title: Membrane homeoviscous adaptation in the piezo-hyperthermophilic archaeon Thermococcus barophilus.
abstract: The archaeon Thermococcus barophilus, one of the most extreme members of hyperthermophilic piezophiles known thus far, is able to grow at temperatures up to 103°C and pressures up to 80 MPa. We analyzed the membrane lipids of T. barophilus by high performance liquid chromatography-mass spectrometry as a function of pressure and temperature. In contrast to previous reports, we show that under optimal growth conditions (40 MPa, 85°C) the membrane spanning tetraether lipid GDGT-0 (sometimes called caldarchaeol) is a major membrane lipid of T. barophilus together with archaeol. Increasing pressure and decreasing temperature lead to an increase of the proportion of archaeol. Reversely, a higher proportion of GDGT-0 is observed under low pressure and high temperature conditions. Noticeably, pressure and temperature fluctuations also impact the level of unsaturation of apolar lipids having an irregular polyisoprenoid carbon skeleton (unsaturated lycopane derivatives), suggesting a structural role for these neutral lipids in the membrane of T. barophilus. Whether these apolar lipids insert in the membrane or not remains to be addressed. However, our results raise questions about the structure of the membrane in this archaeon and other Archaea harboring a mixture of di- and tetraether lipids.
authors.affiliation: CNRS, Laboratoire de Géologie de Lyon, Ecole Normale Supérieure de Lyon, UMR 5276, Université Claude Bernard Lyon 1 Lyon, France.
authors.forename: Anaïs
authors.initials: A
authors.lastname: Cario
authors.affiliation: CNRS, Laboratoire de Géologie de Lyon, Ecole Normale Supérieure de Lyon, UMR 5276, Université Claude Bernard Lyon 1 Lyon, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Grossi
authors.affiliation: CNRS, Laboratoire de Biogéochimie Moléculaire, Institut de Chimie de Strasbourg, Ecole de Chimie, Polymères et Matériaux, UMR 7177, Université de Strasbourg Strasbourg, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Schaeffer
authors.affiliation: CNRS, Laboratoire de Géologie de Lyon, Ecole Normale Supérieure de Lyon, UMR 5276, Université Claude Bernard Lyon 1 Lyon, France.
authors.forename: Philippe M
authors.initials: PM
authors.lastname: Oger
keywords: GDGT-0; Thermococcus barophilus; archaeal lipids; archaeal membrane; archaeol; deep-biosphere; homeoviscous adaptation; piezophily