Wildlife is on the rocks

There is a generally accepted hypothesis that the majority of the biomass on the planet is underground rather than being found as plant and animal production on the surface or in the oceans. The majority of this biomass comprises fungi, bacteria, viruses and prions, together with algae and cyanobacteria in the oceans and lakes. We learn, in the excellent Introduction to Geomicrobiology by Kurt Konhauser, that these include organisms found in deep mines, in the interstices of rocks and those living in extraordinarily stressed conditions such as heat, acidity or alkalinity - extremophiles in areas such as hot springs or deep sea volcanic vents.

These micro-organisms are responsible for a wide range of processes such as the recycling of nutrients and the concentration and deposition of heavy and precious metals or minerals. They are also responsible for much of the methane production generated in organic mud deposits from marine and freshwater environments.

The first two chapters are concerned with the basic properties of all micro-organisms - diversity and metabolism. Full details are given and mechanisms are well explained, and these chapters would grace any good introductory text on microbiology.

The next chapter deals with microbial surface reactions and their relationship with metal and other chemical species. The chemistry and biology of these reactions are complex and may be either passive or active processes, and they are highly modified by the chemical environment in which they are found - aerobic or anaerobic, acid or basic. A by-product of this microbial search for energy, nutrient and inhabitable surfaces is the degradation of surfaces, the mineralisation and concentration of many environmentally important materials, including magnetites, phosphates, silica and species involved with fossilisation of animal and plant species.

Another aspect of this microbial ecology is seen in weathering processes of mineral surfaces, in particular of silicates and carbonates, by etching surfaces, sensitising them to gross weathering processes or making them available for fungal and other microbial invasion.

The penultimate chapter considers microbial zonation such as photosynthetic or chemical mat development. This is examined in detail in relation to marine sediments that represent the major ecosystem of the world and is one of the significant global carbon traps.

Finally, Konhauser examines the evolution of microbial organisms and their place in modifying the atmospheric structure of the planet and the evolution of other life forms. He manages successfully to bridge the gap between microbiology and palaeontology.

The text is well illustrated with clear, informative and well-described diagrams and some splendid electron micrographs with convincing evidence for mineral deposition by bacterial action. A good index and up-to-date references make this a book that undergraduates of any biological discipline could use as an introductory text that would be useful throughout their course. It would not hurt a few more experienced biologists either.

Tony Andrew is lecturer in environmental science and biology, Ulster University.