Cloning the smell of the seaside - molecular genetics of dimethyl sulphide production by bacteria

Project Details


We've all been to the seaside and we've all been told by a knowing parent to "breathe in that ozone", because it's "good for you". Well, firstly, it's not ozone and second, it's not terribly good for you.
That distinctive aroma is, in fact another gas, called dimethyl sulphide (DMS) and it has been known since 1971 that it is hugely important, with some 30 million tons of it being liberated into the air, world wide, every year. And once in the atmosphere it has other major effects, being the "seed" that sets off cloud formation over the oceans. Indeed, it has been proposed that the production of this molecule is on such a scale that it has major effects on the world's climate.
Yet, despite all this, we have absolutely no idea of how, at a molecular level, this process occurs. This is all the more surprising since we have known for some time that many marine bacteria, some of which are easy to grow in the laboratory, can liberate DMS if supplied with the key precursor molecule, called Dimethylsulphiopropionate - DMSP for short. Not a compound one reads about every day, yet there are over two billion tonnes of it in the world's oceans, seas and seashores. That's the weight, give or take, of another seaside symbol, the Blackpool Tower - 70,000 times over. Amazing.
This DMSP molecule is used by the great masses of marine plant life - seaweeds and microscopic plankton - as a buffer, or osmo-protectant, against the saltiness of the sea. When these plants die, some of the DMSP that escapes from them is used as food by some marine bacteria and, when they do so, they convert some of it to the DMS gas in the process.
We recently isolated one such DMSP-consuming bacterium from the Norfolk coast and used various molecular techniques to get our hands on some of the genes that are involved. By looking at their sequences, we can guess what the genes might be doing and, so far, it looks as if the mechanisms are very different from those hypothetical ones that had been proposed before.
We also saw that very similar genes exist in some other, very unexpected, types of bacteria, such as those that live, symbiotically, on the roots of land plants. So the extent of DMS production by bacteria may be far wider and varied than we had thought.
We now hope to get a much deeper understanding on this process, at least in "our" strain. We want to identify and characterize all the enzymes that are involved and we want to know how the pathway is regulated - we already know that these bacteria are not stupid, since they only switch on their systems for degrading the DMSP if the compound is present in their environment. Once we know what is happening with this Norfolk strain, it should be fairly straightforward to find out if other types of marine bacteria that eat DMSP do so in the same way.
So, for the first time, we are close to getting a real insight into the molecular details of this pathway, allowing us to amuse, fascinate and educate our friends the next time we go to Great Yarmouth and somebody asks about the delicate scent of rotting seaweed that drifts up from the golden sands.
Effective start/end date31/08/0730/08/10


  • Biotechnology and Biological Sciences Research Council: £337,364.00