Trinity College Dublin: Diversity of Life - The Archaea PDF

Diversity of Life The Archaea Dr A. Fleming  Overview of lecture: The Archaea What you will learn: Archaea form a distinct domain of life They are Prokaryotic microorganisms Cell structure & function Contain extremophiles...

Diversity of Life The Archaea Dr A. Fleming  Overview of lecture: The Archaea What you will learn: Archaea form a distinct domain of life They are Prokaryotic microorganisms Cell structure & function Contain extremophiles Habitat  The Archaea Carl Woese US scientist (1928-2012) LUCA (last unknown common ancestor) Originally described as bacteria A third domain of life (16S rRNA sequencing) The Archaea are prokaryotes No nucleus Circular chromosome No cell organelles The Archaea evolved separately from bacteria Archaea (3.8 bya) Archaea bya Archaea and Bacteria diverged and formed separate domains  Archaea cell morphology Range in size from 0.1 – 200 μm Haloquadratum Methanococcus Walsbyi Janaschii -square ! -cocci with flagella Methanosarcina Methanothermus Barkeri fervidus -lobed cocci -Short bacillus Methanobacterium Thermoautotrophicum -filamentous  Archaea cell wall composition varies Polysaccharide Protein Glycoproteins Mixture of all these macromolecules No cell wall Archaeal cell walls do not contain peptidoglycan Archaea cell wall composition varies Halococcus salifodinae Glycoprotein Methanosarcina barkeri Methanochondriotin Pseudomurein is structurally similar to peptidoglycan Amino-sugar backbone (L-isomers) Methanobrevibacter ruminantium Pseudomurein has some significant differences to peptidoglycan Insensitive to Penicillin The S-layer is the most common cell wall in Archaea Methanocaldococcus jannaschii - Cell wall is entirely an S-layer TEM: S-layer fragment Protein/glycoprotein Crystalline structure Can accompany other cell wall components  Archaeal cell membranes are unique Bacterial/Eukaryotic cell membrane: Hydrophobic tail Ester linkage Phospholipid: Hydrophylic head Phospholipid bilayer Ester linkages bond fatty acids to glycerol Archaeal cell membrane lipids are unique The lipid tail is NOT a fatty acid The lipid tails vary in structure An ether linkage bonds the lipid tail and glycerol Archaeal cell membranes have unique structures Lipid bi-layer Lipid mono-layer The lipids can form bi- or mono-layers impart distinct membrane properties Unique archaeal cell surface structures: Hami Hami A Hamus ‘grappling hook’ A network of hami: Biofilm formation Pili-like structures called ‘hami’ For attachment Archaea have unique flagella: Archaella ATP Rotate to drive motility Smaller than bacterial flagella What is the fastest* organism on Earth? Usain Bolt (27.8 mph) Cheetah (70 mph) Methanocaldococcus Jannaschii (500 cell lengths/s)*  Archaeal cell growth Halobacterium salinarum Binary fission Genetically identical daughter cells (asexual) Many Archaea cannot be cultured in the lab !  Archaeal metabolism is diverse Aerobic: Anaerobic: use oxygen Do not need oxygen Phototrophic: Halobacterium salinarum Haloquadratum Out Light In Walsbyi Cytoplasmic Methanobrevibacter membrane ruminantium Bacteriorhodopsin ATP ATPase Thermoplasma volcanium (Facultative aerobe) Not photosynthesis No CO2 fixation  Archaeal habitats Originally identified in extreme environments Extremophiles – Hyperthermophiles – Methanogens – Extreme halophiles Halophile habitat and structure Resistant to high salt concentrations  Halophile habitat and structure Halophile: Requires 9% - 32% NaCl for growth Habitats: salt lakes Fish Salted food (pork) Sea water evaporation pond (California) SEM of square Archaea Halophile cytoplasm is osmotically balanced Halobacterium salinarum High NaCl K+ ions K+ + K+ K Potassium cations are accumulated Balances the osmotic forces Maintains cell water content  Halophile cell structure Halobacterium salinarum Glycoprotein cell wall Cell wall is complexed with Na+ cations Required for cell wall integrity  Halophile cell structure Haloquadratum Walsbyi Halobacterium cells are thin (0.1 um) Strict aerobes Contains gas vesicles Cell floats Thermophiles and hyperthermophiles Different organisms display distinct growth optima Hyperthermophiles grow best at >100oC  Thermophiles and hyperthermophiles Found in terrestrial / submarine geothermal habitats Underwater hydrothermal vent Hot springs (< 100oC) (> 100oC) Boiling springs (=100oC) Growth optima of hyperthermophiles is > 100oC The most thermophilic organisms are found in submarine volcanic habitats Submarine vents are under pressure Water > 100oC Organisms live on the inner walls Pyrolobus fumarii Growth optima = 106oC Black Smoker Pyrolobus fumarri can withstand autoclaving (121oC) for 1h Pyrolobus fumarii 121oC/30 min Autoclaving kills endospores after 15 min at 121oC No archaea are known to be pathogenic ‘Strain 121’ actually grows at 121oC Strain 121 Geogemma barossii Coccoid cells Displays archaella Strict anaerobe Can survive for 2h at 130oC It cannot live below 90oC The world record holding hyperthermophile (so far…….) 8 x 0.5 um geranylgeraniol Methanopyrus kandleri Growth has been recorded at 122oC Generation time of 1h at 100oC Has a novel membrane lipid What is the upper temperature limit for life? 150oC ???? Psychrophiles: found in cold regions  Barophiles: Found at the bottom of the ocean Resistant to extreme pressures  Not all archaea are extremophiles 20% of prokaryotes in the ocean 1% of all soil microbes Perform important geo-biochemical reactions Contribute to the Nitrogen cycle (fix N2)  Could life exist on other planets ? Europa is a moon of Jupiter It is encased in water ice Volcanoes could be active Did life on earth arrive from outer space ? Comets & Meteorites Sir Fred Hoyle (1915 – 2001) Has life on earth spread to outer space ? Alien life ? ? Archaea – like ? Could Archaea be the future of life on earth ?  Summary Archaea are prokaryotes The Archaea form a third way of life They have unique cell walls They have unique cell membranes Diverse metabolism Diverse habitats Contain many extremophiles Contain no known pathogens  Extra Reading: Campbell Biology or any good Microbiology textbook: e.g. Brock biology of Microorganisms or Prescott’s Microbiology