[Phagoresistance of filamentous cyanobacteria clones]. / Priroda fagorezistentnosti klonov nitchatykh tsianobacterii.

The paper deals with formation regularities of phagoresistant clones of cyanobacteria in two productive virus-cell systems: heterocyst cyanobacterium Nostoc linckia--cyanophage N-2, and mutant in heterocysts strain of Anabaena variabilis--cyanophage A-1. Frequency of spontaneous formation of phagoresistant clones of cyanobacterium N. linckia varies within 1.0-8.0 x 10(-6) per a cell, A. variabilis--5.0 x 10(-6)-7.0 x 10(-7) per cell. All the studied phagoresistant clones of N. linckia have identical morpho-cultural properties and do not differ from those of the initial culture. Phagoresistant clones of A. variabilis are presented by two groups. One of them, as to its properties, does not practically differ from the wild type culture. The second group differs considerably from the initial culture A. variabilis as to a number of characteristics--time of colonies appearance, their amount, length of trichomas, specific rate of growth and biomass accumulation. Spontaneous transfer of cyanophages to the culture liquid of clones resistant forms of cyanobacteria has not been revealed. Lysis of cells of the studied clones also was not induced under the effect of mytomycin C, thermal treatment and UV-irradiation. Cyanophage N-2 is not adsorbed by the cells of resistant cloned forms of cyanobacteria N. linckia. Only nonspecific adsorption takes place on the cells of phage-resistant clones of A. variabilis of both groups: about 20% of virions introduced in the adsorption mixture. Basing on the data obtained, it is supposed that phage-resistance of stable clones of filamentous cyanobacteria under the conditions of the given experiment is determined by the structure modification of cells receptors.

[Activity of tricarboxylic acid cycle enzymes in cyanobacteria Spirulina platensis]. / Izuchenie aktivnosti fermentov tsikla trikarbonovykh kislot tsianobacterii Spirulina platensis.

The activity level and some physico-chemical properties of enzymes of the tricarboxylic acid cycle (TCA cycle) and the associated enzymes isocitrate lyase and glutamate dehydrogenase of cyanobacterium Spirulina platensis grown under illumination of 5000 lk in batch conditions, have been studied. High activities of most of the studied enzymes except for alpha-ketoglutarate dehydrogenase (alpha-KGDH) and succinate dehydrogenase have been estimated. In some cases the activities were by an order higher than that of similar enzymes in other cyanobacteria. This reflects the microorganism ability to synthesize intensively organic substances and first of all protein. Absence of alpha-KGDH activity proves that TCA cycle of spirulina has a limited value for energy generation and mainly performs the biosynthetic function.

[Effect of reproduction of the LPP-3 cyanophage on glutamate dehydrogenase and glutamine synthetase activity in the cyanobacterium Plectonema boryanum]. / Vliianie reproduktsii tsianofaga LPP-3 na aktivnost glutamatdegidrogenazy i glutaminsintetazy v kletakh tsianobakterii Plectonema boryanum.

The effect of cyanophage LPP-3 reproduction on glutamate dehydrogenase and glutamine synthetase (GS) in P boryanum cells have been studied. It was determined that the both reactions are intensified by 135% and 220%, accordingly. Isoenzymes of GS were purified from native and infected cell of cyanobacteria. Their physical-and-chemical properties are different. The cyanophage development probably causes specific modification of the cell enzymes.

[Aspartate kinase activity of Cyanobacteria Anabaena variabilis]. / Aspartatkinaznaia aktivnost' tsianobakterii Anabaena variabilis.

Aspartate-kinase (ASK) activity of filamentous cyanobacteria A. variabilis and its dependence on physico-chemical factors and substrate concentration in the reaction mixture have been studied. Three isoenzymes ASK-1, ASK-2 and ASK-3 which differ in the values of pH-optima, molecular weight, isoelectric points and effector of retro-inhibition have been isolated by ion-exchange chromatography. High level of inhibition of summary ASK of the cell-free extract can be reached only in a case of simultaneous addition of all amino acids, the final products of this biosynthetic pathway into the incubation mixture.

[Isolation, purification and various properties of aspartate kinase from the cyanobacterium Plectonema boryanum]. / Vydelenie, ochistka i nekotorye svoistva aspartatkinazy tsianobakterii Plectonema boryanum.

The enzymic activity of aspartate kinase from filamentous cyanobacteria Plectonema boryanum at the logarithmic phase of growth has been studied. Aspartate kinase was purified eleven times and extracted in functionally homogeneous state from the cell-free extract by the methods of ammonium sulphate salting-out, ion-exchange chromatography and isoelectric focusing. Some physical and chemical characteristics of the enzyme have been studied: pI-7.2; optimum pH-9.0; optimum temperature-55 degrees C. The dependence of enzymatic reaction on concentration of substrates, co-enzymes, cofactors and protein has been established. Regulation of aspartate kinase activity by amino acids of the aspartate family has been investigated. L-threonine, L-homoserine and L-isoleucine (0.01-0.001 M) have a pronounced inhibitory effect. L-lysine and L-methionine are not immediate inhibitors of aspartate kinase but intensify the inhibitory effect of threonine by the cumulative mechanism.