Growth promotion in Corynebacterium glutamicum by overexpression of the NCgl2986 gene encoding a protein homologous to peptidoglycan amidases

Abstract

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 Myco-bacterium 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 sug-gest that NCgl2986 promotes cell growth by acti-vating the peptidoglycan synthetic pathway.