acting mutagenic derivatives was common to a reasonably well defined class of aliphatic polyamines. In general, primary-secondary diamino compounds were mutagenic in the Ames Salmonella tester system when reacted with nitrite, whereas primary and secondary amines produced no direct mutagenic activity when tested separately. In combination with teritary amino groups, primary amines were inactive; one secondary-tertiary amine was tested, and this substrate produced mutagenic activity.