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

不饱和脂肪酸营养缺陷型突变株是从嗜冷菌假单胞菌中分离到的。菌株E-3，对不饱和脂肪酸有两种不同的作用机制。为了研究突变株的生理生化特性，对突变株进行了生理生化研究：(1)突变株的生长速度和菌体质量依赖于添加不饱和脂肪酸(如棕榈油酸或油酸)的浓度，当添加0.01%的油酸时，突变株的生长速度几乎与亲本相同。(2)突变株在含油酸的培养基上生长的磷脂中，油酸是主要的不饱和脂肪酸组成。在相同的培养条件下，亲本菌株中主要的不饱和脂肪酸是顺式菌酸，而不是油酸。研究发现，出发菌株磷脂的脂肪酸组成不受外源不饱和脂肪酸的影响。(3)通过突变菌株和亲本菌株合成脂肪酸的体外反应比较了不饱和脂肪酸的厌氧合成。从放射性标记前体合成的不饱和脂肪酸在两个菌株中几乎相同。(4)突变菌株中好氧机制中的关键酶脂肪酸去饱和酶的活性不到亲本菌株的一半。此外，突变菌株在含有蛋白胨和饱和脂肪酸的培养液中不能诱导细胞产生酶活性。(5)突变菌株对厌氧途径的抑制剂3-癸基-N-半胱胺的敏感性明显高于出发菌株。上述结果表明，假单胞菌E-3的生长既需要好氧途径，也需要厌氧途径。

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.