Study on changes of plasmalemma permeability and some primary inorganic ions of Antarctic ice microalgae (Chlamydomonas sp. ICE-L) in the low-temperature stress

The changes of plasmalemma permeability and some primary inorganic ions of Antarctic ice microalgae （ Chlamydomonas sp. ICE-L） in the low-temperature stress were examined. The plasmalemma of 1CE-L could maintain the stability at the freezing condition of -6 ℃. That signifies that it could maintain the proper function of plasmalemma and stability of the intracellular environment during sea ice formation. The function of inorganic ions on low-temperature adaptation of ICE-L was investigated by using the X-ray microanalysis method. Low temperature （0 - -6 ℃ ） induces Ca^2 ＋ concentration increment of cytoplasm, but after 24 h the content decrease quickly to normal value. As a matter of fact, Ca^2 ＋ plays an important role as the second messenger in the low temperature adaptation of ICE-L. In addition, low temperature also influences on the other primary inorganic ions transfer and the cell maintains activity by keeping ratio balance among different ions. Above all, it is necessary for Antarctic ice microalgae to survive and breed by maintaining the stability of K^ ＋ content and the balance of Na^ ＋/Cl^ -.

Effect of Cd on GSH and GSH-related enzymes of Chlamydomonas sp.ICE-L existing in Antarctic ice

Glutathione(GSH) and GSH-related enzymes play a great role in protecting organisms from oxidative damage. The GSH level and GSH-related enzymes activities were investigated as well as the growth yield and malonyldialdehyde(MDA) content in the Antarctic ice microalga Chlamydomonas sp. ICE-L exposure to the different cadmium concentration in this paper. The results showed that the higher concentration Cd inhibited the growth of ICE-L significantly and Cd would induce formation of MDA. At the same time, it is clear that GSH level, glutathione peroxidases(GPx) activity and glutathione S\|transferases(GST), activity were higher in ICE-L exposed to Cd than the control. But GR activity dropped notably when ICE-L were cultured in the medium containing Cd. Increase of GSH level, GPx and GST activities acclimate to oxidative stress induced by Cd and protect Antarctic ice microalga Chlamydomonas sp. ICE-L from toxicity caused by Cd exposure. These parameters may be used to assess the biological impact of Cd in the Antarctic pole region environment.

Acclimatory responses to high-salt stress in Chlamydomonas (Chlorophyta, Chlorophyceae) from Antarctica

Antarctic ice microalga can survive and thrive in channels or pores containing high salinity in Antarctic ice layer. In this study, it was found that cell membrane permeability of green microalga Chlaraydomonas sp. L4 from Antarctic sea ice was high in cells treated with hypersalinity due to the induction of active oxygen and radicals. However, increased super oxide dismutase （SOD） scavenged harmful free radicals effectively to keep cell membrane integrity. Also, the analysis of membrane fatty acids demonstrated the content of saturated fatty acids and monounsaturated fatty acids in- creased and polyunsaturated fatty acids decreased under the high-salt treatment for 14 d, which effectively reduced the membrane fluidity and minimized the injury to cell membrane. The morpho- logical changes showed that hypersalinity induced the increase of cell volume and the consumption of starch granules. However, because of the increase in detoxification of vacuoles, electron-dense deposits and SOD activity under high-salt stress, the complete noninterference thylakoids, mito- chondria and cell nucleus maintained cellular fundamental metabolism. Global-expression profiling of proteins showed eight protein spots disappeared, 18 protein spots decreased and 18 protein spots were enhanced after the high-salt shock obviously （P 〈0.05）. One new peptide （pI 6.90; MW 51 kDa） was primarily confirmed as the processor of light reaction center protein CP43 in photosystem II, which increased photosynthesis ability of Chlamydomonas sp. L4 treated with high salinity.

Proteomic Alterations of Antarctic Ice Microalga Chlamydomonas sp.Under Low-Temperature Stress

Antarctic ice microalga can survive and thrive in cold channels or pores in the Antarctic ice layer. In order to understand the adaptive mechanisms to low temperature, in the present study we compared two-dimensional polyacrylamide gel electrophoresis （2-DE） profiles of normal and low temperature-stressed Antarctic ice microalga Chlamydomonas sp. cells. In addition, new protein spots induced by low temperature were identified with peptide mass fingerprinting based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry （MALDI-TOF-MS） and database searching. Well-resolved and reproducible 2-DE patterns of both normal and low temperature-stressed cells were acquired. A total of 626 spots was detected in control cells and 652 spots were detected in the corresponding low temperature-stressed cells. A total of 598 spots was matched between normal and stressed cells. Two newly synthesized proteins （a and b） in low temperature-stressed cells were characterized. Protein spot A （53 kDa, pl 6.0） was similar to isopropylmalate/homocitrate/citramalate synthases, which act in the transport and metabolism of amino acids. Protein spot b （25 kDa, pl 8.0） was related to glutathione S-transferase, which functions as a scavenger of active oxygen, free radicals, and noxious metabolites. The present study is valuable for the application of ice microalgae, establishing an ice microalga Chlamydomonas sp. proteome database, and screening molecular biomarkers for further studies.