Exoplanet Biosignatures: a Review of Remotely Detectable Signs of Life
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The Arctic Sea Ice Biomarker IP25: a Review of Current Understanding, Recommendations for Future Research and Applications in Palaeo Sea Ice Reconstructions
Quaternary Science Reviews 79 (2013) 9e25 Contents lists available at SciVerse ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev The Arctic sea ice biomarker IP25: a review of current understanding, recommendations for future research and applications in palaeo sea ice reconstructions Simon T. Belt a,*, Juliane Müller b a Biogeochemistry Research Centre, School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth PL4 8AA, UK b Alfred Wegener Institute for Polar and Marine Research, 27568 Bremerhaven, Germany article info abstract Article history: In recent years, a novel proxy for the past occurrence of Arctic sea ice has been proposed that is based Received 18 June 2012 on the variable marine sedimentary abundance of an organic geochemical lipid derived from sea ice Received in revised form diatoms in the spring. This lipid, termed IP25 (Ice Proxy with 25 carbon atoms), is a highly branched 29 November 2012 isoprenoid mono-unsaturated alkene that appears to be sufficiently stable in sediments to permit Accepted 4 December 2012 meaningful palaeo sea ice reconstructions to be carried out over short- to long-term timescales. Since Available online 17 January 2013 the first proposed use of IP25 as a proxy for palaeo sea ice by Belt et al. (2007), a number of laboratories have measured this biomarker in Arctic sediments and it is anticipated that research activity in this area Keywords: Sea ice will increase further in the future. The content of this review is divided into a number of sections. fi Arctic Firstly, we describe the scienti c basis for the IP25 proxy and its initial discovery in Arctic sea ice, Proxy sedimenting particles and sediments. -
The Discovery of Exoplanets
L'Univers, S´eminairePoincar´eXX (2015) 113 { 137 S´eminairePoincar´e New Worlds Ahead: The Discovery of Exoplanets Arnaud Cassan Universit´ePierre et Marie Curie Institut d'Astrophysique de Paris 98bis boulevard Arago 75014 Paris, France Abstract. Exoplanets are planets orbiting stars other than the Sun. In 1995, the discovery of the first exoplanet orbiting a solar-type star paved the way to an exoplanet detection rush, which revealed an astonishing diversity of possible worlds. These detections led us to completely renew planet formation and evolu- tion theories. Several detection techniques have revealed a wealth of surprising properties characterizing exoplanets that are not found in our own planetary system. After two decades of exoplanet search, these new worlds are found to be ubiquitous throughout the Milky Way. A positive sign that life has developed elsewhere than on Earth? 1 The Solar system paradigm: the end of certainties Looking at the Solar system, striking facts appear clearly: all seven planets orbit in the same plane (the ecliptic), all have almost circular orbits, the Sun rotation is perpendicular to this plane, and the direction of the Sun rotation is the same as the planets revolution around the Sun. These observations gave birth to the Solar nebula theory, which was proposed by Kant and Laplace more that two hundred years ago, but, although correct, it has been for decades the subject of many debates. In this theory, the Solar system was formed by the collapse of an approximately spheric giant interstellar cloud of gas and dust, which eventually flattened in the plane perpendicular to its initial rotation axis. -
Modeling Super-Earth Atmospheres in Preparation for Upcoming Extremely Large Telescopes
