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Issue 467, 21 May 2001

Coating of ‘sugar’ helps the silica go down

Tiny bacteria which manage to survive the intense temperatures and hostile environment of hot volcanic springs, may help us to understand the formation of rock deposits containing some of the earliest records of life on Earth.

Dr Liane G Benning, of Earth Sciences, has received a Leverhulme Trust grant of £93,390 over 3 years, to research the formation of silica which build up into rock formations surrounding hot springs. Laboratory experiments attempting to duplicate hot spring environments have produced similar deposits, but they form tens to hundreds of times slower than those found in nature.

Silica rocks – Dr Liane G Benning with examples of deposits taken from hot springs in the Taupo volcanic region of New Zealand

It is believed that this difference may be due to the activity of microbes, mostly cyanobacteria, which are protected from the chemical and environmental conditions in the springs by a sheath made up of various sugar components, or polysaccharides. The silica appears to form on these sheaths, but the precise role of the microbes and their ‘sugar coating’ in starting and enhancing silicification has not been determined.

Using a flow-through system at temperatures between 25 and 600C to simulate a hot spring environment, Dr Benning and colleague Dr Kurt Konhauser will mimic the process in the laboratory, allowing them to study the mechanisms and processes of silica formation in relation to the cyanobacteria.

"The research has a variety of applications," said Dr Benning. "In many countries, the heat from hot springs is used as an energy source, but deposits of silica can often cause problems by blocking pipes and conduits.

The silicification process is also linked to the formation of ore deposits, which provide important economic resources. In addition, understanding at a detailed level how modern silica forms will help us to understand how ancient siliceous rocks were formed, such as Precambrian stromalites. These ancient silica deposits preserve some of the earliest records of life on Earth."

For further information, see the leverhulme website

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