IHB OpenIR  > 学位论文
Thesis Advisor刘永定
Degree Grantor中国科学院水生生物研究所
Place of Conferral中国科学院水生生物研究所
Degree Discipline水生生物学
Keyword变重力 模拟微重力 细胞生物学 水生生命封闭生态系统 微藻微重力胁迫
Other AbstractExperimental data on the rearrangements of organelle structural and functional organization and cell adaptation strategy in plant organisms, the role of the second messengers in mechanisms of graviperception as well as the controlled ecological life support system (CELSS) under altered gravity are reviewed. In the present report, studies on biological effects of algae under altered gravity were performed. The focus was on the changes in metabolism of cytoplasmic membrane, adaptive responses of antioxidative systems and development of heterocyst in algal cells under microgravity. At the same time, a hydrobiological closed ecosystem (Chorelh pyrenoids + Bulinus australianus) was chosen to conduct a study on their structure and function in hypergravity environment. Responses of microalgae to hypergravity provided by centrifuge in multipurpose space biological incubator were studied. Under hypergravity condition (1.4g), some physiological characteristics of microalgae indicated increased responses. Anabaena cells in hypergravity showed increases of photosynthetic O2 evolution and respiration, especially, marked increase was observed in respiration. The 77K fluorescence emission spectra indicated that the activity of PS II was higher in hypergravity-treated Anabaena cells than in lg control. The above results suggest that hypergravity is an energy-consumed environmental stress to Anabaena cells. To provide direct evidences for effects of microgravity on structure and function of plasma membrane, malondialdehyde (MDA) content was examined on the basis of quantitative reaction of both MDA and thiobarbituric acid (TBA), and electrolyte leaking was determined with conductometer model DDS-11A. Experiments showed that Lipid peroxidation became stronger and the content of MDA increased, Meanwhile, the membrane permeability increased in cells of both Anabaena sp PCC7120 and Synechococcus 7942 under simulated microgravity. Our results suggested that there is some commonness between microgravity stress and other environmental stresses, and cytoplasmic membrane is a possible primary site of microgravity effects in most cell types not specialized for perception of gravity, such as alga cells. The membrane permeability and photosynthetic characteristics of Anabaena cells under microgravity in different concentrations of Ca2+ were measured. Our results showed that increased Ca2+in medium could alleviate membrane permeability induced by microgravity, and lessened the decreasing range of photochemistry efficiency (expressed as Fv / Fm) in Anabaena cells. Exogenous Ca2+ might enhance structural and functional stabilization of plasma membrane. Moreover, exogenous Ca2+ might alleviate the microgravity-induced damage of photosynthesis of Anabaena cells under microgravity environment. The treatment with Ca2+ channel inhibitor showed that the second messenger was involved in the protective process. It was found that reactive oxygen species (ROS) in Anabaena cells increased under simulated microgravity provided by clinostat. Activities of intracellular antioxidant enzymes, such as Superoxide dismutase (SOD), Catalase (CAT) were higher than those in the controlled samples during the 7 days' experiment. However, the contents of Gluathione (GSH), an intracellular antioxidant, decreased in comparison with the controlled samples. The results suggested that microgravity provided by clinostat might break the oxidative / antioxidative balance. It indicated a protective mechanism in algal cells, that the total antioxidant system activity increased, which might play an important role for algal cells to adapt the environmental stress of microgravity. Effect of simulated microgravity on differentiation of heterocyst was studied in Anabaena sp. PCC 7120. Our data showed that wild type strains(control) reduced the content of chlorophyll, the ratio of Fv/Fm related to activity of PS II, and degraded its phycocyanin during nitrogen starvation, further, formed heterocyst. In contrast, the clinostat-treated strains increased chlorophyll a content and couldn't degrade its phycocyanin. No heterocyst was observed. These results suggested that microgravity inhibits differentiation of heterocyst, at least mAnabaena sp. PCC 7120. One closed aquatic microsystem containing Chlorella, Bulinus australianus was chosen to conduct a study on their structure and function in space. The closed microsystem was run in hypergravity environment for the first time. The species composition was maintained for 7 days. The results obtained from the microsystem showed that there was a self-regulation in coupling production and consumption, which made the artificial microsystem very stable in hypergravity during experimental time. The closed aquatic "producer-consumer" system is an ideal experimental and theoretical model for study of CELSS applied in space.
Document Type学位论文
Recommended Citation
GB/T 7714
李根保. 变重力对微藻的生物学效应研究[D]. 中国科学院水生生物研究所. 中国科学院水生生物研究所,2002.
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