Microbial degradation of DMSO in the marine environment

Lead Research Organisation: Plymouth Marine Laboratory
Department Name: Plymouth Marine Lab

Abstract

Dimethylsulfoxide (DMSO) is a chemical with a wide range of applications. It is a widely used solvent, for instance in pharmaceutical applications, and a waste product of the paper milling industry. It also occurs naturally in a range of fruits, like raspberries, and vegetables. However, DMSO is also a compound that is part of the natural sulphur cycle. Sulphur is an essential element for all life, and in its organic form is a component of all proteins such as the amino acids cysteine and methionine. DMSO is an organic sulphur compound found everywhere in our oceans, and is produced by a number of natural biological and chemical processes.

DMSO is important because it is both a source and a sink for a climate-cooling gas called dimethyl sulfide (DMS). DMS is a component of the smell of the seaside. Around 300 million tons of DMS are made each year by marine microorganisms. Some of this DMS is released into the atmosphere above the oceans, where it reacts in air to compounds that seed clouds, which is suggested influences weather and climate. When it rains, sulphur compounds are deposited back into the soils of our continents. However the majority of the DMS formed in the oceans is thought not to be released to the atmosphere, but rather to be converted to DMSO, and thus stays in seawater. However what happens to this DMSO largely remains a mystery, but it has been suggested that it can be converted back to DMS, and thus be a source for climatically relevant sulphur emissions to the atmosphere. What we do know is that DMSO is commonly the most abundant organic sulphur compound in the oceans, and represents a major pool of the essential life elements sulphur and carbon.

The research to be carried out in this proposal is focused on firstly finding out what happens to DMSO in seawater. We have some preliminary evidence, found using radiolabelled DMSO as a tracer, that it is degraded by microorganisms who both incorporate its carbon into their biomass for growth purposes, and degrade it to carbon dioxide. However we also think that perhaps other microbes could transfer DMSO back to DMS, and even use its sulphur as an essential element. Therefore in this proposal we have designed a series of different tracer experiments to find out which processes occur in our seas, how important they are and how fast they happen. We will also put names to the microbes using DMSO, and find out which metabolic pathways are involved. We will study these microbial DMSO transformations in the English Channel at a station called L4. This station is sampled weekly as part of the Western Channel Observatory which is coordinated by Plymouth Marine Laboratory. This is a long-standing time series site for which data on phytoplankton diversity, abundance, temperature, nutrient dynamics and bacterial diversity are also measured and will be made freely available to this project (http://www.westernchannelobservatory.org.uk).

Given the important role of DMSO and its related compound DMS, identifying the populations and pathways of DMSO removal from seawater will provide key information that will improve our future understanding of the complex sulphur cycle and how it influences our climate.

Planned Impact

see Lead proposal document

Publications

10 25 50
 
Description 1) First results showing that coastal marine microbes utilise carbon from DMSO for both growth and energy (assimilation and dissimilation). However, rates of DMSO dissimilation to CO2 were up to 2 orders of magnitude higher than rates of assimilation. 2) Microbial oxidation of DMSO carbon to CO2 could be a signfiicant loss process for dissolved DMSO in marine waters (new knowledge). 3) Turnover times for dissolved DMSO range between 0.6-1.9 days.
Exploitation Route Adds new knowledge & experimental evidence of marine organic S cycle, specifically pathways and rates of DMSO losses.
Sectors Environment

 
Description NERC Discovery Science July 2017 submission round
Amount £647,921 (GBP)
Funding ID NE/R010382/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 05/2018 
End 05/2021
 
Title Application of 14C labelled DMSO 
Description The use of 14C labelled DMSO has been trialled and used to determine the amount of carbon from DMSO that marine microbes are utilising as either a source for growth (assimilation) or a source of energy (dissimilation). This methodology has been added to stable tracer methods to determine the sources and sinks of DMSO in seawater during a time series at a coastal long term monitoring station, L4 in the western English Channel. There is a resulting time series for 2014 and 2016. 
Type Of Material Biological samples 
Year Produced 2016 
Provided To Others? Yes  
Impact Understanding the sinks of DMSO in seawater. A manuscript has been prepared and submitted. 
 
Title WCO L4 surface DNA samples 
Description DNA samples were collected throughout 2014 and 2016 for collaborators at Warwick University to; 1) identify DMSO-assimilating microorganisms, 2) identify the functional diversity of DMSO degradation genes and 3) understand seasonal variability at station L4 
Type Of Material Biological samples 
Year Produced 2016 
Provided To Others? Yes  
Impact Samples are still being analysed. 
 
Title 14C tracer experiments station L4 
Description 14C2 - DMSO tracer being used to determine loss rates due to a) dissimilation to CO2 for microbial energy generation and b) microbial assimilation for growth 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? No  
Impact Annual surveys at station L4 undertaken in 2014 and 2016. Data will be submitted to BODC once it has been quality controlled. DOI will then follow. 
 
Title Seawater concentration of DMSO, DMS, DMSP database for 2014 and 2016 completed. 
Description Approximately annual surveys of the changes in concentrations of DMSO, DMS and DMSP have been undertaken in 2014 and 2016 on surface (10m) and deep (50m) water samples. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
Impact Data has been provided to collaborators at Warwick University. Data has been sent to BODC. Waiting for DOI. 2014 data doi:10.5285/77294815-9c69-338b-e053-6c86abc070db 2016 data doi:10.5285/77294815-9c6a-338b-e053-6c86abc070db 
URL https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/77294815-9c6a-338b-e053-6c86abc...
 
Title Stable tracer experiments for determining DMSO loss processes Station L4 
Description Three stable tracers were used (13C-DMSO, d3- DMS, d6-DMSP) to determine the biological consumption, net and gross production and turnover times of DMS, DMSP and DMSO in surface waters of station L4, WCO. 2014 and 2016 datasets. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
Impact Detailed time series in 2016 (with some preliminary data from 2014). Data has been submitted to BODC WCO database. Currently waiting for DOI from BODC.