University researcher contributes to study into the limits of life on Earth

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University researcher contributes to study into the limits of life on Earth

Dr Hayley Manners and colleagues found single-celled microorganisms living in sediments more than a kilometre into the ocean floor

Dr Hayley Manners with a colleague on board the drillship Chikyu

Mr Alan Williams

Media and Communications Manager

Corporate Communications (Marketing and Communications)

31 March 2021

A ��Ʒ��Բ� researcher is part of an international team that has provided new insights into the temperature limits of life beneath the ocean floor.

Dr Hayley Manners, Lecturer in Organic Chemistry, and colleagues from 29 different institutes found single-celled microorganisms living in sediments more than a kilometre into the ocean floor – and at a temperature of 120°C.

The study, published in , was carried out during a two-month research expedition in 2016 – in which Dr Manners participated – and forms a part of the work of Expedition 370 of the International Ocean Discovery Program (IODP).

It focused on the Nankai Trough off the coast of Japan, where the deep-sea scientific vessel Chikyu drilled a hole 1,180 meters deep to reach sediment at 120°C.

In detailed analyses of the samples, scientists found the concentration of vegetative cells decreased sharply to a level of less than 100 cells per cubic centimetre of sediment at over 50°C.

However, the concentration of endospores – dormant cells of certain types of bacteria that can reactivate and switch to a live state whenever conditions are favourable again – increases rapidly and reaches a peak at 85°C.

The research was led by scientists at MARUM, the Centre for Marine and Environmental Sciences at the University of Bremen in Germany.

Dr Manners became involved as a result of previous work to investigate the role of volcanism in the marine carbon cycle. That work led to the discovery of novel chemical signatures in volcanic products buried in the deep biosphere, which it was believed could be signatures of distinct microbial life living in the volcanic layers. The IODP Expedition enabled her to expand on that as it focused on microbial life in extreme environments, in a region of the world known to be volcanically active. She said:

“The study has highlighted just how extreme an environment life can survive in – these are places which are not particularly abundant in the sources of energy which life requires to thrive. Couple this with the extreme temperatures (up to 120°C) and it makes a pretty amazing discovery, raising questions on the extent of life not only on this planet, but extra terrestrially too.”

Dr Hayley Manners on board the drillship Chikyu

Like the search for life in outer space, determining the limits of life on the Earth is fraught with great technological challenges. Temperatures of 120°C are normally encountered at about 4,000 meters below the sea floor, and using the Chikyu is the only way in the world for scientists to obtain samples from such great depths.

The sampling site used in this study lies in a water depth of 4.8km, but because of the steeper-than-average geothermal gradient, it was possible to reach a temperature of 120°C in a hole only 1,180 meters deep. The processing of samples was monitored using strict contamination controls, and for particularly critical work the samples were transported by helicopter to the cleanroom laboratories at the IODP core repository in Kochi, Japan.

Study leader Kai‐Uwe Hinrichs, of MARUM, said:

“Only a few scientific drilling sites have yet reached depths where temperatures in the sediments are greater than 30°C. The goal of the T-Limit Expedition, therefore, was to drill a thousand-meter deep hole into sediments with a temperature of up to 120°C – and we succeeded.”

Dr Hayley Manners with colleagues on board the drillship Chikyu

Dr Hayley Manners
with a colleague on board the research vessel Chikyū, investigating life in the
deep biosphere

The full study - Heuer et al: Temperature limits to deep subseafloor life in the Nankai Trough subduction zone - is published in Science, doi: .

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