title: Important roles for membrane lipids in haloarchaeal bioenergetics.
abstract: Recent advances in lipidomic analysis in combination with various physiological experiments set the stage for deciphering the structure-function of haloarchaeal membrane lipids. Here we focused primarily on changes in lipid composition of Haloferax volcanii, but also performed a comparative analysis with four other haloarchaeal species (Halobacterium salinarum, Halorubrum lacusprofundi, Halorubrum sodomense and Haloplanus natans) all representing distinctive cell morphologies and behaviors (i.e., rod shape vs. pleomorphic behavior). Common to all five haloarchaea, our data reveal an extraordinary high level of menaquinone, reaching up to 72% of the total lipids. This ubiquity suggests that menaquinones may function beyond their ordinary role as electron and proton transporter, acting simultaneously as ion permeability barriers and as powerful shield against oxidative stress. In addition, we aimed at understanding the role of cations interacting with the characteristic negatively charged surface of haloarchaeal membranes. We propose for instance that by bridging the negative charges of adjacent anionic phospholipids, Mg2+acts as surrogate for cardiolipin, a molecule that is known to control curvature stress of membranes. This study further provides a bioenergetic perspective as to how haloarchaea evolved following oxygenation of Earth's atmosphere. The success of the aerobic lifestyle of haloarchaea includes multiple membrane-based strategies that successfully balance the need for a robust bilayer structure with the need for high rates of electron transport - collectively representing the molecular basis to inhabit hypersaline water bodies around the planet.
authors: Department of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106, USA. Electronic address: kellermann.matthias@gmail.com.
authors: Matthias Y
authors: MY
authors: Kellermann
authors: MARUM Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, Leobener Strasse, D-28359 Bremen, Germany.
authors: Marcos Y
authors: MY
authors: Yoshinaga
authors: University of California, Davis, CA 95616, USA.
authors: Raymond C
authors: RC
authors: Valentine
authors: MARUM Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, Leobener Strasse, D-28359 Bremen, Germany.
authors: Lars
authors: L
authors: Wörmer
authors: Department of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106, USA. Electronic address: valentine@geol.ucsb.edu.
authors: David L
authors: DL
authors: Valentine
mesh_terms: D000222:Adaptation, Physiological; D000332:Aerobiosis; D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism; D005075:Biological Evolution; D002413:Cations, Divalent; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004579:Electron Transport; D004734:Energy Metabolism; D019617:Halobacterium salinarum / Q000737:chemistry / Q000378:metabolism*; D019622:Haloferax volcanii / Q000737:chemistry / Q000378:metabolism*; D055352:Halorubrum / Q000737:chemistry / Q000378:metabolism*; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010743:Phospholipids / Q000737:chemistry* / Q000378:metabolism; D054712:Salinity; D012623:Seawater / Q000737:chemistry / Q000382:microbiology; D055672:Static Electricity; D024482:Vitamin K 2 / Q000737:chemistry / Q000378:metabolism
chemical_list: D000975:Antioxidants; D002413:Cations, Divalent; D008563:Membrane Lipids; D010743:Phospholipids; D024482:Vitamin K 2; D008274:Magnesium; D010100:Oxygen
keywords: HPLC-MS; Lipidomic-bioenergetic analysis; Membrane adaptation; Membrane forming lipids, non-membrane forming lipids