6 September
2006 - Scientists at the Danish National Environmental
Research Institute (NERI) and the University of
Aarhus are in front of an international research
team that is presenting ground-breaking news this
week in the renowned journal Nature. These researchers
have found small animals on the sea floor that
breathe nitrate instead of oxygen. This means
the textbooks will have to be rewritten – as regards
both the nitrogen cycle and the ability of animals
to survive without oxygen.
Life without oxygen
Foraminifera are single-celled
animals (protozoa) surrounded by a shell of varying
size and form. They are found in vast numbers
on sea beds all over the world. The scientists
have now discovered that some foraminifera can
breathe nitrate when they inhabit environments
with no oxygen.
Foraminifera can gather an enormous
stock of nitrate close to the surface of the sea
floor. Filled up with nitrate, these organisms
can live deeper down in the sea bed, where there
is plenty of food and there are very few predators.
In this oxygen-free environment, they breathe
nitrate and can thus – in a manner of speaking
– hold their breath for weeks.
How higher-ranking organisms
like foraminifera have become capable of breathing
nitrate remains a mystery. The solution will have
to await the numerous investigations that will
now be put in motion on the basis of this new
discovery.
New understanding of the nitrogen
cycle
The research team – led by Nils
Risgaard-Petersen from NERI – has demonstrated
that foraminifera breathe the same way known for
years from bacteria, which remove nitrate-nitrogen
by the process of denitrification. These bacteria
are actively used in wastewater treatment plants
and wetlands to reduce the nitrate pollution stemming
from urbanisation and land cultivation.
This means the process itself
is not new. However, the fact that animals can
breathe nitrate is a ground-breaking discovery,
which immediately raises new questions. How many
animals can breathe and live the same way? Are
they important enough that our understanding of
the global nitrogen balance needs to be revised?
Just five years ago, Danish
scientists from institutions including NERI revealed
that a totally unheeded bacterial process called
anammox also removes large amounts of nitrogen
from the environment. What we learned at school
about how nitrogen circles the earth is being
put to the test at present, and scientists are
convinced that new discoveries are just round
the corner.
Searching for oil
Geologists belong to the group of people who are
particularly interested in the new discovery.
Foraminifera shells are actually important clues
that provide information about the environment
and climate changes that have taken place over
several hundred million years. The ancient shells
– the fossils – indicate places where it is worth
drilling for oil and other resources. And with
new knowledge about the lifestyle of the foraminifera,
geologists will be better able to decipher the
clues left by these organisms.
Continues on the GalatheaExpedition
On board the Galathea Expedition – which has just
sailed from Denmark to begin an 8 month scientific
expedition – the Danish scientists will continue
their hunt around the world for new animals and
bacteria that breathe nitrate.
Further information:
Senior Scientist Nils Risgaard-Petersen
Associate Professor Lars Peter Nielsen, University
of Aarhus
Risgaard-Petersen N, Alexandra M. Langezaal, Signe
Ingvardsen, Markus C. Schmid, Mike S. M. Jetten,
Huub J. M. Op den Camp, Jan W. M. Derksen, Elisa
Piña-Ochoa, Susanne P. Eriksson, Lars Peter
Nielsen, Niels Peter Revsbech, Tomas Cedhagen
& Gijsbert J. van der Zwaan (2006). Evidence
for complete denitrification in a benthic foraminifer.
