Products from microbial metabolism

As might be expected, bacteria have been isolated from the plants that prodnce flnoroacetate, and these include an unidentified Pseudomonas sp. (Goldman 1965), a strain of Burkholderia Pseudomonas) cepacia from Dichapetalum cymosum (Meyer et al. 1990), and a strain of Morax-ella sp. (Kawasaki et al. 1981). In addition, fluoroacetate is an unusual product of microbial metabolism ... 

The toxin may undergo microbial degradation either while it is free in soil solution or while it is adsorbed. This could destroy all or part of the toxin, and there is evidence that most of the natural organic chemical groups that contain allelopathic compounds can be metabolized by some microorganism. The possibility always exists, however, that the microbial degradation product from the metabolism of an active toxin will itself be an allelopathic chemical. 

Pernicious anaemia was a fatal disease first reported in 1880. It was not until 1926 that it was discovered that eating raw liver effected a remission. The active principle was later isolated and called vitamin B12 or cyanocobalamin. It was initially obtained from liver but during the 1960s it was noted that it could be obtained as a by-product of microbial metabolism (Table 25.2). Hydroxycobalamin is the form of choice for therapeutic use and can be derived either by chemical transformation of cyanocobalamin or directly as a fermentation product. 

Stromatolites and microbialites Stromatolites are "laminated lithified sedimentary growth structures that form by accretion, through the addition of new laminae away from the point or surface of accretion." They normally are made up of carbonate minerals and thought to have formed in a shallow water environment. Modern freshwater stromatolites are made up of algal and cyanobacte-rial filaments. In the marine environment they form microbial mats and columns. These comparisons led many scientists to believe that stromatolites found in the ancient record are biogenic in origin and that they are in fact microbialites. That is, they are sedimentary structures in which minerals are precipitated as either a by-product of microbial metabolisms or as a by-product of microbial decay. 

For the foreseeable future, important new drug discoveries will be derived from products of microbial metabolism. If the full potentialities of this discovery source are to be realized, discovery processes will have to be refined and broadened in scope. These are some of the challenges and opportunities that I see for the decade ahead ... 

The phenmedipham and desmedipham taken up by plants are metabolised to essentially the same end-products as those from microbial metabolism in the soil (Kossmann, 1971). 

The formation of phosphine as a product of microbial metabolism is still enigmatic and cannot be associated so far with any defined microbial culture. Phosphine cannot be formed from phosphate by microbial activities to any significant amounts, but traces of phosphine may be formed through metabolic side reactions that have not been understood yet. One of the key sources of... 

The biofiltration process under recirculation conditions does not require additional equipment. The only need is to get a developed nontoxic porous surface in the filter bed and to saturate treated water with the oxygen of air to create required living conditions for aerobic microorganisms. But in any case, to maintain this fouling at acceptable levels, one need to effectively remove the products of microbial metabolism from the treated water. 

But the distinguished feature of the use of granular filter in conjunction with fiotator (bubble-fihn extractor) under recirculation conditions is the fact that the water is enriched with oxygen of air and then is fed continuously through the porous space of the filter material. And at the same time, the surface-active products of microbial metabolism are removed from that water flow due to the bubble-fihn extraction. 

All these natural products are known as secondary metabolites ( idiolites ). They are low molecular weight products of microbial metabolism (such as antibiotics, pheromones, sex hormones, etc.) that differ from primary metabolites (amino acids, vitamins, purines, pyrimidines, etc.) in that they are not involved in growth processes but rather in mechanisms of survival in nature. 

Soil microorganisms produce many compounds that are potentially toxic to higher plants. Examples include members of the following antibiotics (1-6), fatty and phenolic acids (7-12), amino compounds (13-15), and trichothecenes (16, 17). "Soil sickness" and "replant problems" have been reported where certain crops or their residues interfere with establishment of a subsequent crop (18, 19). Toxins resulting from microbial activity sometimes are involved, but it is often unclear whether these are synthesized de novo in microbial metabolism or are breakdown products of the litter itself (20). 

Hufford et al [57] used proton and 13C NMR spectrometric data to establish the novel sulfur-containing microbial metabolite of primaquine. Microbial metabolic studies of primaquine using Streptomyces roseochromogenus produced an A-acety-lated metabolite and a methylene-linked dimeric product, both of which have been previously reported, and a novel sulfur-containing microbial metabolite. The structure of the metabolite as an S-linked dimer was proposed on the basis of spectral and chemical data. The molecular formula C34H44N604S was established from field-desorption mass spectroscopy and analytical data. The 1H- and 13C NMR spectra data established that the novel metabolite was a symmetrical substituted dimer of primaquine A-acetate with a sulfur atom linking the two units at carbon 5. The metabolite is a mixture of stereoisomers, which can equilibrate in solution. This observation was confirmed by microbial synthesis of the metabolite from optically active primaquine. 

Microbial transformations of ellipticine (15) and 9-methoxyellipticine (16) were reported by Chien and Rosazza (143, 144). Of 211 cultures screened for their abilities to transform 9-methoxyellipticine (16), several, including Botrytis alii (NRRL 2502), Cunninghamella echinulata (NRRL 1386), C. echinulata (NRRL 3655), and Penicillium brevi-compactum (ATCC 10418), achieved O-demethylation of 16 in good yield (Scheme 9). P. brevi-compactum was used to prepare 9-hydroxyellipticine (22) from the methoxylated precursor, and 150 mg of product was obtained from 400 mg of starting material (37% yield). The structure of the metabolite was confirmed by direct comparison with authentic 9-hydroxyellipticine (143). O-Demethylation is a common microbial metabolic transformation with 16 and many other alkaloids (143). Meunier et al. have also demonstrated that peroxidases catalyze the O-demethylation reaction with 9-methoxyellipticine (145). 

Kamnev AA (1998) Reductive Solubilization of Fe(lII) by Certain Products of Plant and Microbial Metabolism as a Possible Alternative to Siderophore Secretion. Dokl Biophys 358-360, 48 (translation from Dokl Akad Nauk 359 691). 

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