Anaerobic microbial methanol conversion in marine sediments

Abstract

Methanol is an ubiquitous compound that plays a role in microbial processes as a carbon and energy source, intermediate in metabolic processes or as end product in fermentation. In anoxic environments, methanol can act as the sole carbon and energy source for several guilds of microorganisms: sulfate-reducing microorganisms, nitrate-reducing microorganisms, acetogens and methanogens. In marine sediments, these guilds compete for methanol as their common substrate, employing different biochemical pathways. In this review, we will give an overview of current knowledge of the various ways in which methanol reaches marine sediments, the ecology of microorganisms capable of utilizing methanol and their metabolism. Furthermore, through a metagenomic analysis, we shed light on the unknown diversity of methanol utilizers in marine sediments which is yet to be explored.

Fig. 1

Methanol degradation pathways as outlined in this review. A. Respiratory methanol oxidation. Abbreviations: xoxF, lanthanide‐dependent methanol dehyrdogenase; MxA, calcium‐dependent methanol dehydrogenase; RuMP pathway, ribulose monophosphate pathway for carbon fixation; WLP, Wood–Ljungdahl pathway for carbon fixation. B. Acetogenesis pathway. Abbreviations: THF, tetrahydrofolic acid; CODH/ACs, carbon monoxide dehydrogenase/Acetyl‐coA synthetase C. methanogenesis; MT, methyl‐transferase 1; CoM, co‐enzyme M; H ₄ MPT, tetrahydromethanopterin; Mcr, methyl‐coenzyme M reductase; MFR, methanofuran. [Color figure can be viewed at wileyonlinelibrary.com]

Fig. 2

Metagenomic mining heatmap. Red indicates presence, blue absence. Gene abbreviations: xoxF, lanthanide dependent methanol dehydrogenase F; mtaA, methanol methyltransferase A; mtaB, methanol methyltransferase B; mtaC, methanol methyltransferase C; fdhA, formaldehyde dehydrogenase A; pest, pectin methanolesterase. Each cluster denotes 50 metagenomes screened. [Color figure can be viewed at wileyonlinelibrary.com]