Unique Central Carbon Metabolic Pathways and Novel Enzymes in Phototrophic Bacteria Revealed by Integrative Genomics, 13C-based Metabolomics and Fluxomics

Abstract

Abstract:Photosynthesis is the process to convert solar energy to biomass and biofuels, which are the only major solar energy storage means on Earth. To satisfy the increased demand for sustainable energy sources, it is essential to understand the process of solar energy storage, that is, the carbon metabolism in photosynthetic organisms. It has been well-recognized that one bottleneck of photosynthesis is carbon assimilation. In this report, we summarize our recent studies on the carbon metabolism pathways of several types of photosynthetic bacteria, including aerobic anoxygenic phototrophic proteobacteria, green sulfur bacteria, heliobacteria and cyanobacteria, using physiological studies, transcriptomics, enzyme assays, 13 C-based metabolomics and fluxomics. Our studies have revealed several unique and/or significant central carbon metabolic pathways and novel enzymes that operate in these phototrophs, quantified CO 2 assimilation pathways operative during mixotrophic cultivation conditions, and also suggested evolutionary links between photosynthetic and non-photosynthetic organisms.

13C-assisted metabolic flux analysis to investigate heterotrophic and mixotrophic metabolism in Cupriavidus necator H16

“…The expression of maeB and malate dehydrogenase gene mdh is upregulated in trioleate-utilizing cultures (Brigham et al 2010 ), which complements the flux in heterotrophic growth with glycerol. Flux is predicted through PEP carboxykinase (PEPCK) in glycerol-utilizing cultures complementing our RT-PCR results and literature reports, suggesting that the production of oxaloacetate (OAA) by carboxylation of phosphoenolpyruvate (PEP) is critical for the oxidative TCA cycle when it is running low (Tang et al 2013 ).…”