Genome-scale revealing the central metabolic network of the fast growing methanotroph Methylomonas sp. ZR1

Methylomonas sp. ZR1 was an isolated new methanotrophs that could utilize methane and methanol growing fast and synthesizing value added compounds such as lycopene. In this study, the genomic background and the expression pattern for the central metabolic pathways of ZR1 with methane and methanol as carbon sources were analyzed. Complete EMP, ED, PP and TCA pathway were proved to exist and express in ZR1. The ppi-dependent EMP enzyme and complete TCA cycle efficiently produce energy and reduce power for the growth of ZR1,which might be responsible for its fast growth. Lower TCA cycle activity might be responsible for the worse growth of ZR1 with methanol under 30?. Several important metabolic pathways were found correlating with carbon sources. Metabolism of formaldehyde was proved to be a key nod that may be responsible for the carbon conversion efficiency in ZR1. The higher expression level of the formaldehyde assimilation genes in comparison with the catabolism genes might be responsible for the higher carbon conversion efficiency of ZR1 from methane than methanol. Meanwhile, the flexible nitrogen and carotene metabolism related with the carbon substrates were also investigated in ZR1. Nitrogenase genes in ZR1 were found to be highly expressed with methane as carbon sources even though enough nitrate existed in the medium. Transcript level competition between the C40 and C30 metabolic genes might be responsible for the different categories of carotenoids pigments of ZR1 synthesized from the two kinds of C1 substrates.