Phenotypic characterization of Corynebacterium glutamicum under osmotic stress conditions using elementary mode analysis

Abstract

Corynebacterium glutamicum, a soil bacterium, is used to produce amino acids such as lysine and glutamate. C. glutamicum is often exposed to osmolality changes in its medium, and the bacterium has therefore evolved several adaptive response mechanisms to overcome them. In this study we quantify the metabolic response of C. glutamicum under osmotic stress using elementary mode analysis (EMA). Further, we obtain the optimal phenotypic space for the synthesis of lysine and formation of biomass. The analysis demonstrated that with increasing osmotic stress, the flux towards trehalose formation and energy-generating pathways increased, while the flux of anabolic reactions diminished. Nodal analysis indicated that glucose-6-phosphate, phosphoenol pyruvate, and pyruvate nodes were capable of adapting to osmotic stress, whereas the oxaloacetic acid node was relatively unresponsive. Fewer elementary modes were active under stress indicating the rigid behavior of the metabolism in response to high osmolality. Optimal phenotypic space analysis revealed that under normal conditions the organism optimized growth during the initial log phase and lysine and trehalose formation during the stationary phase. However, under osmotic stress, the analysis demonstrated that the organism operates under suboptimal conditions for growth, and lysine and trehalose formation.

Trends in bacterial trehalose metabolism and significant nodes of metabolic pathway in the direction of trehalose accumulation

“…Unfortunately, limited metabolic flux studies linked with trehalose biosynthesis were reported. Metabolic flux and elementary mode analysis in Corynebacterium glutamicum indicated increased flux towards trehalose formation and it was principle osmolyte in low dilution rate (Rajvanshi and Venkatesh, ; Wiitmann and Heinzle, ). In addition, carbon flux towards trehalose increased under oxidative stress after deleting transcription repressor McbR (Krömer et al ., ).…”

Metabolomic basis of laboratory evolution of butanol tolerance in photosynthetic Synechocystis sp. PCC 6803

“…Among them, NADPH is an important coenzyme participating in many cellular reactions, and their identification in tolerance-enhanced cells is also consistent with our previous proteomic analysis that found several NADPH-dependent enzymes, such as glycerol-3-phosphate dehydrogenase were responsive to exogenous butanol stress in Synechocystis [ 13 ]. Although most of other metabolites have never been reported for their roles in combating butanol stress, PEP as a glycolysis metabolite with a high-energy phosphate group has been reported with anti-oxidative properties [ 29 ], and responsive to osmotic stress in Corynebacterium glutamicum [ 30 ], while the changing levels of 3PG and R5P were found in plant under heat stress [ 31 ], and in Saccharomyces cerevisiae under acetic acid stress [ 32 ], respectively. In addition, ribose-5-phosphate isomerase that catalyzes the conversion between ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P) was recently found regulated under oxidative stress conditions in photosynthetic green algae Chlamydomonas reinhardtii [ 33 ].…”

Recent advances in elementary flux modes and yield space analysis as useful tools in metabolic network studies

“…In silico comparison of production in E.coli and yeast; knockout strategies are identified using constrained minimal cut sets Gruchattka et al (2013) Muconic acid production in E. coli and yeast (Rajvanshi and Venkatesh 2011), external stress-induced isobutanol production by Bacillus subtilis (Li et al 2012) and Clostridium acetobutylicum (Kumar et al 2014), or riboflavin production by Ashbya gossypii (Jeong et al 2015).…”