Modeling Super-Earth Atmospheres In Preparation for Upcoming Extremely Large Telescopes Maggie Thompson1 Jonathan Fortney1, Andy Skemer1, Tyler Robinson2, Theodora Karalidi1, Steph Sallum1 1University of California, Santa Cruz, CA; 2Northern Arizona University, Flagstaff, AZ ExoPAG 19 January 6, 2019 Seattle, Washington Image Credit: NASA Ames/JPL-Caltech/T. Pyle Roadmap Research Goals & Current Atmosphere Modeling Selecting Super-Earths for State of Super-Earth Tool (Past & Present) Follow-Up Observations Detection Preliminary Assessment of Future Observatories for Conclusions & Upcoming Instruments’ Super-Earths Future Work Capabilities for Super-Earths M. Thompson — ExoPAG 19 01/06/19 Research Goals • Extend previous modeling tool to simulate super-Earth planet atmospheres around M, K and G stars • Apply modified code to explore the parameter space of actual and synthetic super-Earths to select most suitable set of confirmed exoplanets for follow-up observations with JWST and next-generation ground-based telescopes • Inform the design of advanced instruments such as the Planetary Systems Imager (PSI), a proposed second-generation instrument for TMT/GMT M. Thompson — ExoPAG 19 01/06/19 Current State of Super-Earth Detections (1) Neptune Mass Range of Interest Earth Data from NASA Exoplanet Archive M. Thompson — ExoPAG 19 01/06/19 Current State of Super-Earth Detections (2) A Approximate Habitable Zone Host Star Spectral Type F G K M Data from NASA Exoplanet Archive M. Thompson — ExoPAG 19 01/06/19 Atmosphere Modeling Tool Evolution of Atmosphere Model • Solar System Planets & Moons ~ 1980’s (e.g., McKay et al. 1989) • Brown Dwarfs ~ 2000’s (e.g., Burrows et al. 2001) • Hot Jupiters & Other Giant Exoplanets ~ 2000’s (e.g., Fortney et al. -
Relevance of Phenotypic Information for the Taxonomy of Not-Yet-Cultured Microorganisms
Systematic and Applied Microbiology 42 (2019) 22–29 Contents lists available at ScienceDirect Systematic and Applied Microbiology j ournal homepage: www.elsevier.de/syapm Relevance of phenotypic information for the taxonomy of not-yet-cultured microorganisms a,b,c,∗ a a,b a a Jörg Overmann , Sixing Huang , Ulrich Nübel , Richard L. Hahnke , Brian J. Tindall a Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Inhoffenstraße 7B, 38124 Braunschweig, Germany b Deutsches Zentrum für Infektionsforschung (DZIF), Standort Braunschweig-Hannover, Braunschweig, Germany c German Center for Integrative Biodiversity Research (iDiv) Jena Halle Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany a r t i c l e i n f o a b s t r a c t Keywords: To date, far less than 1% of the estimated global species of Bacteria and Archaea have been described and Not-yet-cultured microorganisms their names validly published. Aside from these quantitative limitations, our understanding of phenotypic Taxonomy and functional diversity of prokaryotes is also highly biased as not a single species has been described Nomenclature for 85 of the 118 phyla that are currently recognized. Due to recent advances in sequencing technology Candidatus and capacity, metagenomic datasets accumulate at an increasing speed and new bacterial and archaeal International Code of Nomenclature of Prokaryotes genome sequences become available at a faster rate than newly described species. The growing gap between the diversity of Bacteria and Archaea held in pure culture and that detected by molecular methods has led to the proposal to establish a formal nomenclature for not-yet-cultured taxa primarily based on sequence information. -
Ices on Mercury: Chemistry of Volatiles in Permanently Cold Areas of Mercury’S North Polar Region
Icarus 281 (2017) 19–31 Contents lists available at ScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus Ices on Mercury: Chemistry of volatiles in permanently cold areas of Mercury’s north polar region ∗ M.L. Delitsky a, , D.A. Paige b, M.A. Siegler c, E.R. Harju b,f, D. Schriver b, R.E. Johnson d, P. Travnicek e a California Specialty Engineering, Pasadena, CA b Dept of Earth, Planetary and Space Sciences, University of California, Los Angeles, CA c Planetary Science Institute, Tucson, AZ d Dept of Engineering Physics, University of Virginia, Charlottesville, VA e Space Sciences Laboratory, University of California, Berkeley, CA f Pasadena City College, Pasadena, CA a r t i c l e i n f o a b s t r a c t Article history: Observations by the MESSENGER spacecraft during its flyby