Зміни деяких фізіолого-біохімічних показників у представників Chlorophyta та Cyanoprokaryota за різних температур

Abstract

Досліджено зміни сухої маси, концентрації хлорофілу а, активності сукцинатдегідрогенази (CДГ) та цитохромоксидази у деяких видів Chlorophyta (Desmodesmus communis, Tetraedron caudatum) та Cyanoprokaryota (Aphanocapsa planctonica, Phormidium autumnale f. uncinata) за різних температурних режимів – 20, 26, 32 °С. Максимальна величина сухої маси D. communis і T. caudatum відзначалася за температури 20 °С, а Aph. planctonica – 32 °С. За температурних умов, які виходять за межі оптимальних для росту досліджуваних видів водоростей та ціанопрокаріот, вміст хлорофілу а у їх сухій масі знижувався. У зелених водоростей за досліджуваних температур суттєвих змін у функціонуванні СДГ не відбувалося. Натомість, у ціанопрокаріот з виходом культур на стаціонарну фазу росту за найвищої температури спостерігалося повне інгібування активності СДГ. Зміни показників активності цитохромоксидази за досліджуваних температурних режимів у представників Chlorophyta та Cyanoprokaryota мали подібний характер і залежали не лише від температури, але і фази росту культур.

Исследованы изменения сухой массы, концентрации хлорофилла а, активности сукцинатдегидрогеназы (СДГ) и цитохромоксидазы в некоторых видов Chlorophyta (Desmodesmus communis, Tetraedron caudatum) и Cyanoprokaryota (Aphanocapsa planctonica, Phormidium autumnale f. uncinata) при разных температурных режимах - 20, 26, 32 °С. Максимальная величина сухой массы D. communis и T. caudatum отмечалась при температуре 20 °С, а Aph. planctonica - 32 °С. При температурных условиях, которые выходят за пределы оптимальных для роста исследуемых видов водорослей и цианопрокариот, содержание хлорофилла а в их сухой массе снижалось. В зеленых водорослей при исследуемых температурных условий выращивания существенных изменений в функционировании СДГ не происходило. Зато в цианопрокариот с выходом культур на стационарную фазу роста при высокой температуре наблюдалось полное ингибирование активности СДГ. Изменения показателей активности цитохромоксидазы по исследуемых температурных режимов у представителей Chlorophyta и Cyanoprokaryota имели сходный характер и зависели не только от температуры, но и фазы роста культур.

Different temperature regime (20, 26, 32 °С) effect on the changes of dry weight, chlorophyll a content and key enzymes of respiratory metabolism activity (succinate dehydrogenase and cytochrome oxidase) in some species of Chlorophyta (Desmodesmus communis, Tetraedron caudatum) and Cyanoprokaryota (Aphanocapsa planctonica, Phormidium autumnale f. uncinata) was investigated. With the cultivation temperature of green microalgae Desmodesmus communis and Tetraedron caudatum increasing from 20 °C to 26 °C and 32 °C, the decrease of dry mass is observed that indicates the inhibition of their growth processes. At the same time the increase of dry weight at temperatures of 26 °C and 32 °C as compared with 20 °C in representatives of Cyanoprokaryota Aphanocapsa planctonica was noted. This fact indicates that this species of Cyanoprokaryota is more adapted to existence at higher temperatures than the studied species of Chlorophyta. In response to the cultivation temperature changing from 20 °C to 26 °C and 32 C the chlorophyll a concentration in dry weight of green algae Desmodesmus communis and Tetraedron caudatum decreased, and of Cyanoprokaryota representatives - Aphanocapsa planctonica and Phormidium autumnale f. uncinata, conversely, increased. Thus, at temperature conditions that are outside of the optimal for algae growth of species Chlorophyta and Cyanoprokaryota investigated the chlorophyll a content in their dry mass decreased. It is important to consider this fact when evaluating phytoplankton biomass by chlorophyll a indices in the hydrobiological research practice. Chlorophyll a content decrease observed in green algae under the influence of elevated temperature may indicate, on the one hand, the inhibition of pigment biosynthesis, and, on the other hand, the acceleration of its destruction. It has been established that the activity of respiratory metabolism enzymes (succinate dehydrogenase and cytochrome oxidase) depends on the temperature regime of cultivation, the age and culture species. In both green algae at the studied temperatures (20 °C, 26 °C and 32 °C) there were no considerable differences in the succinate dehydrogenase activity that indicates the absence of significant changes in tricarboxylic acid cycle functioning. The dynamics of cytochrome oxidase activity indices under the influence of culture medium temperature of 26 C and 32 C as compared with 20 C in Desmodesmus communis and Tetraedron caudatum had a phase character: if the reactivity of the enzyme is rapidly increased in the exponential growth phase (the 14th day), then with the culture reaching the stationary phase of growth (the 28th day) it remained almost unchanged (at 26 °C) or was completely inhibited (at 32 °C). Significant inhibition of the cytochrome oxidase activity under the influence of maximal temperature indicates a violation of the mitochondrial respiratory chain functioning in representatives of Chlorophyta. The saving of the succinate dehydrogenase high activity in these conditions is probably caused by the alternative pathway of electron transport activation, related with the functioning of alternative oxidase. The indices of succinate dehydrogenase and cytochrome oxidase activity in representatives of Cyanoprokaryota Aphanocapsa planctonica and Phormidium autumnale f. uncinata were smaller at minimal temperature (20 °C) than at the temperature of 26 C. This is consistent with the results of our research concerning the lowest dry weight and chlorophyll a content in representatives of Cyanoprokaryota at the specified temperature regime of culture medium and it indicates a slowdown of their metabolism. In conditions of the maximal temperature effect (32 °C) compared with the other investigated on the exponential growth phase of cultures Aphanocapsa planctonica and Phormidium autumnale f. uncinata the reactivity of the both enzymes significantly increased while with culture reaching the stationary phase of growth the reactivity, in contrast, decreased. Cytochrome oxidase and succinate dehydrogenase activities significant decrease with Cyanoprokaryota cultures aging at 32 °C indicates the inhibition of aerobic respiration in them. Obviously the processes of energy supply in Aphanocapsa planctonica and Phormidium autumnale f. uncinata occur anaerobically under these conditions.