Abstract
ABSTRACT Currently, the mechanism of temperature-sensitive production of glutamate in Corynebacterium glutamicum has not been clarified. We first found the murA and murB genes were potentially related to temperature-sensitive secretion of glutamate, which were not existed in a temperature-sensitive mutant. When replenishing murA or/and murB in the mutant, the temperature sensitivity was weakened. While, their knockout in a wild-type strain resulted in temperature-sensitive secretion of glutamate. Peptidoglycan analysis showed that deletion of murA and murB decreased the peptidoglycan synthesis. Comparative metabolomics analysis suggested that the variation in cell wall structure resulted in decreased overall cellular metabolism but increased carbon flow to glutamate synthesis, which was a typical metabolism pattern in industrial temperature-sensitive producing strains. This study clarifies the mechanism between murA and murB deletion and the temperature-sensitive secretion of glutamate in C. glutamcium, and provides a reference for the metabolic engineering of cell wall to obtain increased bioproduction of chemicals.
Highlights
The Gram-positive soil bacterium Corynebacterium glutamicum was originally discovered about 60 years ago and is well known as an excellent producer of glutamate [1]
The results of scanning electron microscopy and gene analysis showed that murA and murB genes were the first two genes in the pathway of peptidoglycan synthesis. Their deletion would inhibit the synthesis of peptidoglycan, affecting cell wall synthesis and changing cell permeability
Fermentation experiments and metabolomics studies have confirmed that the deletion of murA and murB gene can inhibit the growth of bacteria, increase cell permeability, and effectively export intracellular glutamate, so that the intracellular glutamate level can be maintained at a low level, thereby increasing the driving force of glutamate synthesis and promoting glutamate secretion
Summary
The Gram-positive soil bacterium Corynebacterium glutamicum was originally discovered about 60 years ago and is well known as an excellent producer of glutamate [1]. With the development of biotechnology, C. glutamicum has been successfully engineered to serve as a versatile workhorse for industrial bioproduction of various chemicals [2,3,4]. This bacterium has been used to produce more than 4 million tons of diverse amino acids per year, as well as a wide range of other natural and non-natural products, which are used as feed additives, nutritional supplements, pharmaceutical intermediates, biofuels, and polymer building blocks [5].
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