and orbital observations of Mercury in 2008– Received 3 January 2016 2015 indicated the presence of cold icy materials hiding in permanently-shadowed craters in Mercury’s Revised 29 July 2016 north polar region. These icy condensed volatiles are thought to be composed of water ice and frozen Accepted 2 August 2016 organics that can persist over long geologic timescales and evolve under the influence of the Mercury Available online 4 August 2016 space environment. Polar ices never see solar photons because at such high latitudes, sunlight cannot Keywords: reach over the crater rims. The craters maintain a permanently cold environment for the ices to persist. Mercury surface ices magnetospheres However, the magnetosphere will supply a beam of ions and electrons that can reach the frozen volatiles radiolysis and induce ice chemistry. -
Pinpointing the Origin of Mitochondria Zhang Wang Hanchuan, Hubei
Pinpointing the origin of mitochondria Zhang Wang Hanchuan, Hubei, China B.S., Wuhan University, 2009 A Dissertation presented to the Graduate Faculty of the University of Virginia in Candidacy for the Degree of Doctor of Philosophy Department of Biology University of Virginia August, 2014 ii Abstract The explosive growth of genomic data presents both opportunities and challenges for the study of evolutionary biology, ecology and diversity. Genome-scale phylogenetic analysis (known as phylogenomics) has demonstrated its power in resolving the evolutionary tree of life and deciphering various fascinating questions regarding the origin and evolution of earth’s contemporary organisms. One of the most fundamental events in the earth’s history of life regards the origin of mitochondria. Overwhelming evidence supports the endosymbiotic theory that mitochondria originated once from a free-living α-proteobacterium that was engulfed by its host probably 2 billion years ago. However, its exact position in the tree of life remains highly debated. In particular, systematic errors including sparse taxonomic sampling, high evolutionary rate and sequence composition bias have long plagued the mitochondrial phylogenetics. This dissertation employs an integrated phylogenomic approach toward pinpointing the origin of mitochondria. By strategically sequencing 18 phylogenetically novel α-proteobacterial genomes, using a set of “well-behaved” phylogenetic markers with lower evolutionary rates and less composition bias, and applying more realistic phylogenetic models that better account for the systematic errors, the presented phylogenomic study for the first time placed the mitochondria unequivocally within the Rickettsiales order of α- proteobacteria, as a sister clade to the Rickettsiaceae and Anaplasmataceae families, all subtended by the Holosporaceae family. -
Water, Habitability, and Detectability Steve Desch
Water, Habitability, and Detectability Steve Desch PI, “Exoplanetary Ecosystems” NExSS team School of Earth and Space Exploration, Arizona State University with Ariel Anbar, Tessa Fisher, Steven Glaser, Hilairy Hartnett, Stephen Kane, Susanne Neuer, Cayman Unterborn, Sara Walker, Misha Zolotov Astrobiology Science Strategy NAS Committee, Beckmann Center, Irvine, CA (remotely), January 17, 2018 How to look for life on (Earth-like) exoplanets: find oxygen in their atmospheres How Earth-like must an exoplanet be for this to work? Seager et al. (2013) How to look for life on (Earth-like) exoplanets: find oxygen in their atmospheres Oxygen on Earth overwhelmingly produced by photosynthesizing life, which taps Sun’s energy and yields large disequilibrium signature. Caveats: Earth had life for billions of years without O2 in its atmosphere. First photosynthesis to evolve on Earth was anoxygenic. Many ‘false positives’ recognized because O2 has abiotic sources, esp. photolysis (Luger & Barnes 2014; Harman et al. 2015; Meadows 2017). These caveats seem like exceptions to the ‘rule’ that ‘oxygen = life’. How non-Earth-like can an exoplanet be (especially with respect to water content) before oxygen is no longer a biosignature? Part 1: How much water can terrestrial planets form with? Part 2: Are Aqua Planets or Water Worlds habitable? Can we detect life on them? Part 3: How should we look for life on exoplanets? Part 1: How much water can terrestrial planets form with? Theory says: up to hundreds of oceans’ worth of water Trappist-1 system suggests hundreds of oceans, especially around M stars Many (most?) planets may be Aqua Planets or Water Worlds How much water can terrestrial planets form with? Earth- “snow line” Standard Sun distance models of distance accretion suggest abundant water. -
