L-glutamate production by lysozyme-sensitive Corynebacterium glutamicum ltsA mutant strains.
BACKGROUND
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.


RESULTS
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.


CONCLUSIONS
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.
Hirasawa
T
T
Department of Bioengineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Japan. thirasaw@bio.titech.ac.jp
Wachi
M
M
Nagai
K
K
D003352:Corynebacterium / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D004252:DNA Mutational Analysis; D005798:Genes, Bacterial / Q000235:genetics*; D005816:Genetic Complementation Test; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000096:biosynthesis*; D009113:Muramidase / Q000378:metabolism*; D009154:Mutation / Q000235:genetics*; D013489:Suppression, Genetic / Q000235:genetics; D013696:Temperature
D018698:Glutamic Acid; D009113:Muramidase; D005947:Glucose