Science - December 14, 2010

First publication prize goes to worm study

Worms increase the production of laughing gas in the soil. MSc student Lucas Nebert discovered how, and won Wageningen’s first Publication Prize.

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Worms stimulate the emission of laughing gas (N 2 O) into the atmosphere. This much has been known for some time. But exactly how they achieve this was not clear until now. Because worms do not produce laughing gas themselves. MSc student of Soil Science Lucas Nebert has convincingly solved the riddle, for which he received the first Wageningen Publication Prize last week. Virtually, at least: Nebert has already returned to the US, where he comes from. But his supervisor Jan Willems van Groenigen explains the significance of Nerbert's work.

Maize
Nebert looked at what happened to the remains of maize plants in soils with different species of worms. To do this he used plant remains labeled with 15 N, an isotope of nitrogen. He drew his conclusions on the basis of the distribution of this isotope in the soil, the laughing gas that was released, the worms themselves and the microbial life in the soil. It was quite clear that the worms stimulate the micro-organisms to produce more laughing gas. Nebert showed an increased activity of denitrifying enzymes which convert nitrate and nitrite into laughing gas and nitrogen.

Slime
This effect of worms on the microbial activity has now been incontrovertibly demonstrated, Van Groenigen explains. 'And that takes us one step nearer to clarifying the mechanism underlying emissions of laughing gas from the soil.' The impact of worms on laughing gas production comes about through substances in the slime tracks they leave behind them, according to Van Groenigen. Those substances influence the enzyme production of bacteria. There is also a soil physics-related effect. Worms change the soil structure locally and worm corridors can function as little 'chimneys' which make the exchange of gases easier.

Winner
The Publication Prize of the Wageningen University Fund is being awarded for the first time this year. The prize is intended for a student who graduates with an article or a thesis based on an article. Nebert's paper has been submitted to the journal Applied and Environmental Microbiology. The prize was well-deserved, says Van Groenigen. 'He is a very clever and highly motivated lad. It was mainly his doing that the microbial analysis was introduced into our lab. And besides, he writes well and has a very mature attitude to science. He is an exceptionally good student.'

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