Anaerobic quaternary amine degradation: from single bacterium to salt marsh ecosystem.

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 timely proposal 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.

The work will generate novel knowledge about our understanding of microbial GBT transformations and will therefore fill in a serious gap in our knowledge of the marine carbon cycle.

This project addresses fundamental questions relating to the marine carbon cycle and greenhouse emissions from the natural environments, both of which are crucial for our understanding of global biogeochemical cycles and in the drive for a more sustainable future. The work is therefore of the utmost relevance to NERC's strategic aims, particularly the Biodiversity Science and Climate Change themes. The proposed research will have considerable impact on the following communities, the Environmental Agency, policy-makers and the wider public.

The Environmental Agency has launched schemes and activities in the last five years to protect the salt marsh ecosystems and also to create around 500 hectares of salt marsh along the Essex and Suffolk coastlines. However, whether these activities will affect local emissions of climate-active trace gases is uncertain. Our research can contribute to the decision making by the Environmental Agency and inform environmental policy making decisions.
The other beneficiaries of knowledge arising from this research will be policy-makers. They will be alerted to the positive and negative impacts of salt marsh ecosystems, which contribute not only to global warming (by releasing methane, a powerful greenhouse gas) but also potentially to global cooling (by releasing volatile small amines which are involved in aerosol formation).

Since our research has immediate relevance to climate and marine biology, it will be of interest to the wider public. People are always interested in scientific topics related to climate and marine life, and these two aspects of this type of research will always receive considerable attention in the media.

A variety of methods will be used to engage with the end-users, including workshops, a detailed website, publications in popular magazines such as Planet Earth, and visits and exhibitions at local schools. One of the things that we are keen to do is to have end user opinion at very early stages of our research. We consider that engagement of end users from the very early stages of the project will also benefit our research and help to formulate proper sampling activities during the research programme. For example, a workshop engaging the Environmental Agency will be set up in month 1 so that any concerns and questions from the Environmental Agency can then be defined and taken into account later on. On the website that we will set up from Month 1, we will have an online feedback form so that any queries from the wider public can be monitored and answered promptly.