Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338
May 23, 2001
Research answers mysteries of life 'underground'
For the first time, researchers -- including a University of Guelph microbiologist – have a direct measurement of how life manages to survive miles beneath the Earth’s surface without complex food and air.
The research published in the May 18 issue of Science magazine focuses on the microscopic bacterium Shewanella, which can thrive in an environment devoid of oxygen. The study showed that the bacterium actually adheres to iron oxide minerals in order to feed on iron, trapping electrons for metabolic energy. “This bacterium is literally eating minerals to stay alive, it is quite remarkable. It is amazing that life exists down there at all,” said Terry Beveridge, a professor in Guelph’s Department of Microbiology, who conducted the study with Steven Lower and Michael Hochella of Virginia Polytechnic Institute and State University. The bacterium even recognizes its preferred food source, producing special proteins on its surface when it makes contact with iron-containing minerals. In turn, these proteins “grip” the iron source with incredible force, allowing the bacterium to have its fill. “This type of recognition between a micro-organism and a mineral surface has been suggested but never quantified,” Beveridge said.
The strength of the bacterium’s “protein grip” was measured using a specially designed biological force microscopy technique that quantifies force at the nanoscale level. This technique was vital because the bacterium is so tiny, hundreds of thousands of them can fit on the tip of a needle. The scientists say their study revealed little-known information about the relationship between the bacterium and iron-containing minerals. This includes the fact that Shewanella produces the proteins for adhesion in an environment where oxygen is very limited. “That makes sense, given that this beast lives way under the ground where there is no air available,” Beveridge said. “These bacteria can be so deep within the Earth’s surface that it would take 50,000 years for rainwater to get down to them. There is no light, no photosynthesis and no complex sugars or proteins to feed on. It means this is a very primitive, but very resilient, form of life.”
Beveridge added that since bacteria both wear-down and even develop new minerals, some of the Earth’s surface is actually made up of the bacterium’s “left overs.” “It’s hard to believe that these simple life forms so altered geology,” he said. “Our estimates suggest that a mass equal to that of the Earth’s exposed crust has been reworked by microbial life over the more than three billion years of life’s existence. Geologists have to stand back and take another look at the impact of biology on the minerals they study.”
The scientists said their study not only provides an improved fundamental understanding of how bacteria interact with solid surfaces, but it also advances the use of “nanotechnology” to quantify and characterize those interactions. “This bacterium could be representative of many bacteria down there,” Beveridge said. “Strangely, an examination like this one at the molecular level actually helps us understand things on the huge global level.”
For media questions, contact: Communications and Public Affairs, 519-824-4120, Ext. 3338.