- Fungus from a deep-sea sediment core that is hundreds
of thousands of years old can grow when placed in culture, scientists have
discovered.
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- Indian researchers say the fungi come from sediments
that are between 180,000 and 430,000 years old.
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- The finding adds to growing evidence for the impressive
survival capabilities of many microorganisms.
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- They are the oldest known fungi that will grow on a nutrient
medium, the scientists say in Deep Sea Research I.
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- The core was drilled from a depth of 5,904m in the Indian
Ocean's Chagos Trench.
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- Like other ocean trenches, it is oriented parallel to
a volcanic arc and is one of the deepest regions of the Indian Ocean.
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- On board their research vessel, Dr Chandralata Raghukumar
and colleagues from the National Institute of Oceanography in Goa, India,
and the Indian Institute of Chemical Technology in Hyderabad carefully
deposited 5cm-long portions of the core into plastic bags which they then
sealed to avoid contamination with present-day microbes.
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- The scientists then attempted to isolate bacteria and
fungi from the middle of the 5cm-long "subsamples", because this
region had not been in contact with the pipe used to extract the core -
and therefore any modern microorganisms on it.
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- Blown away
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- Diluted malt extract agar was used as a nutrient medium
to grow the fungus on. The team was able to culture fungi from six out
of 22 subsections of the core.
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- At core depths of between 15 and 50cm, the scientists
found fungus of a type that does not produce spores.
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- At a depth of 160cm (corresponding to an age of 180,000
years ago) they found high densities of a type of spore-producing fungus
known as Aspergillus sydowii .
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- Considerable densities of this fungus were also found
at depths of 280-370cm, corresponding to an age between 180,000 and 430,000
years ago.
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- The researchers think the microbes may be blown off the
land into the sea. They then sink to the sea floor and are covered in deep-sea
ocean sediments.
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- The oldest microorganisms found alive are thought to
be bacteria isolated from 25-40-million-year-old bees trapped in amber.
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- In 2000, US researchers claimed to have found bacteria
that had remained in suspended animation for 250 million years in salt
crystals. But the claim was disputed almost as soon as it was made.
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- Microbiologist Dr Scott Rogers, of Bowling Green State
University in Ohio, US, was unsurprised by the study, saying his own team
had obtained similar dates for ancient fungal organisms they had recovered
in ice.
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- Viable and perhaps actively growing microorganisms are
also thought to survive in the depths of Lake Vostok in Antarctica. If
so, they may have been isolated from outside communities of microorganisms
for up to one million years.
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- Studying the distributions and numbers of fungal organisms
in cores could tell scientists about past climatic conditions on Earth,
say the authors of the study.
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- © BBC MMIV http://news.bbc.co.uk/2/hi/science/nature/3754090.stm
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