Salanitro J P, Wegener W S
J Bacteriol. 1971 Nov;108(2):893-901. doi: 10.1128/jb.108.2.893-901.1971.
Mutants of Escherichia coli K-12 which grow on butyrate and valerate were studied with respect to uptake of these substrates. To utilize short-chain and medium-chain fatty acids, E. coli must synthesize the beta-oxidation enzymes constitutively. In addition, growth on the C(4) and C(5) acids requires a second mutation which permits entry of these substrates. At pH 5, both in the parent and mutant strains, butyrate and valerate penetrate as the undissociated acids but appear not to be activated and thus inhibit growth. At pH 7, the parent strain is not permeable to the anions, whereas the mutant concentrates these substrates. There appear to be two components of the uptake system, a nonspecific diffusion component and an energy-linked activating enzyme. Two mutant types which take up short-chain fatty acids are described. One synthesizes the uptake system constitutively and is inhibited by 4-pentenoate when cultured on acetate. In the other, the uptake system is inducible, and the strain is pentenoate-resistant when grown on acetate but pentenoate-sensitive when cultured on butyrate or valerate.
对在丁酸盐和戊酸盐上生长的大肠杆菌K-12突变体进行了关于这些底物摄取的研究。为了利用短链和中链脂肪酸，大肠杆菌必须组成型地合成β-氧化酶。此外，在C(4)和C(5)酸上生长需要第二个突变，该突变允许这些底物进入。在pH 5时，在亲本菌株和突变体菌株中，丁酸盐和戊酸盐均以未解离的酸形式渗透，但似乎未被激活，因此抑制生长。在pH 7时，亲本菌株对阴离子不可渗透，而突变体则浓缩这些底物。摄取系统似乎有两个组成部分，一个非特异性扩散成分和一个能量连接的激活酶。描述了两种摄取短链脂肪酸的突变体类型。一种组成型地合成摄取系统，在乙酸盐上培养时被4-戊烯酸盐抑制。另一种中，摄取系统是可诱导的，该菌株在乙酸盐上生长时对戊烯酸盐有抗性，但在丁酸盐或戊酸盐上培养时对戊烯酸盐敏感。
