UNIVERSITY PARK, Pa. — The missing step in the formation of a lipid molecule that allows certain single-celled organisms to survive the most extreme environments on Earth has now been deciphered. This new understanding, uncovered by a team of biochemists from Penn State and the University of Illinois Urbana-Champaign, could improve the ability of the lipids to be used as an indicator of temperature across geological time.
The lipid, called glycerol dibiphytanyl glycerol tetraether (GDGT), is found in the cell membrane of some species of archaea, single-celled organisms that were originally thought to be bacteria but now are considered a separate group. This lipid provides the stability for some species to thrive in environments with extremely high temperatures, salinity or acidity, like thermal vents in the ocean, hot springs and hypersaline waters. The unique stability of GDGT also allows it to be detected hundreds or even thousands of years after the organism dies. Because these organisms tend to produce more GDGT at higher temperatures, it is considered a promising candidate for estimating temperature over geologic time.
“For GDGT to be accurately used as a proxy to reconstruct changes in geological temperatures, scientists need to better understand how it is made, what genes code for it, and which species can create it,” said Squire Booker, a biochemist at Penn State, an investigator with the Howard Hughes Medical Institute, and leader of the research team. “But, until now, there has been a missing step in the formation of this lipid. We used imaging techniques coupled with chemical and biochemical methods to deconstruct the chemical pathway for this missing step.”
GDGT’s stability is in part due to its two long hydrocarbon chains that extend throughout the membrane. But how these two chains become linked together has puzzled scientists for decades.