Dimethyl sulfide

Event Date: 
Wednesday, April 29, 2015 - 19:00 - 19:45
Institution: 
University of Southern California
Title: 

Bridging the gap between functional genes and biogeochemistry: a DMSP case study

Abstract: 

A large fraction of the surface ocean food web is active in producing and cycling both dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS).  In addition to the potential climatic significance of DMS production, the role that these compounds play in mediating ecosystem dynamics remains unknown.  An interdisciplinary dataset of biological, chemical and physical measurements was used to test current hypotheses of the role of light and carbon supply in regulating upper-ocean sulfur cycling in oligotrophic regions. Our results suggest that UV-A radiation dose plays an important role in both phytoplankton DMS production and bacterial DMSP degradation. We suggest a modified ‘bacterial switch’ hypothesis where the prevalence of different bacterial DMSP degradation pathways is regulated by a complex set of factors including carbon supply, temperature, and UV-A dose. Finally, numerical models of varying complexity were used to link genetic and enzyme data to biogeochemical rates.

JAMS attendees started off the night well lubricated thanks to the free beers courtesy of some happy financial planning in our favour. The evening started with Anna Simonin from the University of Sydney discussing Neurospora crassa, a filamentous fungus that forms extensive networks by fusion of the hyphae. Anna presented some amazing live imaging of the heady flow of cytoplasm between the fungal filaments. This clever architecture is thought to influence how nutrients are distributed around the colony. To explore how these streams of nutrient traffic may be contributing to Neurospora’s substrate utilisation, the movement of stable isotope labelled amino acids was tracked within a mutant unable to fuse filaments, a mutant that had lowered fusion ability and the wild type.
 

Event Date: 
Wednesday, March 28, 2012 - 18:15 - 18:30
Institution: 
Macquarie University
Title: 

Making and breaking dimethylsulfide in salt marsh sediments

Abstract: 

DMSP (dimethylsulfoniopropionate) is a key organic compound in the sulfur cycle with ~10^9 tons of this anti-stress compatible solute being made each year by marine phytoplankton, macro-algae and some salt marsh plants. The DMSP that is liberated is catabolised in a series of different microbial reactions that comprise a massive set of biotransformations in the global sulfur cycle. Some of the reaction products, such as DMS (dimethylsulfide), have major environmental consequences in their own right, from climate regulation to animal behaviour. Our work investigates microbial populations that cycle DMSP and DMS in coastal intertidal sediments. Combining geochemical and molecular biological approaches, such as stable isotope probing (SIP) and targeted high throughput sequencing, we are identifying the main microbial players that catabolise DMSP and DMS in oxic and anoxic parts of intertidal sediments alongside the key genes and cognate biochemical pathways that contribute to the turnover of these influential molecules. Early work led to the observation of a vertical microbial population structure within the salt marsh sediment, partially linked to the sulfur cycle biochemistry of this ecosystem. SIP experiments are allowing the characterisation of active microbial processing of DMSP and DMS compounds by separate new bacterial groups, closely associated to salt marsh plants and within the oxic sediment layer. This work is filling in major gaps in our knowledge of the global organic S cycle and the role of microbial populations in major environmental biochemical processes.

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