University Microfilms International T U T T L E , V Ir G in Ia G R a C E
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Additional Analysis of Cyanobacterial Polyamines Distributions Of
Microb. Resour. Syst. Dec.32(2 ):1792016 ─ 186, 2016 Vol. 32, No. 2 Additional analysis of cyanobacterial polyamines ─ Distributions of spermidine, homospermidine, spermine, and thermospermine within the phylum Cyanobacteria ─ Koei Hamana1)*, Takemitsu Furuchi2), Hidenori Hayashi1) and Masaru Niitsu2) 1)Faculty of Engineering, Maebashi Institute of Technology 460-1 Kamisadori-machi, Maebashi, Gunma 371-0816, Japan 2)Faculty of Pharmaceutical Sciences, Josai University, 1-1, Keyakidai, Sakado, Saitama 350-0295, Japan To further catalogue the distribution of cyanobacterial cellular polyamines, we used HPLC and HPGC to newly analyze the acid-extracted polyamines from 14 cyanobacteria. The colony-forming Nostoc verrucosum (“Ashitsuki”) and Nostoc commune (“Ishikurage”), as well as Anabaena species (Nostocales), contained homospermidine. The thermo-halotolerant Spirulina subsalsa var. salina (Spirulinales), as well as freshwater Spirulina strains, contained spermidine. Putrescine, spermidine, and homospermidine were found in freshwater colony-forming Aphanothece sacrum (“Suizenji-nori”), whereas the halotolerant Aphanothece halophytica and Microcystis species (Chroococcales) contained spermidine alone. In addition to putrescine, spermidine, homospermidine and agmatine, thermospermine was found as a major polyamine in haloalkaliphilic Arthrospira platensis (“Spirulina”) (Oscillatoriales). In the Synechococcales, chlorophyll b-containing Prochlorococcus marina contained spermidine, and chlorophyll d-containing Acaryochloris marina contained -
Two Unrelated 8-Vinyl Reductases Ensure Production of Mature Chlorophylls in Acaryochloris Marina
crossmark Downloaded from Two Unrelated 8-Vinyl Reductases Ensure Production of Mature Chlorophylls in Acaryochloris marina Guangyu E. Chen,a Andrew Hitchcock,a Philip J. Jackson,a,b Roy R. Chaudhuri,a Mark J. Dickman,b C. Neil Hunter,a Daniel P. Canniffea* a Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom ; ChELSI Institute, Department of Chemical and Biological http://jb.asm.org/ Engineering, University of Sheffield, Sheffield, United Kingdomb ABSTRACT The major photopigment of the cyanobacterium Acaryochloris marina is chlorophyll d, while its direct biosynthetic precursor, chlorophyll a, is also present in the cell. These pigments, along with the majority of chlorophylls utilized by oxygenic pho- totrophs, carry an ethyl group at the C-8 position of the molecule, having undergone reduction of a vinyl group during biosyn- thesis. Two unrelated classes of 8-vinyl reductase involved in the biosynthesis of chlorophylls are known to exist, BciA and BciB. The genome of Acaryochloris marina contains open reading frames (ORFs) encoding proteins displaying high sequence similar- on April 20, 2016 by PERIODICALS OFFICE, MAIN LIBRARY, UNIVERSITY OF SHEFFIELD ity to BciA or BciB, although they are annotated as genes involved in transcriptional control (nmrA) and methanogenesis (frhB), respectively. These genes were introduced into an 8-vinyl chlorophyll a-producing ⌬bciB strain of Synechocystis sp. strain PCC 6803, and both were shown to restore synthesis of the pigment with an ethyl group at C-8, demonstrating their activities as 8-vi- nyl reductases. We propose that nmrA and frhB be reassigned as bciA and bciB, respectively; transcript and proteomic analysis of Acaryochloris marina reveal that both bciA and bciB are expressed and their encoded proteins are present in the cell, possibly in order to ensure that all synthesized chlorophyll pigment carries an ethyl group at C-8. -
