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Cardiff surface scientists to be “SLiMEd”.

27 July 2010

Prof Mike Bowker & Dr Phil Davies are part of a team spearheaded by Prof Parkes (Head of Cardiff University’s Earth and Ocean Sciences) that have been awarded a grant of £650k to investigate the generation of hydrogen by microorganisms that are present under the Earth’s surface at depths of up to ~3 km. This Subsurface LithoAutotrophic Microbial Ecosystem (SLiME) was discovered in basalt formations in 1995 and it has been estimated that the majority of prokaryotes on Earth may actually reside in the subsurface despite the high temperatures and pressure conditions found there. This may have implications for the origin of life on Earth and even the presence of life on planets such as Mars. 

However, the energy source that allows the subsurface microorganisms to be independent of photosynthesis remains very controversial. An early suggestion was that the organisms make use of hydrogen formed from the interaction of water with freshly cleaved iron containing rocks. But is enough hydrogen generated by this means? Critics have pointed out that the alkaline conditions, the limited availability of suitable iron containing rocks and of fresh reactive surfaces would result in less hydrogen than is needed. 

However, recent work by Parkes et al. has suggested that some prokaryotes actually speed-up hydrogen formation from minerals in sediment slurries, including hydrogen generation from pure silica sand. As silicates make up ~95% of the Earth's crust this could potentially be a very significant source of hydrogen. The team will investigate this possibility using a range of minerals and samples of prokaryotes extracted from the subsurface region. The Surface science team will explore the mechanism of the hydrogen generation and the sensitivity to particular mineral faces.

Scanning tunnelling microscopy image of an iron oxide surface recorded 
in the Surface Science laboratory at Cardiff with the inset showing 
atomic resolution of part of the terrace.