All living organisms share similar reactions within their central metabolism to provide precursors for all essential building blocksand reducing power. To identify whether alternative metabolic routes of glycolysis ca...All living organisms share similar reactions within their central metabolism to provide precursors for all essential building blocksand reducing power. To identify whether alternative metabolic routes of glycolysis can operate in E. coli, we complementarilyemployed in silico design, rational engineering, and adaptive laboratory evolution. First, we used a genome-scale model andidentified two potential pathways within the metabolic network of this organism replacing canonical Embden-Meyerhof-Parnas(EMP) glycolysis to convert phosphosugars into organic acids. One of these glycolytic routes proceeds via methylglyoxal andthe other via serine biosynthesis and degradation. Then, we implemented both pathways in E. coli strains harboring defectiveEMP glycolysis. Surprisingly, the pathway via methylglyoxal seemed to immediately operate in a triosephosphate isomerasedeletion strain cultivated on glycerol. By contrast, in a phosphoglycerate kinase deletion strain, the overexpression ofmethylglyoxal synthase was necessary to restore growth of the strain. Furthermore, we engineered the “serine shunt” whichconverts 3-phosphoglycerate via serine biosynthesis and degradation to pyruvate, bypassing an enolase deletion. Finally, toexplore which of these alternatives would emerge by natural selection, we performed an adaptive laboratory evolution studyusing an enolase deletion strain. Our experiments suggest that the evolved mutants use the serine shunt. Our study reveals theflexible repurposing of metabolic pathways to create new metabolite links and rewire central metabolism.展开更多
文摘All living organisms share similar reactions within their central metabolism to provide precursors for all essential building blocksand reducing power. To identify whether alternative metabolic routes of glycolysis can operate in E. coli, we complementarilyemployed in silico design, rational engineering, and adaptive laboratory evolution. First, we used a genome-scale model andidentified two potential pathways within the metabolic network of this organism replacing canonical Embden-Meyerhof-Parnas(EMP) glycolysis to convert phosphosugars into organic acids. One of these glycolytic routes proceeds via methylglyoxal andthe other via serine biosynthesis and degradation. Then, we implemented both pathways in E. coli strains harboring defectiveEMP glycolysis. Surprisingly, the pathway via methylglyoxal seemed to immediately operate in a triosephosphate isomerasedeletion strain cultivated on glycerol. By contrast, in a phosphoglycerate kinase deletion strain, the overexpression ofmethylglyoxal synthase was necessary to restore growth of the strain. Furthermore, we engineered the “serine shunt” whichconverts 3-phosphoglycerate via serine biosynthesis and degradation to pyruvate, bypassing an enolase deletion. Finally, toexplore which of these alternatives would emerge by natural selection, we performed an adaptive laboratory evolution studyusing an enolase deletion strain. Our experiments suggest that the evolved mutants use the serine shunt. Our study reveals theflexible repurposing of metabolic pathways to create new metabolite links and rewire central metabolism.
