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We previously reported the extracellular production of antibody fragment Fab by Corynebacterium glutamicum. In the course of searching for genes which improve the secretion efficiency of Fab, we coincidentally found that the final growth increased significantly when the NCgl2986 gene encoding an amidase-like protein was overexpressed. This effect was observed when cells were grown on the production medium MMTG, which contains high concentrations of glucose and neutralizing agent CaCO3, but not on MMTG without CaCO3 or Lennox medium. Not only turbidity but also dry cell weight was increased by NCgl2986 overexpression, although the growth rate was not affected. It was recently reported that the Mycobacterium tuberculosis homolog Rv3915 functions as an activator of MurA protein, which catalyzes the initial step of peptidoglycan synthesis. Growth promotion was also observed when the MurA protein was overproduced. His-tagged NCgl2986 protein was purified, but its peptidoglycan hydrolyzing activity could not be detected. These results suggest that NCgl2986 promotes cell growth by activating the peptidoglycan synthetic pathway.

Corynebacterium glutamicum is used for the industrial production of various metabolites, including L-glutamic acid and L-lysine. With the aim of understanding the post-transcriptional regulation of amino acid biosynthesis in this bacterium, we investigated the role of RNase E/G in the degradation of mRNAs encoding metabolic enzymes. In this study, we found that the cobalamin-independent methionine synthase MetE was overexpressed in ΔrneG mutant cells grown on various carbon sources. The level of metE mRNA was also approximately 6- to 10-fold higher in the ΔrneG mutant strain than in the wild-type strain. A rifampicin chase experiment showed that the half-life of metE mRNA was approximately 4.2 times longer in the ΔrneG mutant than in the wild-type strain. These results showed that RNase E/G is involved in the degradation of metE mRNA in C. glutamicum.

Single and multiple mutations in the mreB, mreC, and mreD genes of Escherichia coli, which are involved in rod shape determination and the accompanied change in the cell's mecillinam resistance, caused an increase in the quantity of septum-peptidoglycan synthetase penicillin-binding protein (PBP)-3, and more general peptidoglycan synthetase PBP-1B. The mreD mutant, but not the mreB and mreC mutants, showed a decreased growth which could be suppressed by deletion of the total mreBCD-orfEF area on the chromosome. The mre mutations additionally caused a complex nature increase/decrease of several other cytoplasmic and membrane protein quantities. These results suggest that the mreB, mreC, and mreD genes are involved in a complex regulatory mechanism in the process of cell growth, division and shape determination.

The murG gene located in the mra region at 2min on the Escherichia coli chromosome map was found to be responsible for UDP-GlcNAc: undecaprenyl-pyrophosphoryl-N-acetylmuramoyl-pentapeptide N-acetylglucosaminyl transferase activity in lipid cycle reactions of cell wall peptidoglycan synthesis. murG was concluded to be the structural gene for this enzyme from the following findings: (1) Expression of GlcNAc-transferase activity by the murG gene seemed to be thermosensitive when the chromosome carried an amber mutation in murG and a thermosensitive sup mutation. (2) Overproduction of the murG product caused an increase of GlcNAc-transferase activity. Incidentally, chemically phosphorylated polyprenol was shown to function as a carrier in lipid cycle reactions in peptidoglycan synthesis in E. coli.

Determination of nucleotide sequence of a 2.8kb DNA fragment involving the murG and murC genes has completed the sequencing of the total 12kb mra region at 2min on the Escherichia coli chromosome map, which functions in the growth and division of the cell. Product proteins of the genes in the mra region have also been identified, of which the MurC and MurG proteins are reported here. Considerable homologies were found in the deduced amino acid sequences of four ligases, products of the murC, murD, murE and murF genes in the mra region. These synthesize UDP-N-acetylmuramyl-pentapeptide from UDP-N-acetylmuramic acid in peptidoglycan synthesis. The MurG protein, also involved in the cell growth of E. coli, showed considerable homology of the deduced amino acid sequence with that of a peptide coded for by an open reading frame in the spoVE-ftsZ region of the B. subtilis chromosome.