Sorption of a Xenobiotic Contaminant in Clean and Petroleum-Contaminated Soil: Roles of Water and Xenobiotic Size

Environmental Context.Soil uptake of xenobiotics (e.g. pesticides) can be a complex phenomenon where it is useful to distinguish readily reversible sorption from longer-term retention. A scheme for doing this using fluorescence detection is presented here, along with application to uptake of a model compound in clean and oil-contaminated soils. Both the wetting of the soil and the size of the xenobiotic seem to be important. The present data concern uptake. Desorption is expected to exhibit dependencies on similar factors. The data have implications for understanding persistence. Abstract.Description of sorption of xenobiotics (e.g. pesticides) into soils requires identification of at least two kinetic components. In the present work, the distinction between ‘labile’ (readily reversible) and ‘non-labile’ (not reversible) uptake was extended, introducing a fluorescence-based method using 9-anthracenepropionic acid as a probe molecule. Study of clean, oil-contaminated wettable, and water-repellent oil-contaminated soils has given new perspectives into the role that water plays in xenobiotic uptake. Non-labile uptake is unimportant in the water-repellent soils; however, non-labile components are observed in both clean and wettable oil-contaminated samples, supporting earlier suggestions that water plays a role in non-labile uptake processes. A soil pre-exposed to water exhibited different labile sorption behavior from one where xenobiotic was added simultaneously with water to an air-dried soil. The comparatively rapid non-labile component of uptake (3 days) of 9-anthracenepropanoic acid by a clean soil contrasted with much longer times in earlier studies of 2,4-D and atrazine. This pointed to another factor influencing the sorption phenomenon. Literature data supports a suggestion that the non-labile component of xenobiotic sorption may be more strongly influenced by the size of the xenobiotic than by the structure (e.g. polarity) of the xenobiotic or soil composition.

Coaggregation of Candida dubliniensiswith Fusobacterium nucleatum

The binding of microorganisms to each other and oral surfaces contributes to the progression of microbial infections in the oral cavity. Candida dubliniensis, a newly characterized species, has been identified in human immunodeficiency virus-seropositive patients and other immunocompromised individuals.C. dubliniensis phenotypically resembles Candida albicans in many respects yet can be identified and differentiated as a unique Candida species by phenotypic and genetic profiles. The purpose of this study was to determine oral coaggregation (CoAg) partners of C. dubliniensis and to compare these findings with CoAg of C. albicansunder the same environmental conditions. Fifteen isolates ofC. dubliniensis and 40 isolates of C. albicans were tested for their ability to coaggregate with strains of Fusobacterium nucleatum,Peptostreptococcus micros, Peptostreptococcus magnus, Peptostreptococcus anaerobius,Porphyromonas gingivalis, and Prevotella intermedia. When C. dubliniensis andC. albicans strains were grown at 37°C on Sabouraud dextrose agar, only C. dubliniensis strains coaggregated with F. nucleatum ATCC 49256 and noC. albicans strains showed CoAg. However, when theC. dubliniensis and C. albicansstrains were grown at 25 or 45°C, both C. dubliniensis and C. albicans strains demonstrated CoAg with F. nucleatum. Heating theC. albicans strains (grown at 37°C) at 85°C for 30 min or treating them with dithiothreitol allowed the C. albicans strains grown at 37°C to coaggregate withF. nucleatum. CoAg at all growth temperatures was inhibited by mannose and α-methyl mannoside but not by EDTA or arginine. The CoAg reaction between F. nucleatum and the Candida species involved a heat-labile component onF. nucleatum and a mannan-containing heat-stable receptor on the Candida species. The CoAg reactions betweenF. nucleatum and the Candida species may be important in the colonization of the yeast in the oral cavity, and the CoAg of C. dubliniensis by F. nucleatum when grown at 37°C provides a rapid, specific, and inexpensive means to differentiate C. dubliniensisfrom C. albicans isolates in the clinical laboratory.

Influence of autoclaved or irradiated Aspergillus oryzae fermentation extract on fermentation in the rumen simulation technique (Rusitec)

SUMMARYA rumen simulation device (Rusitec) was used to compare the effects of autoclaved and γ-irradiated Aspergillus oryzae fermentation extract (AO) with those of untreated AO on rumen fermentation. Each vessel received daily 18 g of a basal diet consisting of 500 g hay, 299·5 g rolled barley, 100 g molasses, 91 g fishmeal and 9·5 g of a minerals and vitamins mixture/kg dry matter. AO preparations (0·25 g/day) were added with the feed. Dry matter digestion increased at 24 h, but not at 48 h, after adding AO, suggesting that AO stimulated the rate of digestion but not the extent. AO increased the numbers of total and cellulolytic bacteria by 90 and 50%, respectively. Irradiated AO stimulated numbers of bacteria in the same way as AO, although to a slightly lesser extent. Autoclaved AO had no effect. Thus, the mode of action of AO on rumen fermentation depends on a heat-labile component, possibly a nutrient or an enzyme, or metabolic activity. Viable AO cells are not required to stimulate bacterial growth and activity.

Effect of ovarian steroids on membrane ATPase activities in microsomes (microsomal fractions) from rat myometrium. Inhibition of a component of the Mg2+-activated ATPase by Ca2+-calmodulin and by oxytocin

The activities of Mg2+-ATPase (Mg2+-activated ATPase), (Ca2+ + Mg2+)-activated ATPase and (Na+ + K+)-activated ATPase have been determined in microsomes (microsomal fractions) obtained from rat myometrium under different hormonal conditions. Animals were either ovariectomized and treated for a prolonged period of time with 17 beta-oestradiol or progesterone, or myometria were obtained at day 21 of pregnancy. In each case the endometrium was carefully removed. The Mg2+-ATPase consists of two components: an inactivating labile component and a second constant component. The rate of ATP hydrolysis by the labile component of the Mg2+-ATPase declines exponentially as a function of time after adding the membranes to the assay medium; this inactivation is caused by the presence of ATP in the medium. This ATPase activity inhibited by ATP is catalysed by a labile enzyme and hence it gradually diminishes within a few hours, even when the microsomes are kept on ice. This labile component has the highest activity in microsomes from pregnant rats, a lower activity in progesterone-treated rats, and the lowest in 17 beta-oestradiol-treated rats. This component of the Mg2+-ATPase is not affected by 90 nM-oxytocin. The constant component of the Mg2+-ATPase must be ascribed to a different enzyme, which, in contrast with the labile component, is very stable and not affected by the hormonal status of the animal. This constant component of the Mg2+-ATPase is inhibited both by Ca2+-calmodulin, and by oxytocin in microsomes from pregnant and from progesterone-treated animals, whereas such inhibition does not occur in microsomes from 17 beta-oestradiol-treated animals. The activity of the (Na+ + K+)-activated ATPase is not dependent on the hormonal status of the animal. Myometrial microsomes present an ATP-dependent Ca2+ transport, irrespective of the hormonal condition, but only in microsomes obtained from rats treated with 17 beta-oestradiol, can a (Ca2+ + Mg2+)-activated ATPase activity be demonstrated. This activity can be stimulated by calmodulin.