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A novel pathway of molinate mineralization promoted by a defined mixed culture composed of five bacteria (named ON1 to ON5) was proposed previously. Evidence was obtained of a metabolic association between Gulosibacter molinativorax ON[4.sup.T], capable of molinate breakdown, and the remaining bacteria. In the present study, the role of each isolate in that metabolic association was further explored and the possible synergistic effect of all the bacterial isolates for the stability of the mixed culture is discussed. The cleavage of the molinate thioester bond, whether occurring under aerobic or anaerobic conditions, releases ethanethiol (S-ethyl moiety) and an azepane moiety derivative, identified as azepane-1-carboxylic acid. This azepane moiety is degraded, in the presence of oxygen, by Pseudomonas strains ON1 and ON3 and G. molinativorax ON[4.sup.T]. Ethanethiol, which inhibits G. molinativorax ON[4.sup.T], is consumed by Pseudomonas strain ON1 and Stenotrophomonas maltophilia ON2. Although a two-member mixed culture of G. molinativorax ON[4.sup.T] and Pseudomonas strain ON1 was able to promote the aerobic mineralization of molinate, after 20 successive transfers of the five-member mixed culture in mineral medium with molinate, none of these isolates were lost. The results obtained indicate that the whole mixed culture may have a higher fitness than the two-member culture, even when the basic degradative and cross-protection functions are assured.

The sulfonylureas and imidazolinones are potent commercial herbicide families. They are among the most popular choices for farmers worldwide, because they are nontoxic to animals and highly selective. These herbicides inhibit branched-chain amino acid biosynthesis in plants by targeting acetohydroxyacid synthase (AHAS, EC 2.2.1.6). This report describes the 3D structure of Arabidopsis thaliana AHAS in complex with five sulfonylureas (to 2.5 A resolution) and with the imidazolinone, imazaquin (IQ; 2.8 A). Neither class of molecule has a structure that mimics the substrates for the enzyme, but both inhibit by blocking a channel through which access to the active site is gained. The sulfonylureas approach within 5 A of the catalytic center, which is the C2 atom of the cofactor thiamin diphosphate, whereas IQ is at least 7 [Angstrom] from this atom. Ten of the amino acid residues that bind the sulfonylureas also bind IQ. Six additional residues interact only with the sulfonylureas, whereas there are two residues that bind IQ but not the sulfonylureas. Thus, the two classes of inhibitor occupy partially overlapping sites but adopt different modes of binding. The increasing emergence of resistant weeds due to the appearance of mutations that interfere with the inhibition of AHAS is now a worldwide problem. The structures described here provide a rational molecular basis for understanding these mutations, thus allowing more sophisticated AHAS inhibitors to be developed. There is no previously described structure for any plant protein in complex with a commercial herbicide. inhibition | sulfonylurea | x-ray crystallography | imidazolinone | thiamin diphosphate

Research has been conducted on the s-triazine herbicides. Results indicate that these herbicides hydrolytically displace chloride and amino substituents of 2-chloro-4,6-diamino-s-triazine.

Research has been conducted on Ralstonia eutropha JMP134(pJP4) and other motile bacteria species which can degrade herbicide 2,4-dichlorophenoxyacetate. The hypothesis that R. eutropha can be chemotactically attracted to 2,4-dichlorophenoxyacetate has been tested and the results are reported.

Results show that the chloride channel inhibitor 5-nitro-2-(3-phenylpropylamino) benzoic acid) (NPPB) binds to the Q(sub)B binding site of photosystem II. Data indicate that the inhibitory activity of NPPB resembles that of arylaminobenzoate's inhibition of the mammalian chloride channels.

Only one herbicide is currently available for preemergence broad-leaf weed control in flue-cured tobacco (Nicotiana tabacum L.) grown in Canada. The high cost of registration, coupled with the small crop size, has resulted in few new products becoming available. Herbicide resistance introduced into tobacco by Agrobacterium-mediated transformation may allow the use of products with existing or impending registrations. We used two new, low-residual sulfonylurea herbicides: amidosulfuron (3-(4,6-dimethoxyprymidin-2-yl)-1-(N-methyl-N-methylsulfonyl-am inosulfonylurea) and DPX-R9674, which is a mixture of thifensulfuron (methyl-3-(((((N-4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino) carbonyl) amino) sulfonyl)-2-thiophenecarboxylate) and tribenuron (methyl 2((((N-4-methoxy-6-methyl-1,3,5-triazin-2-yl)methylamino) carbonyl) amino) sulfonyl) benzoate). These two and chlorsulfuron (2-chloro-N-((4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbon yl) benzenesulfonamide) were applied to two transgenic tobacco genotypes harboring the csr1-1 gene for chlorsulfuron resistance and compared with an untransformed control. Our purpose was to determine if transgenic seedlings were resistant to DPX-R9674 and amidosulfuron. The experiment was a factorial in a completely randomized design with 25 replications. The three herbicides were applied to the transgenic and control seedlings at three rates. The transgenic seedlings had significantly higher leaf area, top dry weight, and root dry weight than the untransformed control when sprayed with any of the three herbicides. Seedlings were highly resistant to amidosulfuron and chlorsulfuron. Resistance to DPX-R9674 in the transgenic seedlings was minimal, which was unexpected, considering that an analysis of AHAS activity revealed high levels of cross-resistance to chlorsulfuron, DPX-R9674, and amidosulfuron. It is possible that DPX-R9674 is metabolized into products that are herbicidally active at different AHAS binding sites. One of the transgenic lines was more resistant to herbicide application than the other indicating that selection for maximum gene expression among transgenic lines is a necessary part of transgenic cultivar development. It was concluded that DPX-R9674 would not be suitable for use with transgenic crops harboring the csr1-1 gene for chlorsulfuron resistance. The other low-residual sulfonylurea, amidosulfuron, was more promising.

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are contaminants found in many herbicides and in defoliants such as Agent Orange, used in Vietnam in the 1960s. These compounds are toxic and when ingested cause loss of appetite and weight, and liver damage. These compounds have also been reported to be teratogenic (causing birth defects). In order to evaluate the tissue distribution (where the chemical goes in the body after it is ingested) and whether these compounds can be transferred from a mother to the fetus, a pregnant marmoset monkey was injected with a mixture of PCDDs and PCDFs, 11 weeks prior to delivery (week 10 of pregnancy). Tissue samples from the mother, from the infant one day after birth, and from the infant following 33 days of breast feeding, were analyzed for the presence of PCDDs and PCDFs. One week after injection, the highest levels of these compounds were found in liver, adipose (fat) tissue, lungs and thymus of the mother. Very low levels were found in the heart, kidney and brain. Within 16 weeks of treatment, the tissue levels of some of the compounds were significantly reduced, while others remained high. In contrast to the mother, the one-day-old infant had the highest tissue levels of PCDDs and PCDFs in adipose tissue and had low levels in the liver. After 33 days of breast feeding the levels of these compounds in the infant's liver increased significantly. It is concluded that PCDDs and PCDFs are accumulated in the adult liver and fat tissues, are transferred across the placenta to the fetus, and are transferred from the mother to the infant through breast milk. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research has been conducted on the racemic indanofan. The conversion of this compound to the enantiopure (S)-indanofan has been carried out via the chemical inversion techniques the enzymatic resolution and the details are reported.