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Current Projects

Methylated amine metabolism in the ocean

Methylated amine compounds (MAs) are ubiquitous in the ocean and play significant roles in marine nutrient cycling and atmospheric chemistry. MAs are involved in the formation of aerosols and neutralization of atmospheric acidity resulting from the oxidation of nitrogen- and sulfur-containing compounds. MAs also contribute to the "greenhouse effect" by the formation of nitrous oxide (N2O) and hydrogen cyanide (HCN) from their oxidation by hydroxyl radicals and ozone, and by being precursors for methane (CH4) produced by methanogens. Despite the global importance of marine MAs, modelling and quantifying their environmental impacts has been hindered by a paucity of data on the origins and sinks of these compounds. Microorganisms are known to use MAs as sources of energy and nutrients therefore affecting the concentrations of MAs in the ocean and hence fluxes across the air-sea interface; however, the identities of these key players and metabolic pathways remain largely unknown. The objective of this proposed research is to characterize the diversity and abundance of marine MA utilizers and to investigate the enzymology and regulation of MA-metabolizing pathways using model marine microorganisms. This research will test the hypothesis that MAs are used as a carbon (C) source by specialized methylotrophs (bacteria that use one-carbon (C1) compounds) in the ocean, and that diverse marine microorganisms can metabolize MAs as a source of nitrogen (N).

Funding: NERC 2010-2013

Methylated amine production in the marine environment

Quaternary amines (QAs) such as glycine betaine (GBT) are ubiquitous in marine organisms. GBT is used by marine organisms as a compatible solute in response to changes in environmental conditions, such as increasing salinity, because GBT does not interfere with cell metabolism. QA compounds are frequently released into the ocean ecosystems due to environmental changes, such as viral attack and grazing. The degradation of these compounds, especially in intertidal coastal areas, contributes significantly to the production of climate-active trace gases. These include the potent greenhouse gas methane and volatile methylated amines, which are thought to be involved in cloud formation in the marine environment.

Coastal sediments are estimated to contribute approximately 75% of the global oceanic methane emissions (8-13 Tg per year) and much of this is likely to be derived from the degradation of QAs. Although we know that microorganisms are mainly responsible for the degradation of GBT to methane and volatile methylamines, we know little about the genes and enzymes involved in the degradation pathway. Furthermore, the identity of those microorganisms responsible for the transformation has not yet been determined. Our current knowledge of these two aspects remains speculative, at least partially due to the lack of definitive research.

This NERC-funded project aims to fill in this major gap in our knowledge of marine carbon cycle. Using cultivated model microorganisms, we aim to define the key genes and the encoding enzymes in the anaerobic degradation of GBT. Using molecular ecology techniques and the resultant data from the study of the model microorganisms, we aim to further determine the key microbial players involved in the anaerobic production of methane and methylamines from GBT in the marine environment.

Funding: NERC 2011-2014

Project collaborators: Dr KJ Purdy (Warwick), Prof JC Murrell (Warwick), Dr SD Archer (Plymouth Marine Laboratory), Dr RL Airs (Plymouth Marine Laboratory)

For more information, please contact Y Chen (