L-glutamate production by lysozyme-sensitive Corynebacterium glutamicum ltsA mutant strains.
L-glutamate production by lysozyme-sensitive Corynebacterium glutamicum ltsA mutant strains.
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DOI：
10.1186/1472-6750-1-9
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发表时间：
2001
影响因子：
3.5
通讯作者：
Nagai K
中科院分区：
文献类型：
--
作者：
Hirasawa T;Wachi M;Nagai K
棒状杆菌是一种非致病的棒状细菌，谷氨酸棒杆菌最初是作为一种L谷氨酸产生菌分离出来的，现在用于发酵生产各种氨基酸。谷氨酸杆菌ltsA基因的突变导致对溶菌酶的敏感性、温度敏感型生长和L谷氨酸的产生。对经N-甲基-N‘-硝基-N-亚硝胺诱变后分离到的8株溶菌酶敏感突变株的特性进行了研究。与野生型ltsA基因的互补分析和ITSA区的DNA测序表明，4个突变体的ltsA基因发生了突变。其中，两个突变体表现出对温度敏感的生长并在较高温度下过量生产L-谷氨酸，以及先前报道的ltsA突变体。另外两个突变体表现出耐温生长：一个错义突变体在一定程度上产生L谷氨酸，而另一个无义突变体不产生。这两个突变体尽管引入了导致在野生型背景中对温度敏感的生长的ltsA：：Kan突变，但仍保持耐温性。这些结果表明，由ltsA突变引起的缺陷是谷氨酸杆菌对温度敏感的生长和L-谷氨酸过量生产的原因。这两个耐高温突变体似乎携带了抑制基因突变，使细胞对温度产生抗性，并消除了L-谷氨酸的过量生产。
A non-pathogenic species of coryneform bacteria, Corynebacterium glutamicum, was originally isolated as an L-glutamate producing bacterium and is now used for fermentative production of various amino acids. A mutation in the C. glutamicum ltsA gene caused susceptibility to lysozyme, temperature-sensitive growth, and L-glutamate production. The characteristics of eight lysozyme-sensitive mutants which had been isolated after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis were examined. Complementation analysis with the cloned wild-type ltsA gene and DNA sequencing of the ItsA region revealed that four mutants had a mutation in the ltsA gene. Among them, two mutants showed temperature-sensitive growth and overproduced L-glutamate at higher temperatures, as well as the previously reported ltsA mutant. Other two showed temperature-resistant growth: one missense mutant produced L-glutamate to some extent but the other nonsense mutant did not. These two mutants remained temperature-resistant in spite of introduction of ltsA::kan mutation that causes temperature-sensitive growth in the wild-type background. These results indicate that a defect caused by the ltsA mutations is responsible for temperature-sensitive growth and L-glutamate overproduction by C. glutamicum. The two temperature-resistant mutants seem to carry suppressor mutations that rendered cells temperature-resistance and abolished L-glutamate overproduction.