Difference in C3-C4 metabolism underlies tradeoff between growth rate and biomass yield in Methylobacterium extorquens AM1.

Yanfen Fu,Mary E Lidstrom,David A C Beck

doi:10.1186/s12866-016-0778-4

Yanfen Fu, Mary E Lidstrom + Show 1 more

Open Access

https://doi.org/10.1186/s12866-016-0778-4

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Journal: BMC microbiology	Publication Date: Jul 19, 2016
Citations: 11	License type: CC BY 4.0

Affiliation: University of Washington, Seattle University

Abstract

BackgroundTwo variants of Methylobacterium extorquens AM1 demonstrated a trade-off between growth rate and biomass yield. In addition, growth rate and biomass yield were also affected by supplementation of growth medium with different amounts of cobalt. The metabolism changes relating to these growth phenomena as well as the trade-off were investigated in this study. 13C metabolic flux analysis was used to generate a detailed central carbon metabolic flux map with both absolute and normalized flux values.ResultsThe major differences between the two variants occurred at the formate node as well as within C3–C4 inter-conversion pathways. Higher relative fluxes through formyltetrahydrofolate ligase, phosphoenolpyruvate carboxylase, and malic enzyme led to higher biomass yield, while higher relative fluxes through pyruvate kinase and pyruvate dehydrogenase led to higher growth rate. These results were then tested by phenotypic studies on three mutants (null pyk, null pck mutant and null dme mutant) in both variants, which agreed with the model prediction.ConclusionsIn this study, 13C metabolic flux analysis for two strain variants of M. extorquens AM1 successfully identified metabolic pathways contributing to the trade-off between cell growth and biomass yield. Phenotypic analysis of mutants deficient in corresponding genes supported the conclusion that C3–C4 inter-conversion strategies were the major response to the trade-off.Electronic supplementary materialsThe online version of this article (doi:10.1186/s12866-016-0778-4) contains supplementary material, which is available to authorized users.

Highlights

Two variants of Methylobacterium extorquens AM1 demonstrated a trade-off between growth rate and biomass yield
Cobalt is needed for vitamin B12 production used as cofactor for two enzymes involved in methylotrophy growth, methylmalonyl-CoA mutase (Mcm) and ethylmalonyl-CoA mutase (Ecm) in the ethylmalonyl-CoA pathway, and plays a role in strain fitness [8, 9, 11]
Extorquens AM1 for two strain variants as well as two cobalt levels Observations of growth rate differences prompted a more in-depth study of two M. extorquens AM1 strains, a parent strain from the laboratory of Mary Lidstrom (LL strain), and a strain that originated from the Lidstrom laboratory, but was carried in the laboratory of Julia Vorholt (VL strain) since 2001

Summary

Introduction

Two variants of Methylobacterium extorquens AM1 demonstrated a trade-off between growth rate and biomass yield. The metabolism changes relating to these growth phenomena as well as the trade-off were investigated in this study. With the development of transcriptomics, proteomics, metabolomics and fluxomics, studies on C1 metabolism in M. extorquens AM1 have recently been carried out using system approaches [5,6,7]. Recent studies have shown that cobalt is an important trace metal for methylotrophic growth in M. extorquens AM1. Cobalt is needed for vitamin B12 production used as cofactor for two enzymes involved in methylotrophy growth, methylmalonyl-CoA mutase (Mcm) and ethylmalonyl-CoA mutase (Ecm) in the ethylmalonyl-CoA pathway, and plays a role in strain fitness [8, 9, 11]. The effect of cobalt on the overall central carbon metabolism in M. extorquens AM1 remains unknown

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