Secretive bacteria provide clues to limits of life

A Charles Darwin University researcher is working to uncover a community of secretive microscopic organisms living under crystals in one of Australia’s most extreme micro-environments.

Near the small township of Kalkarindji (formerly Wave Hill) located 780km south of Darwin in the Northern Territory, among the arid sands and tufts of spinifex lies a phenomenon that is exciting NASA scientists because of its similarities to life that could have existed on Mars.

The area is abundant in quartz and agate crystals, but it is what lies beneath those crystals that has Professor Keith Christian intrigued.

“These unusual organisms have attracted attention in recent years because they are thought to be similar to the early terrestrial life on Earth and possibly similar to any life that may have existed on Mars,” Professor Christian said.

Called hypolithic cyanobateria, these organisms use the light passing through translucent rocks to photosynthesise and grow. Professor Christian has been working with a team of researchers to study the vast area 30km south-east of Kalkarindji for several years.  

“This is a primitive bacteria that can live in extreme environments,” he said. “They can survive with very little moisture in temperatures of up to 70 C. However, much of the time, when it is too hot, too dry, or there is not the appropriate amount of sunlight passing through the rocks, the cyanobacteria are in a dormant state. They are only actively growing for about 900 hours a year, when conditions are favourable.”

A zoologist for more than 40 years, Professor Christian became interested in the microbiological phenomenon while pursuing a hobby with his son at Kalkarindji. 

“We were collecting rocks to polish and noticed that the translucent or milky rocks had a green slimy covering growing underneath, while the opaque rocks did not,” he said. “When we returned to Darwin, we investigated further to find out why. We discovered that it was not only a unique group of primitive bacteria, but that research was being conducted on hypolithic cyanobateria in deserts around the world.” 

Working with a team of zoologists and microbiologists from Charles Darwin University and the Australian Institute of Marine Science to conduct DNA analysis, Professor Christian discovered that up to 22 species of cyanobacteria co-existed on one rock. All up the team found 60 different species after surveying rocks along a 10km portion of the expanse. 

“We discovered that the bacteria found at our site in Australia were unlike the cyanobacteria species found in deserts of North and South America. Our site also had a higher species diversity than those living in drier deserts.”

He said the reason NASA was so interested was because these microscopic organisms could provide clues to the limitations of life.

“There is more to know about the characteristics of these organisms and their ability to live in areas of extreme temperatures, with limited moisture and light. These organisms push the boundaries of what is possible.”

Professor Christian said the next step would be to further understand the bacteria’s diversity and dispersal.

The team lead by Professor Christian includes CDU researchers Professor Karen Gibb, Dr Chris Tracy, Dr Mirjam Kaestli, and Dr Claire Streten from the Australian Institute of Marine Science.


Source: CDU enews 
Issue 11 - 7 December 2015