[Strain polymorphism of the plasmid profiles in Acidithiobacillus ferrooxidans]. / Shtammovyi polimorfizm plazmidnykh profilei u Acidithiobacillus ferrooxidans.

Plasmid profiles were studied in 27 Acidithiobacillus ferrooxidans strains isolated from different geographic zones and substrates differing in the composition of the main sulfide minerals, and also in experimentally obtained strains with acquired enhanced resistance to the ions of heavy metals (Fe, Ni, Cu, Zn, As). In 16 out of 20 strains isolated from different substrates, one to four 2- to 20-kb and larger plasmids were revealed. Plasmids were found in all five strains isolated from gold-containing pyrite-arsenopyrite ores and concentrates, in nine of 11 strains isolated from the ores and concentrates containing nonferrous metals, and in two of four strains isolated from the oxidation substrates of simple composition (mine waters, pyritized coals, active sludge). Changes in the plasmid profiles in some A. ferrooxidans strains (TFZ, TFI-Fe, TFV-1-Cu) with experimentally enhanced resistance to Zn2+, Fe3+, and Cu2+, respectively, were noted as compared with the initial strains. After 30 passages on S0-containing medium, strain TFBk showed changes in the copy number of plasmids. The role of plasmids in the processes of oxidation of energy substrates and in the acquired enhanced resistance to the heavy metal ions is discussed.

[Decomposition of human blood cholesterol by the enzyme from Actinomyces lavendulae]. / Razlozhenie kholesterina, soderzhashchegosia v krovi cheloveka, fermentnym preparatom iz Actinomyces Lavendulae.

In vitro experiments with enzymic decomposition of cholesterol contained in the human blood were carried out. The enzyme was obtained from the mycelium of Actinomyces lavendulae. As a result of incubation of blood samples in the presence of the enzyme at 37 degrees, the cholesterol content decreased and reached 30--43% of the initial value within 2 hours. The enzyme showed its specific effect only upon free cholesterol but not on its esters.

[Alpha-ketoglutarate dehydrogenase activity of Candida lipolytica during alpha-ketoglutarate biosynthesis]. / Aktivnost' alpha-ketoglutaratdegidrogenazy u Candida lipolytica pri biosinteze alpha-ketoglutarata.

The activity of alpha-ketoglutarate dehydrogenase (KGDH) was assayed in cell-free yeast homogenates with respect to studying the mechanism of alpha-ketoglutarate (KG) overproduction by the thiamine-heterotrophic culture of Candida lipolytica in media with hexadecane. Two types of yeast cells were used for analysis: (1) cells grown in the conditions of thiamine excess (500 mcg/l) and taken at the logariphmic growth phase; (2) cells grown in the conditions of thiamine deficiency and taken at the beginning of KG overproduction when the cultural growth was limited by thiamine. The activity of KGDH was assayed in the absence of thiamine diphosphate (TDP) and in its presence, the content of the holoenzyme and the total content of the holoenzyme and the apoenzyme being determined respectively. The activity of holoKGDH in the thiamine-deficient cells of C. lipolytica producing KG was almost five times lower than in the cells grown in the conditions of thiamine excess. In the latter, all KGDH was in the form of the holoenzyme; in the thiamine-deficient cells, 90% of KDGH was in the form of the apoenzyme devoid of TDP and therefore lacking the enzyme activity. The total content of holoKGDH IN THE THIAMINE-DEFICIENt cells producing KG was twice as high as in the cells grown in the conditions of thiamine excess. The data obtained are discussed in relation with the mechanism of KG biosynthesis from n-alkanes by yeast cells.

[Pyruvate- and alpha-ketoglutarate dehydrogenase activity during yeast growth on glucose and hexadecane]. / Aktivnost' piruvat- i alpha-ketoglutaratdegidrogenazy pri roste drozhzhevykh organizmov na gliukoze i na geksadekane

The activity of pyruvate- and ketoglutarate dehydrogenases (PDH and KGDH) was determined in the cells of Candida lipolytica and Candida tropicalis during the exponential phase of their growth on glucose and hexadecane. The activity of PDH in the cells growing on hexadecane was found to be lower than in the cells growing on glucose. The activity of KGDH was almost the same in the cells cultivated on hexadecane and glucose. The results obtained are discussed with respect to different pathways of degradation of glucose and n-alkanes, and a decreased requirement in thiamine during growth of the yeast cells on n-alkanes.

[Activity of pentose phosphate pathway enzymes in alkane-oxidizing yeast cells]. / Aktivnost' fermentov pentozofosfatnogo tsikla v kletkakh alkanokisliaiushchikh drozhzhei

The activity of the key enzymes of the pentose phosphate pathway (glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, transketolase) was determined in cell-free homogenates of Candida lipolytica 695 and Candida tropicalis 303 growing on different carbon sources. The activity of these enzymes remained almost the same in the course of growth of both cultures. The activity of the enzymes differed only slightly in the cells metabolizing hexadecane and glucose. The activity of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in the cell-free homogenates of C. tropicalis 303 was twice as high as in the cells of C. lipolytica 695. The activity of transketolase was the same in both cultures. The main role of the pentose phosphate pathway is presumed to consist not in catabolism of the carbon source, but in biosynthesis of pentoses and other important intermediates.