| Antarctica region, due to its specific geographical position and climate, which characterized by strong seasonal changes in light and UV intensity, is considered to be an extreme environment. Antarctic sea environment, which is under low temperature (usually-1.8℃~2.0℃) for all time and high salinity (34‰~35‰in sea water, 150‰in sea ice saline channels). To be colonized in this low-temperature, strong radiation and high-salinity environment, microorganisms form gradually a series of physio- logical, chemical and molecular mechanisms. Therefore, Antarctic microorganisms provide a useful model system for studying cold adaptation, and also are the optimal sources of low temperature bioactive substances ( cold-adapted enzymes , PUFA) and cold-adapted biological engineering bacteria. With the development of sea oil field exploitation and ocean transportation more frenquently, oil hydrocarbon pollution in the sea occurs more seriously. Antarctica, which thought to be the last unpolluted land, were polluted by petroleum oil. Recently, with the development of Antarctic Exploration, mine exploitation and travelling, especially gigantic oil tanker sinking, plenty of pertoleum hydrocarbon leaked out and the security of Antarctic ecosystem had been threatened. The phenomenation had attracted attention of every country. It is so fragile as Antarctic ecosystem that any little pollution could result in serious breakage to ecosystem Bioremidiation is an important method in eliminating oil pollutants from sea, this thesis aims at purpose of which cold-adapted hydrocarbon- degrading bacteria are screened and that will play an fundermental role used for bioremediation technique and method of eliminating sea oil pollution at low tempera- ture.The method of combination MMC liquid culture with MMC agar plate culture was used for screening petroleum hydrocarbon-degrading cold-adapted bacteria from Antarctic seawaters and sea-ice. Tests of bacteria growing and degradation efficiency were carried. Molecular identification of 16S rRNA amplified from four Antarctic cold-adapted degrading bacteria and phylogenetic tree based on 16S rRNA gene was carried. Antarctic cold-adapted degrading bacteria NJ49 was chosen to study the optimization of nutrition and growing condition.Tests of naphthaline degradation, degradable diesel chromatogram, dehydrogenase production, biosurfactant produc- tion, fatty acid change were carried for Antarctic cold-adapted degrading bacteria NJ49 degradation characteristic and cold adaptation study. The results were sum- marized as follows.1. Four petroleum hydrocarbon-degrading cold-adapted bacteria (namely NJ41, NJ44, NJ49, NJ289 ) were screened from Antarctic sea waters and sea-ice samples. Viable counts results showed that four Antarctic cold-adapted degrading bacteria grew well and Antarctic cold-adapted degrading bacteria NJ49 cell number was near to 106.8CFU/ml after twenty days. Degradation datas showed that degradable ablilities of four Antarctic cold-adapted degrading bacteria were different separatetly and degradation efficiency of Antarctic cold-adapted degrading bacteria NJ49, value 68%, were the highest.2. Morphological characteristics results showed that Antarctic hydrocarbon- degrading bacteria NJ41 was spherical,diameter 1.0~1.2μm, and other three bacteria were bacilliform, long 0.7~2.8μm. All Antarctic cold-adapted degrading bacteria did not form spore and all of them had flagellum to move. Results of 16S rRNA identification revealed that Antarctic cold-adapted degrading bacteria NJ41, NJ49 and NJ289 belonged to the described genus Planococcus, Shewanella, Pseudo- alteromonas, respectively. Antarctic cold-adapted degrading bacteria NJ44 need to be studied further.3. Antarctic cold-adapted degrading bacteria NJ49 was chosen to study the optimization of nutrition and growing condition. Results revealed that the optimal combination of nutrient constituents and condition to grow and degrade were determined as NH4NO3, KH2PO4 and K2HPO4, NaCl 6%, pH 7.5, 15℃, 80ml volume. Adding biosurfactant, especially combination negative ion surfactant (SDS) with positive ion surfactant (rhamnolipid) could improve Antarctic cold-adapted degrading bacteria NJ49 growing and degrading.4. Degradation characteristics results showed that Antarctic hydrocarbon- degrading bacteria NJ49 may grow in MMC culture, naphthaline as the sole carbon and energy source and degrade naphthaline at 15℃. Degradable diesel chromatogram revealed that there were eighteen alkane ingredients (C9~C26 ) in control diesel, while only seven alkane ingredients (C15~C21 ) in Antarctic cold-adapted degrading bacteria NJ49 degradable diesel. Furthermore, every alkane ingredients content was decreased. The results of dehydrogenase production revealed that dehydrogenase activity of Antarctic cold-adapted degrading bacteria NJ49 was much lower at 5℃than at 20℃. That indicated low temperature limited enzyme activity. Dehydrogenase activity was higher in 2216E amended diesel than in 2216E culture, indicating that the dehydrogenase may be diesel-degrading enzyme. Results of biosurfactant production showed that Antarctic cold-adapted degrading bacteria NJ49 did not produce bio- surfactant at both 5℃and 20℃. Data of fatty acid change revealed that ouccrred change at low temperature(5℃)condition. Fatty acid components and single fatty acid number were increased induced by low temperature(5℃). Antarctic hydrocarbon- degrading bacteria NJ49 isolate produced kinds of unsaturated fatty acids and the content of them were much higher at 5℃than mesothermal condition(20℃). Saturated degree of Antarctic cold-adapted degrading bacteria NJ49 fatty acid decreased from 1.22 to 0.77 at low temperature(5℃), which indicated that the Antarctic cold-adapted degrading bacteria NJ49 adapt cold condition to degrade by changing fatty acid.Marine bacteria capable of degrading petroleum hydrocarbon at low temperature were isolated from Antarctic seawaters and sea-ice samples, which was the first time in civil country. The Antarctic cold-adapted degrading bacteria provided bacteria sources used for bioremediation of sea oil pollution in our country. The study of degradation characteristics of Antarctic cold-adapted degrading bacteria at low temperature provided efficient bioremediation technique and method of eliminating sea oil pollution at low temperature.
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