Biosignatures Search in Habitable Planets
galaxies Review Biosignatures Search in Habitable Planets Riccardo Claudi 1,* and Eleonora Alei 1,2 1 INAF-Astronomical Observatory of Padova, Vicolo Osservatorio, 5, 35122 Padova, Italy 2 Physics and Astronomy Department, Padova University, 35131 Padova, Italy * Correspondence: [email protected] Received: 2 August 2019; Accepted: 25 September 2019; Published: 29 September 2019 Abstract: The search for life has had a new enthusiastic restart in the last two decades thanks to the large number of new worlds discovered. The about 4100 exoplanets found so far, show a large diversity of planets, from hot giants to rocky planets orbiting small and cold stars. Most of them are very different from those of the Solar System and one of the striking case is that of the super-Earths, rocky planets with masses ranging between 1 and 10 M⊕ with dimensions up to twice those of Earth. In the right environment, these planets could be the cradle of alien life that could modify the chemical composition of their atmospheres. So, the search for life signatures requires as the first step the knowledge of planet atmospheres, the main objective of future exoplanetary space explorations. Indeed, the quest for the determination of the chemical composition of those planetary atmospheres rises also more general interest than that given by the mere directory of the atmospheric compounds. It opens out to the more general speculation on what such detection might tell us about the presence of life on those planets. As, for now, we have only one example of life in the universe, we are bound to study terrestrial organisms to assess possibilities of life on other planets and guide our search for possible extinct or extant life on other planetary bodies. -
Functional Basis of Microorganism Classification
RESEARCH ARTICLE Functional Basis of Microorganism Classification Chengsheng Zhu1*, Tom O. Delmont2, Timothy M. Vogel2, Yana Bromberg1,3* 1 Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, New Jersey, United States of America, 2 Environmental Microbial Genomics, Laboratoire Ampere, École Centrale de Lyon, Université de Lyon, Ecully, France, 3 Institute for Advanced Study, Technische Universität München, Garching, Germany * [email protected] (CZ); [email protected] (YB) Abstract Correctly identifying nearest “neighbors” of a given microorganism is important in industrial and clinical applications where close relationships imply similar treatment. Microbial classifi- cation based on similarity of physiological and genetic organism traits (polyphasic similarity) OPEN ACCESS is experimentally difficult and, arguably, subjective. Evolutionary relatedness, inferred from Citation: Zhu C, Delmont TO, Vogel TM, Bromberg Y phylogenetic markers, facilitates classification but does not guarantee functional identity (2015) Functional Basis of Microorganism Classification. PLoS Comput Biol 11(8): e1004472. between members of the same taxon or lack of similarity between different taxa. Using over doi:10.1371/journal.pcbi.1004472 thirteen hundred sequenced bacterial genomes, we built a novel function-based microor- Editor: Christine A. Orengo, University College ganism classification scheme, functional-repertoire similarity-based organism network London, UNITED KINGDOM (FuSiON; flattened to fusion). Our scheme is phenetic, based on a network of quantitatively Received: March 27, 2015 defined organism relationships across the known prokaryotic space. It correlates signifi- cantly with the current taxonomy, but the observed discrepancies reveal both (1) the incon- Accepted: July 21, 2015 sistency of functional diversity levels among different taxa and (2) an (unsurprising) bias Published: August 28, 2015 towards prioritizing, for classification purposes, relatively minor traits of particular interest to Copyright: © 2015 Zhu et al.