Saturday, 23 February 2013

Life in the Dark

In caves deep beaneath the Nullarbor Plain (a desert region in Australia which is actually the world's single largest piece of limestone, more than a thousand miles across) live strange slimy microbial communities known as microbial "slime curtains". A very poetic name, I think. These organisms live in the dark in ancient salty water, with little or no input of fresh water or organic nutrients from the surface.

In tune with the the title of this blog, we were curious about the lifestyle of these bugs- how do they make a living in such a unusual setting? We've just published a paper entitled- "Life in the Dark: metagenomic evidence that a microbial slime community is driven by inorganic nitrogen metabolism" in the ISME Journal which tries to answer this question.

We received samples of the slime curtains from cave divers exploring Weebubbie Cave, and we broke those cells open, collected the DNA from the whole community, and then sequenced that DNA (this is known as metagenomic sequencing). Computational analyses of the millions of genes detected were used to see what we could learn about these bugs. What we found was that the microbial cave slimes consist of about 1000 different microorganisms, but one particular bug made up almost half of the total community. This dominant bug was a Thaumarcheota (yes I know that just rolls off the tongue) and almost certainly gets its energy by oxidizing ammonia found in the cave water. So, we think that ammonia oxidation is what enables this community to flourish within the caves.

Scanning electron micrograph of the microbial cave slimes, the long filaments we think are the Thaumarcheota

Cave divers (photo courtesy of Liz Rogers)

Microbial cave slimes in Weebubbie cave (photo courtesy of Peter Rogers)

Cave diver taking a sample of cave slimes for our lab to investigate (photo courtesy of Steve Trewavas)

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