25th International Meeting on Organic Geochemistry IMOG 2011

O-68
Latitudinal distribution of archaeal H-lipids
Carme Huguet 1 , Susanne Fietz 1 , Antoni Rosell-Melé 1,2
1 aInstitut de Ciència i Tecnlogia Ambientals, Universitat Autònoma de Barcelona, Cerdanyola, Spain,
2 cInstitució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain (corresponding
author:carme.huguet@uab.es)
The unique composition of Archaea‘s membrane
lipids allows them to maintain integrity and exchange
capabilities in moderate and extreme conditions 1 .
They adapt to a wide range of temperatures by
changing the number of rings in their glycerol dialkyl
glycerol tetraether (GDGT) membrane lipids, which is
used to estimate past water surface temperature via
the TEX86 index 2 . Here we report that mesophile
Archaea also synthesize an additional set of core
membrane lipids with a covalent bond between the
two chains (H- GDGTs) which were previously
thought to be restricted mainly to extremophiles 3 . We
propose that these lipids help mesophile Archaea to
adapt to cold conditions, maintaining their membrane
exchange capabilities. However, this contradicts
previous hypothesis that suggested H-GDGTs to be
an adaptation to withstand high temperatures. We
observe that H- GDGTs are widespread and
abundant in mesophilic marine and lacustrine
environments, and that surprisingly they increase in
abundance towards higher and colder latitudes (Fig.
1). The lowest H-GDGT abundances (0-23%) were
found between 0-45 ºN and 0-30 ºS strongly
increasing to 35-95% at 60-87ºN and 60-70ºS (Fig.
a b
1a). Moreover the contribution of H-GDGTs increases
as temperature decreases with values ranging from 0
at 25 ºC to 95% below 0 ºC. In fact the relative H-
GDGT abundance is significantly correlated with
temperature (R²= 0.64 p