The discovery of an unusual micro-organism in the ocean may force scientists to rethink their understanding of how carbon and nitrogen cycle through ocean ecosystems.
A team of researchers at the University of California characterised a novel species of cyanobacteria by sequencing the metagenome of an ocean sample with the GS FLX Titanium series reagents from 454 Life Sciences.
The study details the discovery of what is believed to be a new form of cyanobacteria, a group of photosynthetic bacteria formerly known as blue-green algae.
Unlike all other known free-living cyanobacteria, this species lacks the genes needed for carbon fixation and photosynthesis, the light energy-dependent process that converts carbon dioxide and water into sugars, the by-product of which is oxygen.
The microbe also provides natural fertiliser to the oceans by fixing nitrogen from the atmosphere into a form usable by other organisms.
Lead researcher Jonathan Zehr said: 'We're trying to understand how something like this can live and grow with so many missing parts.' Earlier research by Zehr's group had revealed surprisingly large numbers of nitrogen-fixing cyanobacteria in coastal waters and the ocean.
Although 80 per cent of the Earth's atmosphere is nitrogen gas, most organisms cannot use it unless it is fixed to make molecules such as ammonia and nitrate.
Because nitrogen is essential for all forms of life, nitrogen fixation is a major factor controlling biological productivity in the oceans.
Zehr added: 'The new microbe is one of the most abundant nitrogen fixers in many parts of the ocean.
'Ecologically, it's important to understand its role in the ecosystem and how it affects the balance of carbon and nitrogen.' The new cyanobacteria was characterised by rapid high-throughput sequencing of genomic DNA from an enriched ocean water sample using the GS FLX Titanium series reagents.
The study is the first paper published using the upgraded chemistry series, which generates more than one million individual reads per run, with read lengths greater than 400 base pairs.
Zehr added: 'We have been trying unsuccessfully to culture this organism for years and with data from a single GS FLX Titanium run, produced in days, we were able to obtain valuable genomic information directly from an environmental sample.' The team hopes to continue its research by mapping the microbe's presence in the oceans.
The team also aims to discover how the organism's metabolism differs from other cyanobacteria.
While this bacteria has not yet been cultured, the new genomic information opens potential avenues to exploit its unusual metabolism in biotechnology applications.
The study, titled 'Globally Distributed Uncultivated Oceanic N2 - Fixing Cyanobacteria Lack Oxygenic Photosystem II' appears in the 14 November issue of Science.
