Redox reactions in hydrocortisone transformation by Arthrobacter globiformis cells.

Hydrocortisone and prednisolone transformation by Arthrobacter globiformis cells in aerobic and anaerobic conditions was studied. 3-Ketosteroid-1-en-dehydrogenase activity was shown to be the major factor regulating the direction of transformation. When it is high (aerobic conditions), the end products of hydrocortisone transformation are prednisolone or its 20 beta-hydroxy derivative. The latter is produced via 1-en-dehydrogenation, which is not a limiting stage of the process. Low 3-ketosteroid-1-en-dehydrogenase activity (in the presence of cyanide) or its complete inhibition (strictly anaerobic conditions) result in the direct reduction of 20-keto group of hydrocortisone.

Regulation of 3-ketosteroid-1-en-dehydrogenase activity of Arthrobacter globiformis cells by a respiratory chain.

It has been shown that 3-ketosteroid-1-en-dehydrogenase localized in a cytoplasmic membrane donates reducing equivalents to a respiratory chain directly which passes them over to oxygen. Microbial hydrocortisone oxidation is coupled with energy generation in the form of the H+ transmembrane potential. Electron transfer via a respiratory chain is the limiting stage in the process of hydrocortisone 1-en-dehydrogenation.

Degradation of DDT and its analogs by Pseudomonas aeruginosa 640x.

The possibility of complete degradation of DDT by Pseudomonas aeruginosa 640x was demonstrated in principle. A study of the conditions of degradation of DDT by this culture was made. It was demonstrated that only dechlorination of DDT to DDD is accomplished without addition of a supplementary substrate. The rest of the processes right up to the formation of benzhydrol and phenylacetic acid take place only under conditions of cometabolism. For dechlorination of the aliphatic fragment of DDT and the aromatic rings, anaerobic conditions, nitrates in the form of electron acceptors, and calcium lactate as a cosubstrate are preferred. Degradation of nonchlorinated benzophenone takes place only under aerobic conditions with glycerol as a cosubstrate. Phenylacetic acid and benzhydrol are used by the culture as sole sources of carbon; aerobic conditions are necessary for their degradation. On the basis of analysis of decomposition products of DDT and a study of the pathways of degradation of its metabolites and analogs, a means of converting DDT by P. aeruginosa 640x is proposed.

Nature of transformation of hydrocortisone by cells incorporated into polyacrylamide gel.

The ability of Mycobacterium globiforme 193 cells immobilized in polyacrylamide gel (Paag) to transform soluble and microcrystalline hydrocortisone was investigated under conditions to periodic aeration. It was found that the specific 3-oxosteroid-delta'-dehydrogenase activity of immobilized cells hardly differs from that of free cells and averages 0.06 mumole/mg cells . min; the quantitative and qualitative composition of the transformation products formed by free and immobilized cells was identical. The linear relation between the accumulation of the reaction product, prednisolone, and the transformation time, the absence of an activating effect of SAA [surface-active agents] on the 3-oxosteroid-delta'-dehydrogenase activity, the correlation between enzymatic activity and viability, and the absence of an increase in activity during repeated transformations indicate that the cytoplasmic membrane of Myc. globiforme is not a significant diffusion barrier for the reaction substrate and product. Maintenance of immobilized cells in a viable state is a necessary condition of the retention of enzymatic activity by these cells. "Activation" of immobilized cells is achieved by incubating the granules in nutrient medium. The cause of the "activation," in our opinion, is the appearance of a new surface and, probably, internal cell population.

Decomposition of DDT and its analogs by soil microflora.

A search was made for active cultures that break down DDT. More than 600 microorganisms were isolated from soils treated for a long time with DDT and from accumulating cultures with DDT or its analogs as the carbon source and with DDT or its analogs and supplementary carbon sources. Cultures capable of degrading DDT under conditions of cometabolism were found among them. It was shown that the dechlorination of the trichloromethyl group of DDT was accomplished by a large number of microorganisms and occurred primarily under conditions of limited aeration. The elimination of chloride ions from the aromatic rings occurred only in the presence of cosubstrates under aerobic conditions and only with two strains. The strain Nocardia sp. 306x carried out complete degradation of DDT with the formation of DBH, DCBP, and an as yet unidentified entirely dechlorinated product. The most profound decomposition of DDT was produced by a culture of Ps. aeruginosa 640x, which entirely degraded the DDT molecule with the formation of phenylacetic acid.