The concentration dynamics of inorganic polyphosphates during the cephalosporin C synthesis by Acremonium chrysogenum

The contents of five fractions of energy-rich inorganic polyphosphates (polyPs), ATP, and H⁺-ATPase activity in the plasma membrane were determined in a low-activity cephalosporin C (cephC) producer Acremonium chrysogenum ATCC 11550 and selected highly efficient producer strain 26/8 grown on glucose or a synthetic medium providing for active synthesis of this antibiotic. It was shown that strain 26/8 on the synthetic medium produced 26-fold higher amount of cephC as compared with strain ATCC 11550. This was accompanied by a drastic decrease in the cell contents of ATP and the high-molecular-weight fractions polyP2, polyP3, and polyP5 with a concurrent increase in the low-molecular-weight fraction polyP1. These data suggest that polyPs are involved in the cephC synthesis as a source of energy. H⁺-ATPase activity insignificantly changed at both low and high levels of cephC production. This confirms the assumption that A. chrysogenum has other alternative antibiotic transporters in addition to cefT. The obtained results can be used for optimizing commercial-scale cephC biosynthesis.     

A study of steroid hydroxylation activity of Curvularia lunata mycelium

It has been demonstrated that the mycelium of Curvularia lunata at the end of the logarithmic growth phase displays a maximal 11-hydroxylase activity towards cortexolone (4-6 g/l) used for transformation as a microcrystalline suspension in phosphate buffer. The mycelium at a later stage of fungal growth displays an elevated 14-hydroxylase activity, necessary for generation of 14-hydroxyandrostenedione. The effects of different forms of substrate added to the reaction mixture, age and concentration of mycelium, and fungal clones tolerant to salts of heavy metals (0.35-0.5%) were studied to remove the side 14-hydroxylation, accompanying the main cortexolone transformation. Mycelia of the fungal clones tolerant to Co2+ and Cu2+ displayed a weak hydroxylase activity or its complete absence and an elevated content of melanin, the biosynthesis of which is intensified under adverse conditions. The results obtained suggest that the transformation of steroids by the studied C. lunata strain is a detoxication of foreign compounds.     

Sulfur containing acyclovir derivatives: synthesis, cytotoxic activity, and cell phenotype studies

New 2-amino-6-oxo-8-thioxo-9-substituted purine derivatives were prepared and assayed for the in vitro cytotoxic activity. Some products exhibited moderate activity on HT-1080 cells and rather high activity on MG-22A cells.     

Multiaberrant cells in groups of people exposed to radiation in different situations and their possible biological role

The results of the analysis of multiaberrant cells (MAC) obtained in the course of long-term investigation of cytogenetic effects in human peripheral blood lymphocytes are presented. MAC were discovered in different groups of people exposed to the radiation factor. No such cells were found in control groups. The greatest number of MAC “carriers” (37.5%) was registered among employees of radiochemical plants who had contacts with plutonium salts. The highest frequency of MAC (2.49 ± 0.59 per 1000 cells) was also revealed in the same group. It exceeded by an order of magnitude the values in other examined groups. In the groups of radiochemical workers, cosmonauts, and miners from Tselinograd the frequency of dicentrics and centric rings was also the highest as compared to that in other groups. The character of chromosome aberrations observed in MAC suggests that they are formed under the action of the radiation factor, and their frequency among different groups of people exposed to radiation makes it possible to assume that formation of MAC is a result of the action on lymphocytes of α-particles emitted by radionuclides incorporated in the organism. Classical MAC observed in routine studies (fluorescence plus Giemsa staining) are only an extreme manifestation of cell damage. To elucidate the true picture of chromosome rearrangements induced by radiation and the role of MAC in the tumor process, it is necessary to use the methodical potentialities of modern molecular cytogenetics, including the FISH method.     

Penicillin formation by biochemical mutants of Penicillium chrysogenum and their spontaneous revertants

The capacity for the antibiotic production in the auxotrophs of Penicillium chrysogenum with various deficiency and their revertants was studied. It was found that the capacity for penicillin synthesis was impaired to various degrees in the majority of the auxotrophs. Variants with the penicillin production levels by 13--20 per cent higher than those in the initial prototrophic strain were isolated for the first time in selection of the eukaryotes with the method of obtaining highly active revertants from auxotrophs according to the scheme "prototroph-auxotroph-prototroph".     

Mutagenic action of N-nitrosodimethylurea on Actinomyces rimosus and Penicillium chrysogenum]

High mutagenic activity of N-nitrozodimethylurea (NDMU), an agent of the group of the nitrozo compounds not studied in detail was shown with respect to prototrophic and auxotrophic strains of Actinomyces rimosus, an organism producing oxytetracycline and Penicillium chrysogenum, an organism producing penicillin. The rate of direct and back mutations in the auxotrophic strain of Act. rimosus under the effect of NDMU was many times higher than that of spontaneous mutations. NDMU was used at one of the selection stages at which a more active variant of Act. rimosus was obtained. This is evident of a possible use of the mutagen for induction of variation with respect to the quantitative feature of oxytetracycline production. A great number of morphologically changed forms and biochemical mutants of Pen. chrysogenum formed under the effect of this substance. NDMU induced a mutant of Pen. chrysogenum capable of selective synthesis of 6-aminopenicillinic acid without addition of the precursor.     

Genetic transformation of the mycelium fungi <Emphasis Type="Italic">Acremonium chrysogenum</Emphasis>

The system of transformation of heterologous genes under the method of agrobacterial transfer into Acremonium chrysogenum ATCC 11550 wild-type strains, natural producents of beta-lactam antibiotic cephalosporin C, and strains highly producing cephalosporin C no. 26/8 revealed by the multistage selection on its basis were developed. Vectors for agrobacterial transformation of A. chrysogenum containing expression cassettes of genes encoding resistance to geneticin (G418) and bleomicin (Zeocin^TM) antibiotics under control of Ashbya gossypii and Saccharomyces cerevisiae TEF1 promoters were constructed. A comparable assessment of agrotransformation methods while co-cultivating fungi and agrobacterial cells on filters and in deep culture was conducted. Transformants, selected by resistance to geneticin and bleomicin, were characterized by PCR and Southern blot analyses.     

Induced variability in Acremonium chrysogenum, a producer of neutral-alkaline proteases and peptidases

Lethal and mutagenic effects of N-nitrosomethyl biuret on the organism producing a complex of proteolytic enzymes i. e. Acremonium chrysogenum were studied. It was shown that methionine inhibited production of the protease complex in the induced prototrophic mutants. The selected mutants were classified according to the level of enzyme biosynthesis induction by methionine.     

Structure peculiarities of cell walls of <Emphasis Type="Italic">Acremonium chrysogenum</Emphasis>—an autotroph of cephalosporin C

Alterations of cell walls of Acremonium chrysogenum occurring at intensive synthesis of cephalosporin C has been studied. It is shown, using electron microscopy, that the cell wall of the cells of ATCC 11550 strain (“wild” type) became looser and thicker during growth. The cell wall of the cells of strain 26/8 (hyperautotroph of cephalosporin C) considerably degraded by the end of the stationary phase. Biochemical analysis has shown that these alterations entailed decrease of the proteins’ content covalently or noncovalently linked with the polysaccharides of cell walls of both strains. An increase of sensitivity of cell walls of the strain-hyperautotroph to an activity of lytic enzymes of chitinase, laminarinase, proteinase K, and lyticase preparation has been observed during the growth, but this increase has not been found in the case of “wild” type strain. The obtained results evidence to the structure failure of the cell wall of A. chrysogenum entailing the intensive creation of antibiotic.