Oct 7 2004
In a world first, Australian scientists have successfully grown an unusual square-shaped bacterium found in salt lakes that has mystified scientists for a quarter of a century.
The research by PhD student Mr David Burns, Dr Mike Dyall-Smith and others at the University of Melbourne’s Department of Microbiology and Immunology opens the door to a huge field of exploration of major ecological significance to Australia, greatly expanding the known microscopic biodiversity of salt lakes.
The research team recently published a report (FEMS Microbiology Letters) on the first successful cultivation of ‘Walsby’s square bacteria’ (named after the British microbiologist who discovered them), something that scientists had failed to achieve since they were first discovered in 1980.
The bacteria are the most numerous type of cell found in salt lakes and are believed to be responsible for their characteristic red colour (for example, ‘Pink Lakes’ in the Murray-Sunset National Park, Victoria). Unusually, they are perfectly square in shape, appearing like small tiles when viewed under the microscope.
Dr Dyall-Smith says “they form such a large proportion of micro-organisms in salt lakes, their metabolic activities must be of major ecological significance as they do most of the conversion of organic nutrients to other compounds, including greenhouse gases.”
In order to study them properly it was necessary to grow them in the lab, but since their discovery 25 years ago, nobody had been able to achieve this.
“This was a major embarrassment to environmental microbiologists,” he says. “The most common microbe in salt lakes, and one of the most strangely shaped microbes ever discovered, could not be grown in the lab. Other bacteria in salt lakes could be grown, but not the squares.”
Dr Dyall-Smith and colleagues, despite losing ARC funding, recently published the first description of how these square organisms can be cultivated in the laboratory, providing the first definitive proof that they are cells just like other bacteria. Dr Dyall-Smith says the bacteria are ‘extremophiles’ meaning they have adapted to grow in saturating salt, and belong to the third major lineage of cells, the Archaea.
“We are now at a very exciting time where we can study the idiosyncrasies of these organisms, such as why they have been so difficult to culture, why they are so successful in their natural environment and how they interact with other organisms.
“Why are they square? We don’t know, but at least now we are on our way to finding out.”