相似相容物质对嗜冷甲烷叶菌R15的冷保护作用

Cryoprotection of compatible-solutes for Methanolobus psychrophilus R15

嗜冷甲烷叶菌R15(Methanolobus psychrophilus R15)是本实验室分离自青藏高原若尔盖湿地的一株甲烷古菌新种。前期研究发现其生长温度范围为0℃-30℃,最适生长温度为18℃,并能在5 mmol/L至800 mmol/L NaCl中生长。【目的】鉴定甲烷古菌的相似相容物质,并探讨它们对甲烷古菌的冷保护作用和可能的作用机理。【方法】用LC-MS分析低温下甲烷古菌胞内积累的相似相容物质;检测积累的及已知的相似相容物质对R15低温生长的促进作用,并以研究酶稳定性的模式蛋白谷氨酸脱氢酶(GDH)为对象,分析相似相容物质对低温下酶的稳定性作用。【结果】在4℃培养和冷胁迫的R15细胞内检测到胆碱和甜菜碱的积累;发现胆碱、甜菜碱、甘氨酸、肉毒碱、乙偶姻和四氢嘧啶6种相似相容物质促进R15的低温生长,而且胆碱、甜菜碱及甘氨酸能提高GDH酶的低温稳定性。【结论】甲烷古菌的相似相容物质同时具有低温保护作用,本研究扩展了对相似相容物质生理功能的认识。

Methanolobus psychrophilus R15, isolated from the Zogei wetland at Tibetan plateau, is a cold-active methanogenic archaeon growing from 0 to 30℃ and optimally at 18℃. R15 grew in the NaC1 concentrations ranging from 5 to 800 mmol/L. [ Objective] This study aimed to find compatible solutes that can improve the growth of R15 at cold, and the possible function as cryoprotectant. [ Methods] Using LC-MC we determined the accumulated substances in the R15 cells growing at lower temperatures, as well as in the cold-shocked cells; by supplementing the accumulated substances and the chemicals known as the bacterial compatible solutes in the R15 culture, we detected their functions of assisting the cold-growth of R15 ; by adding the detected compatible solutes into the glutamate dehydrogenase （GDH） , we determined the enzymatic stabilities at lower temperatures. [ Results] Choline and betaine were accumulated both in the 4℃-cultured and 42：-shocked 302： culture of R15. It was determined that choline, betaine, glycine, carnitine, acetoin and ectoine all improved the growth of R15 at cold. Choline, betaine and glycine could enhance the stability of GDH at low temperature. [ Conclusion] Some compatible solutes can act as the cryoprotectant for methanogenic archaea, which expands our knowledge of the physiological functions of the compatible solutes.