Thermal Regulation of Aerobic and Anaerobic Synthesis of Unsaturated Fatty Acid.

从嗜冷细菌PseudoNonas sp.菌株E-3中分离到不饱和脂肪酸营养缺陷突变体，该突变体具有两种不同的不饱和脂肪酸代谢机制。为了对突变体进行表征，进行了生理生化研究。(1)突变体的生长速度和菌量与添加不饱和脂肪酸的浓度有关。当培养基中添加0.01%的油酸时，突变体的生长速度与亲本菌株几乎相同。(2)油酸是突变菌株在含油酸培养基上生长的磷脂中主要的不饱和脂肪酸成分。另一方面，在相同条件下生长的亲本菌株中，顺式异丙酸是主要的不饱和脂肪酸，而不是油酸。结果表明，亲本菌株磷脂的脂肪酸组成与外源添加的不饱和脂肪酸无关。(3)比较突变菌株和亲本菌株制备的脂肪酸在体外厌氧合成不饱和脂肪酸的反应。从放射性标记前体合成的不饱和脂肪酸的数量在两种菌株中几乎相同。(4)突变菌株的脂肪酸去饱和酶（脂肪酸去饱和酶是好氧机制的关键酶）活性低于亲本菌株的一半。此外，当细胞在由蛋白胨和饱和脂肪酸组成的培养基中培养时，突变菌株的酶活性不能被诱导。(5)突变菌株对厌氧途径抑制剂3-癸酰半胱胺的敏感性明显高于亲本菌株。上述结果表明，E-3假单胞菌的生长需要好氧和厌氧两种途径。

Unsaturated fatty acid auxotorophic mutant was isolated from a psychrotrophic bacterium, PseudoNonas sp. strain E-3, which possess two different mechanisms for unsaturated fatty acid. In order to characterize the mutant, physiological and biochemical studies were carried out.(1)Growth rate and bacterial mass of the mutant was dependent on the concentration of added unsaturated fatty acid(e. g. palmitoleic or oleic acid)in medium, and the mutant showed almost the same growth rate to that of the parent strain when 0.01% oleic acid was added in the medium.(2)Oleic acid was found to be a major unsaturated fatty acid component in the phospholipid from the mutant strain grown on the medium containing oleic acid. On the other hand, cis-vaccenic acid but not oleic-acid was a major unsaturated fatty acid in the parent strain grown under the same condition. It was found that the fatty acid composition of the phospholipid from the parent strain was independent on exogenously added unsaturated fatty acid.(3)Anaerobic synthesis of unsaturated fatty acid was compared between in vitro reactions by the fatty acid syntheses prepared from the mutant and parent strains. Amounts of unsaturated fatty acids synthesized from radio-labeled precursor were found to be almost the same in the both strains.(4)The activity of the fatty acid desaturase, the key enzyme in the aerobic mechanism, in the mutant strain was less than a half of that of the parent strain. Furthermore, the enzyme activity could not be induced in the mutant strain, when the cells were cultured in the medium comprised of peptone and saturated fatty acid.(5)The mutant strain exhibited much higher sensitivity to 3-decynoyl-Ncysteamine, an inhibitor of the anaerobic pathway, than the parent strain. Above results indicate that the both aerobic and anaerobic pathways are required for the growth of Pseudomonas E-3.