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Title: Microbial ecological approaches used to investigate DMSP production in Stiffkey salt marsh sediments
Author: Williams, Beth
ISNI:       0000 0004 7962 7796
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2019
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Dimethylsulfoniopropionate (DMSP) and its catabolite dimethyl sulfide (DMS) are key marine nutrients, with roles in global sulfur cycling, atmospheric chemistry, signalling and, potentially, climate regulation. In the surface layer of salt marsh sediments DMSP concentrations are > three orders of magnitude higher than in the overlying seawater, an environment usually touted as being the most important site for DMSP production. A third of bacterial isolates from salt marsh pond sediment were found to produce DMSP (up to 160 nmol/mg protein) and, furthermore, many more novel DMSP-producing bacteria were identified after performing enrichment microcosm experiments for bacterial DMSP production. Most DMSP-producing isolates contained the dsyB gene, but several (Alteromonas, Marinobacter and Novosphingobium), lacked this reporter gene for DMSP synthesis. A Novosphingobium sp. MBES04 isolate produced DMSP via a novel bacterial methionine methylation pathway, and a bacterial methionine methyltransferase 'mmtN' gene was discovered. BLASTp results revealed a diverse range of bacteria that contain it, and both alphaproteobacteria and actinobacteria within that group were shown to produce DMSP. DMSP-producing bacteria, mmtN abundance and dsyB transcripts were present in all tested seawater samples and Tara Oceans bacterioplankton datasets, but were far more abundant in marine surface sediment. Thus, we propose that surface marine sediments are environments with high DMSP productivity and that heterotrophic bacteria are likely important producers in these environments.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available