Microbial Cycling of Methanethiol.

Hendrik Schäfer,Özge Eyice

doi:10.21775/cimb.033.173

Abstract

Methanethiol (MT) is an organic sulfur compound with a strong and disagreeable odour. It has biogeochemical relevance as an important compound in the global sulfur cycle, where it is produced as a reactive intermediate in a number of different pathways for synthesis and degradation of other globally significant sulfur compounds such as dimethylsulfoniopropionate, dimethylsulfide and methionine. With its low odour threshold and unpleasant smell, MT can be a significant cause of malodour originating from animal husbandry, composting, landfill operations, and wastewater treatment and is also associated with faeces, flatus and oral malodour (halitosis). A diverse range of microorganisms drives the production and degradation of MT, including its aerobic and anaerobic metabolism. MT producing and degrading organisms are known to be present in terrestrial, freshwater and marine environments but may also be important in association with plant and animal (including human) hosts. This chapter considers the role of MT as an intermediate of the global sulfur cycle and discusses current knowledge of microbial pathways of MT production and degradation.

Highlights

Methanethiol (MT), known as methylmercaptan, is a one-carbon organic sulfur compound with the formula CH3SH
As a product of decaying biomass, it can be found widely in the environment, for instance as a compound emitted from rotting fruit and vegetables but it is found in association with humans and animals where it is a component of the smell of faeces, flatus and can be associated with bad breath (NCBI Pubchem database, n.d.)
In a study primarily reporting carbonyl sulfide (COS) emissions from the Aegean Sea, MT concentrations detected at time zero in incubation experiments with natural seawater samples were in a range of 50-500 pM and it was suggested that MT was subject to photodegradation and could potentially be a precursor for COS photoproduction (Ulshöfer et al, 1996)

Summary

Introduction

Methanethiol (MT), known as methylmercaptan, is a one-carbon organic sulfur compound with the formula CH3SH. Environmental concentrations, production and degradation of MT Environmental concentrations of MT Only relatively few studies have measured MT concentrations in seawater, anoxic environments and industrial settings. Surface freshwater MT concentrations in the peat bog were 1-8 nM and in a similar range to those of H2S, DMS and CS2, demonstrating that MT contributes to emission of S from such freshwater environments (Lomans et al, 1997). In a study primarily reporting carbonyl sulfide (COS) emissions from the Aegean Sea, MT concentrations detected at time zero in incubation experiments with natural seawater samples were in a range of 50-500 pM and it was suggested that MT was subject to photodegradation and could potentially be a precursor for COS photoproduction (Ulshöfer et al, 1996). In addition to above mentioned photodegradation, the reaction of MT with sulfate, dissolved organic matter (DOM) and trace metals to form sulfate-DOM-metal complexes has been suggested as an abiotic degradation pathway (Kiene et al, 2000)

Biological Production of MT

Anaerobic mechanisms

Microbial degradation of MT

Aerobic mechanisms

Findings

Conclusions