适应性进化提高淀粉酶产色链霉菌T17自发酸胁迫抗性的生理机制

Physiological Mechanism by Which Adaptive Evolution Improves the Resistance of Streptomyces diastatochromogenes T17 to Spontaneous Acid Stress

考察ε-聚赖氨酸产生菌淀粉酶产色链霉菌(Streptomyces diastatochromogenes)T17,及其经酸性适应性进化得到的3株进化菌株(S.diastatochromogenes AE41、S.diastatochromogenes AE51和S.diastatochromogenes AE56)应对自发酸胁迫的生理响应。比较2个胁迫时间下原始菌株和进化菌株相关生理指标的变化。结果显示,在第0小时(pH 6.5),原始菌株和进化菌株的各生理指标无明显区别;在第48小时(pH 3.2),相较于原始菌株,进化菌株的耐酸能力更强,胞内pH值、ATP含量和H+-ATPase活性均明显提高,胞内天冬氨酸、丙氨酸、谷氨酸、赖氨酸、甘氨酸以及脯氨酸浓度明显增加,细胞膜脂肪酸的不饱和度明显增加从而提高流动性。进化菌株能够实现对自发酸胁迫的制衡。

The physiological responses of theε-poly-L-lysine-producing strain Streptomyces diastatochromogenes T17 and its acid-resistant derivatives,S.diastatochromogenes AE44,S.diastatochromogenes AE51 and S.diastatochromogenes AE56,to spontaneous acid stress were investigated.The changes in relevant physiological indexes of the original and evolutionary strains were compared at two stages of acidic stress.The results showed that at 0 h(pH 6.5),there were no significant differences in the physiological indexes between the original and evolutionary strains.At 48 h(pH 3.2),compared to the original strain,the intracellular pH,ATP concentration and H+-ATPase activity of the evolutionary strains were significantly increased,accompanied by increased levels of intracellular aspartic acid,alanine,glutamic acid,lysine,glycine and proline.The ratio of unsaturated to saturated fatty acids(U/S ratio)in the cell membrane was also increased so that the membrane fluidity was improved.Collectively,we conclude that the evolutionary strains could achieve a balance during spontaneous acid stress.