Affiliation:
1. Institute of Microbiology, ETH Zurich, Zurich, Switzerland
2. Department of Microbiology, University of Washington, Seattle, Washington, USA
Abstract
ABSTRACT
Oxalate catabolism is conducted by phylogenetically diverse organisms, including
Methylobacterium extorquens
AM1. Here, we investigate the central metabolism of this alphaproteobacterium during growth on oxalate by using proteomics, mutant characterization, and
13
C-labeling experiments. Our results confirm that energy conservation proceeds as previously described for
M. extorquens
AM1 and other characterized oxalotrophic bacteria via oxalyl-coenzyme A (oxalyl-CoA) decarboxylase and formyl-CoA transferase and subsequent oxidation to carbon dioxide via formate dehydrogenase. However, in contrast to other oxalate-degrading organisms, the assimilation of this carbon compound in
M. extorquens
AM1 occurs via the operation of a variant of the serine cycle as follows: oxalyl-CoA reduction to glyoxylate and conversion to glycine and its condensation with methylene-tetrahydrofolate derived from formate, resulting in the formation of C3 units. The recently discovered ethylmalonyl-CoA pathway operates during growth on oxalate but is nevertheless dispensable, indicating that oxalyl-CoA reductase is sufficient to provide the glyoxylate required for biosynthesis. Analysis of an oxalyl-CoA synthetase- and oxalyl-CoA-reductase-deficient double mutant revealed an alternative, although less efficient, strategy for oxalate assimilation via one-carbon intermediates. The alternative process consists of formate assimilation via the tetrahydrofolate pathway to fuel the serine cycle, and the ethylmalonyl-CoA pathway is used for glyoxylate regeneration. Our results support the notion that
M. extorquens
AM1 has a plastic central metabolism featuring multiple assimilation routes for C1 and C2 substrates, which may contribute to the rapid adaptation of this organism to new substrates and the eventual coconsumption of substrates under environmental conditions.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
31 articles.
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