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Deirdre Gleeson has been exploring one of the frontiers of science, albeit a very tiny one: soil microorganisms.

The findings of the research, by Associate Professor Gleeson and her colleagues in the School of Earth and Environment, have been presented in international journals and conferences, and involved three postgraduate and undergraduate students.

Their work is helping unravel two of the mysteries of soil microorganisms: How do soil organisms contribute to greenhouse gas emissions? And why is their biodiversity so extraordinarily high?

The ARC Discovery Project was the first to examine how, in semi-arid soil, water influences a group of soil microorganisms that help regulate the Earth's climate. These microorganisms help to do this by producing the greenhouse gas nitrous oxide.

"Some of the findings were the opposite to what has been found in other regions of the world," Professor Gleeson said. "In semi-arid soils, different microorganisms dominated the community of ammonia oxidisers and they responded differently to water compared with other regions.

"These findings help us understand how nitrous oxide emissions from soil microorganisms may be affected by changing rainfall patterns. They may become relevant to other regions of the globe if climate changes cause them to become semi-arid."

Another first for the project was the testing of an emerging theory to explain why soil microorganisms are the most diverse group of organisms on Earth.

"One of the most intriguing puzzles in soil microbiology is how so many different bacterial species can coexist in small volumes of soil," said Professor Gleeson. "One promising theory has been tested in artificial soils but our research was the first to find evidence to support it using real soil."