• Microbiology and Biotechnology Letters
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• v.39 no.1
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• pp.93-96
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• 2011

It has been shown that a nucleotide substitution at position 770 in Escherichia coli 16S rRNA, which is implicated in forming the evolutionary conserved B2c intersubunit bridge, has a detrimental effect on ribosome function. In order to isolate second-site revertants that complement ribosomes containing C770G, we performed a random mutagenesis of the 16S rRNA gene and selected clones that could produce more CAT protein translated by specialized ribosome. One of the clones contained two nucleotide substitutions at positions 569 and 904 (C569G and U904C) and these mutations partially complemented the loss of protein-synthesis ability caused by C770G. Further studies using the isolated revertant will provide information about which part of 16S rRNA is interacting with C770 and the consequence of the structure formed by these interactions in the process of protein synthesis.

• Journal of Microbiology and Biotechnology
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• v.28 no.11
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• pp.1916-1927
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• 2018

Corynebacterium glutamicum is an excellent platform for the production of amino acids, and is widely used in the fermentation industry. Most industrial strains are traditionally obtained by repeated processes of random mutation and selection, but the genotype of these strains is often unclear owing to the absence of genomic information. As such, it is difficult to improve the growth and amino acid production of these strains via metabolic engineering. In this study, we generated a complete genome map of an industrial L-valine-producing strain, C. glutamicum XV. In order to establish the relationship between genotypes and physiological characteristics, a comparative genomic analysis was performed to explore the core genome, structural variations, and gene mutations referring to an industrial L-leucine-producing strain, C. glutamicum CP, and the widely used C. glutamicum ATCC 13032. The results indicate that a 36,349 bp repeat sequence in the CP genome contained an additional copy each of lrp and brnFE genes, which benefited the export of L-leucine. However, in XV, the kgd and panB genes were disrupted by nucleotide insertion, which increase the availability of precursors to synthesize L-valine. Moreover, the specific amino acid substitutions in key enzymes increased their activities. Additionally, a novel strategy is proposed to remodel central carbon metabolism and reduce pyruvate consumption without having a negative impact on cell growth by introducing the CP-derived mutant $H^+$/citrate symporter. These results further our understanding regarding the metabolic networks in these strains and help to elucidate the influence of different genotypes on these processes.