Study On Physiology And Biochemistry Characters Of Antarctic Ice Microalgae Chlamydomonas Sp. L4 Chloroplasts And Its Acclimation To Low Temperature

The South Pole is one of the coldest areas on the earth. Cold is characteristic that distinguishes this area from other areas. The sea ice is important constituent for the polar physics environment. Antarctic ice microalgae refers to micro algae which lives in the Antarctic sea ice, the sea ice edge or water. It is within this labyrinth that the sea ice microalgae live with the only liquid being pockets of concentrated brines. At the same time, it is a low sunlight, poor nutrition and less air exchanges in the ice sheet. When sea ice melts in every spring and summer, the environments around the ice microalgae change enormously acclimating the frequent freeze-thaw cycles, Antarctic ice microalgae form gradually a series of physiological and biochemical mechanisms to adapt these extreme changeable environments.Just because of special physiological characteristic, ice microalgae have been used as fine tested materials to cryobiology and potential source of the new-style active substances. For reasonable development of Antarctic ice microalgae, increase of existing microbial resources, discovery of valuable active substances and products, and the new materials for fundamental researches, further study on the adversities acclimation of thylakoid membranes compositon of Antarctic ice microalgae Chlamydmonas sp. L4 is carried out.1 By optical microscope, scan and transmission microscopes, the morphology and ultrastructure of Antarctic ice microalgae Chlamydomonas sp. L4 cultured in normal environment and chilling environment were studied. Comparing with normal temperature green microalgae, the main characteristics of Antarctic ice microalgae Chlamydomonas sp. L4 were as followed: relatively thick cell wall, obvious plasmolysis phenomena at the end; much black particles between cell wall and membrane. In addition, much lipid and starch particles, as the important storage components, played an important role in the survival of Antarctic ice microalgae Chlamydomonas sp. L4 in Antarctic area. The chloroplast of Antarctic ice microalgae Chlamydomonas sp. L4 was irregular and spread all over the cell, and all of these were the adaptation to extreme environment. After chilling stress, the mitochondria was basically steady, which maintained the fundamental metabolism of organisms.But the thylakoid became blurry, contorted and bulgy.The chloroplasts were isolated by centrifugation through sucrose gradient. The grade of purity and the yield of the chloroplasts were appropriate.2 Regarding Antarctic ice microalgae Chlamydomonas sp. L4 normal cultured as control, we compared the changes of pigment, lipoid, fatty acid and pigment protein complexes in thylakoid membranes,and analyzed the functions of each composition: (1) LHC plays an important role in the adversities acclimation of icing ,as it contains abundant chlorophyll b; xanthophylls can asist in the dissipation of photosynthesis under chilling stress, and improve the the mobility of Antarctic ice microalgae Chlamydomonas sp. L4 thylakoid membranes. (2) MGDG can maintain the especial configuration of thylakoid membranes; 18:3ω9 can not only improve the the mobility of the Chlamydomonas sp. L4 thylakoid membranes, but also can accelerate the functiong of D1 protein. 16:1ω3t can reduce the content of the'high melting point'fatty acid. (3) The content of PSⅠ, H+-ATPase, Cytb6f and RUBPase maintained under chilling stress, possibly it accerlerated the photophosphorylation. LHCⅡis a pivotal component in the adversities acclimation.3 By studying the influence of chilling to the mobility, harm and function of Antarctic ice microalgae Chlamydomonas sp. L4 thylakoid membranes, we got many results: The liquidity of its thylakoid membranes is maintained by adjusting component under chilling stress. As a whole , chilling causes little harm to Chlamydomonas sp. L4 thylakoid membranes, SODase plays an important role in protecting the thylakoid membranes. By analyzing the Hill-reaction activity of Chlamydomonas sp. L4 thylakoid membranes during chilling stress, we found the speed of photosynthesis became lower early and came back later. As a result of the high activity of H+-ATPase in Chlamydomonas sp. L4 thylakoid membranes during chilling stress, the photosynthesis reaction runs natural.We explored a series of physiological and biochemical mechanisms by analystting the the morphology and ultrastructure of Antarctic ice microalgae Chlamydomonas sp. L4, the biochemistry composition of Antarctic ice microalgae Chlamydomonas sp. L4 thylakoid membranes and physiological function of Antarctic ice microalgae Chlamydomonas sp. L4 thylakoid membranes.