One-carbon Substrates Research Articles

Metabolism of One-Carbon Compounds by Chemotrophic Anaerobes

Publisher Summary This chapter focuses on the metabolism of one-carbon (C1) compounds chemotrophic anaerobes. C1-metabolizing species possess novel physiologies that are distinctive in many ways from the autotrophic and heterotrophic microorganisms, which seemingly are more widespread in the microbial world. C1 compounds refer to any oxidizable one-carbon substrate that contains carbon-bound electrons. A C1 substrate differs noticeably from the C1 compound carbon dioxide because, in addition to being able to be reduced or assimilated, it can also be oxidized and can provide electrons for use in energy metabolism or cell synthesis. The term “chemotrophic anaerobe” refers to any obligately non-oxygen-catabolizing microbial species whose growth is solely dependent on the generation of metabolic energy from chemical substrates. The chapter examines the microbial physiology that accounts for unicarbonotrophy in anaerobes. The C1 metabolites enter anaerobic ecosystems of the biosphere either as pollutants from aerobic environments, volcanic or deep subsurface emanations, or via chemical transformation reactions performed by anaerobic microorganisms. The formation of C1 metabolites often necessitates their removal in biological elemental cycles because they can accumulate and alters normal carbon and electron flow within a cell, or becomes toxic and result in cell death.

Alkylation of an enzyme in the methane-forming system of [formula omitted

One-carbon compounds occur abundantly at all oxidation levels between methane and carbon dioxide. Methane occurs in coal and oil deposits and is also evolved on a large scale as an end-product of many fermentations. Carbon dioxide is also abundantly present in the atmosphere, in natural waters, and as carbonates in the earth. A considerable number of micro-organisms have developed the ability to utilize such compounds as carbon or energy sources. This chapter examines these micro-organisms and the biochemical problems, which are posed by energy transduction and biosynthesis of cell constituents from the one-carbon substrate. It explains the description and physiology of one-carbon-utilizing micro-organisms along with their energy metabolism and carbon assimilation. The utilization of one-carbon compounds is largely confined to prokaryotic organisms. Many enzymes that catalyze the oxidation of one-carbon compounds at a variety of oxidation levels are also extensively studied. The chapter also considers mechanisms that offer a solution to the problem of net biosynthesis from one-carbon units at reduction levels ranging from carbon dioxide to methane.