Polyphysa peniculus was grown in artificial seawater in the presence of arsenate, arsenite, monomethylarsonate and dimethylarsinic acid. The separation and identification of some of the arsenic species produced in the cells as well as in the growth medium were achieved by using hydride generation-gas chromatography-atomic absorption spectrometry methodology. Arsenite and dimethylarsinate were detected following incubation with arsenate. When the alga was treated with arsenite, dimethylarsinate was the major metabolite in the cells and in the growth medium; trace amounts of monomethylarsonate were also detected in the cells. With monomethylarsonate as a substrate, the metabolite is dimethylarsinate. Polyphysa peniculus did not metabolize dimethylarsinic acid when it was used as a substrate. Significant amounts of more complex arsenic species, such as arsenosugars, were not observed in the cells or medium on the evidence of flow injection-microwave digestion-hydride generation-atomic absorption spectrometry methodology. Transfer of the exposed cells to fresh medium caused release of most cell-associated arsenicals to the surrounding environment.

The separation and identification of some of the arsenic species produced in cells present in the growth medium when the microorganisms Apiotrichum humicola (previously known as Candida humicola) and Scopulariopsis brevicaulis were grown in the presence of arsenicals were achieved by using hydride generation-gas chromatography-atomic absorption spectrometry methodology (HG GC AA). Arsenite, monomethylarsonate, dimethylarsinate and trimethylarsine oxide were detected following incubation with arsenate. With arsenite as a substrate, the metabolites were monomethylarsonate, dimethylarsinate and trimethylarsine oxide; monomethylarsonate afforded dimethylarsinate and trimethylarsine oxide, and dimethylarsinate afforded trimethylarsine oxide. Trimethylarsine was not detected when the arsenic concentration was 1 ppm.

No abstract

Anaerobic enrichment cultures, isolated from arsenic-contaminated lake sediment in the Canadian sub-arctic and grown in five selective media, methylated arsenatef arsenite to produce mono-, di-and tri-methyl arsenicals. The extent of methylation and methylarsenic species produced varied with the type of enrichment. Iron-reducing, manganese-reducing, sulfate-reducing and broadspectrum anaerobic heterotrophic mixed cultures all produced methylarsenicals. Sulfate-reducing cultures produced higher concentrations of methylarsenicals (especially trimethyl species) than ironor manganese-reducers. There is evidence that several of the methylarsenicals, which were hydride-reactive at pH 6, were methylarsenic(II1) thiols. The organoarsenicals produced by enrichment cultures were the same as those detected in the porewater of the lake sediments used to initiate the enrichment cultures. Overall, this study demonstrates that microbes from anaerobic lake sediments can methylate (and demethylate) arsenic, a capability shared by manganese-, iron-, and sulfate-reducing microbial consortia.

. Can. J. Chem. 59,2677Chem. 59, (1981. Plant tissue cultures of Tripterygium wilfordii Hook F produced the cytotoxic diterpene triepoxides tripdiolide (1) and triptolide (2) in yields that were 16 and 3 times greater, respectively, than those observed in the plant itself. Other diterpenes, dehydroabietic acid (3) and 15-hydroxy-18-norabieta-3,8,11,13-tetraene-3-oic acid methyl ester (4) were also isolated. Co-occuring in these cultures were the cytotoxic quinone-methides, celastrol(5), compound 6, and compound 7. Other triterpenes produced were oleanolic acid (8) and polpunonic acid (9). p-Sitosterol(17) was also isolated. The proposed structure of 4 was confirmed by synthesis startingfrom compound 3. Cytotoxic data are reported, and a possible biosynthetic relationship among dehydroabietic acid, compound 4, and tripdiolide (1) is presented.