[Effect of some cations on activity of macrotetralide synthase during development of Streptomyces chrysomallus subsp. Macrotetalidi]. / Vliianie nekotorykh kationov na aktivnost' makrotetralidsintazy v protsesse razvitiia Streptomyces chrysomallus subsp. Macrotetralidi.

The activity of a specific enzymatic complex, macrotetralide synthase, is observed at all stages of Streptomyces chrysomallus subsp. macrotetralidi development. Both synthase (esterase) and hydrolase activities of the enzyme may be realized in cell-free homogenate in cultures of different age under different conditions of culturing. Hydrolase activity is observed during Streptomyces growth in synthetic and natural media with high Ca levels starting from the moment of inoculation up to the end of the third hour, when the mycelium contains the maximal level of sodium. Esterase activity is realized in cultures aged 6 hours no matter what the culturing conditions are, with the maximum of this activity observed in 12-hour mycelium in the presence of the highest level of potassium. The presence of calcium in culture medium caused the appearance of hydrolase activity of macrotetralide synthase. The possibility of enzymatic and nonenzymatic hydrolysis of antibiotics in macrotetralide producer cells has been demonstrated.

[Directed search for streptomycetes that are producers of ionophoric antibiotics]. / Napravlennyi poisk streptomitsetov--produtsentov ionofornykh antibiotikov.

Streptomyces producing ionophore antibiotics were searched for in various natural substrata, such as soil, sea water, and coastline sea mud, in many geographical regions. A total of 393 Streptomyces strains were isolated, 308 of which proved to be capable of producing antibiotics; 135 of these contained water-insoluble antibiotically active substances in the mycelium. Studies by radioindication, spectrophotometry, and potentiometry demonstrated that these partially purified hydrophobic antibiotics possessed ionophore properties. Selectivity to monovalent potassium and ammonium cations seems to be a characteristic feature of hydrophobic antibiotics derived from Streptomyces differing them from other bacteria.

[Level of sodium and potassium in Streptomyces chrysomallus subsp. macrotetrolidi cells--producers of macrotetralide antibiotics]. / Soderzhanie natriia i kaliia v kletokakh Streptomyces shrysomallus subsp. macrotetrolidi--produtsenta makrotetralidnykh antibiotikov.

The ionophoretic macrotetrolide antibiotics selective to monovalent cations K+ and mainly to NH4+ were determined during the lag period of culture growth. At this stage the cells contain the maximal amounts of Na+ and K+. Macrotetrolides, whose selectivity to Na+ and K+ varies, can regulate the intracellular content of these cations by participating in the cation transport. The authors propose that the cells possess furosemide sensitivity and K+/Na+ ATPase transport systems.

[Calcium transport in cells of Streptomyces chrysomallus var. macrotetrolidi-- a producer of macrotetrolide antibiotics]. / Transport kal'tsiia v kletkakh Streptomyces chrysomallus var. macrotetrolidi--produtstenta makrotetrolidnykh antibiotikov.

The dynamics of calcium accumulation by cells in batch cultures and by washed cells was defined with a radiotracer procedure for Streptomyces chrysomallus var. macrotetrolidi producing ionophore macrotetrolide antibiotics. It was shown that macrotetrolides added to the cultivation medium could regulate intracellular contents of calcium by participating in cation transport. Moreover, possible functioning of a Ca-ATPase system for the calcium active transport in the streptomycete cells was demonstrated.

[The dependence of the distribution of ionophoric macrotetrolide antibiotics on the composition of their immiscible phases]. / Zavisimost' raspredeleniia ionofornykh antibiotikov makrotetrolidov ot sostava nesmeshivaiushchikhsia faz.

Influence of various solvents on the content of macrotetrolides during their prolonged storage in solution was shown. Under the conditions of room temperature 90 per cent acetone induced hydrolysis of polyether antibiotics. 90 per cent ethanol and dry chloroform induced respectively slight and intensive cyclization of linear precursors (oxyacids). The study on distribution of macrotetrolides between immiscible phases of various composition revealed that addition of ethanol or acetone to the water-chloroform system of organic solvents induced the antibiotic liberation into the water phase which increased with increasing concentration of the substances being added. Inorganic cations intensified the process during either the oxyacid cyclization or the antibiotic hydrolysis and liberated the reaction products from the equilibrium mixture. Under such conditions the value of the ion radius or selectivity of the macrotetrolides to definite cations was in principle of no importance.

[Coefficients of distribution of cyclic polyether macrotetrolide antibiotics between hydrophobic and hydrophilic solvents]. / Koéffitsienty raspredeleniia tsiklicheskikh poliéfirnykh antibiotikov makrotetrolidov mezhdu gidrofobnymi i gidrofil'nymi rastvoriteliami.

Dependence of distribution of 14C-macrotetrolide antibiotics between water and chloroform on the presence of various additives in the aqueous phase was studied with the radioindicator procedure. It was shown that in comparison to distilled water aqueous solutions of chlorine salts of ammonium, potassium and sodium increased the content of macrotetrolides in chloroform as a result of forming strong hydrophobic complexes. This is especially applied to the ions of ammonium whose addition to the aqueous phase led to an increase of macrotetrolide level in chloroform up to 98.4 per cent. Addition of weak hydrochloric acid or alkaline agents resulted in marked transfer of the ionophores into the aqueous phase at the expense of hydrolysis of the antibiotic cyclic molecules. The highest hydrolysis levels were induced by potassium hydroxide, the content of the ionophores in the hydrophobic phase decreasing up to 90.6 per cent. The effect of picric acid on distribution of the macrotetrolides between water and chloroform was different and depended on its concentration.