Archaebacteria

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Archaebacteria

  1. 1. ARCHAEBACTERIA
  2. 2. CONTENTS <ul><li>Introduction </li></ul><ul><li>Archaeal cell walls </li></ul><ul><li>Archaeal lipids & membranes </li></ul><ul><li>Genetics & molecular biology </li></ul><ul><li>Metabolism </li></ul><ul><li>Archaeal taxonomy </li></ul><ul><li>Significance of Archaebacteria </li></ul><ul><li>References </li></ul>
  3. 3. Introduction
  4. 4. Introduction to the Archaea <ul><li>Morphology </li></ul><ul><ul><ul><li>Stain either Gram +ve or Gram –ve </li></ul></ul></ul><ul><ul><ul><li>Shapes – Spherical, rod, spiral, lobed, irregularly shaped or pleomorphic </li></ul></ul></ul><ul><ul><ul><li>Single cells or filaments or aggregates, diameter from 0.1 to over 15 μ m </li></ul></ul></ul><ul><ul><ul><li>Multiplication – binary fission, budding, fragmentation or other mechanisms </li></ul></ul></ul>Contd…
  5. 5. <ul><li>Physiology </li></ul><ul><ul><ul><li>Aerobic, facultative and strictly anaerobic </li></ul></ul></ul><ul><ul><ul><li>Range from chemolithotrophs to organotrophs </li></ul></ul></ul><ul><ul><ul><li>Mesophilic & hyperthermophiles </li></ul></ul></ul><ul><ul><ul><li>Found in extreme environments </li></ul></ul></ul><ul><ul><ul><li>Few are symbionts in animal digestive system </li></ul></ul></ul>Contd…
  6. 6. Archaeal cell walls
  7. 7. Structure <ul><li>Gram +ve Archaea </li></ul><ul><ul><ul><li>Single thick homogenous layer as in Gram +ve bacteria </li></ul></ul></ul><ul><li>Gram +ve Archaea </li></ul><ul><ul><ul><li>lack outer membrane & complex peptidoglycan network </li></ul></ul></ul><ul><ul><ul><li>have a surface layer of proteins or glycoproteins </li></ul></ul></ul>Contd…
  8. 8. Chemistry <ul><li>Gram +ve Archaea </li></ul><ul><ul><ul><li>Variety of complex polymers </li></ul></ul></ul><ul><ul><ul><li>Methanobacterium – pseudomurein </li></ul></ul></ul><ul><ul><ul><li>Methanosarcina & Halococcus – complex polysaccharides similar to chondroitin sulphate of animal connective tissue </li></ul></ul></ul><ul><ul><ul><li>Other heteropolysaccharides are also found </li></ul></ul></ul>Contd…
  9. 9. <ul><li>Gram -ve Archaea </li></ul><ul><ul><ul><li>Layer of protein or glycoprotein outside their PM (20 to 40 nm thick) </li></ul></ul></ul><ul><ul><ul><li>Methanolobus, Halobacterium & several extreme thermophiles ( Sulfolobus, Thermoproteus & Pyrodictium ) consist of glycoprotein units </li></ul></ul></ul><ul><ul><ul><li>Methanococcus, Metahnomicrobium, Methanogenium & Desulfurococcus consist of protein units </li></ul></ul></ul>Contd…
  10. 10. Archaeal Lipids & Membranes
  11. 11. <ul><ul><ul><li>Branched chain hydrocarbon attached to glycerol by ether links rather than fatty acids joined by ester links </li></ul></ul></ul><ul><ul><ul><li>Sometimes two glycerol groups – form an extremely long tetraether (40C) </li></ul></ul></ul><ul><ul><ul><li>Length is adjusted by cyclizing the chain to form pentacyclic rings </li></ul></ul></ul><ul><ul><ul><li>Polar lipids like phospholipids, sulfolipids & glycolipids are present </li></ul></ul></ul><ul><ul><ul><li>7 to 30% are non polar lipids </li></ul></ul></ul>Contd…
  12. 12. <ul><ul><ul><li>lipids can be combined in various ways – membranes of different rigidity </li></ul></ul></ul><ul><ul><ul><ul><li>C20 diethers – regular bilayer membrane </li></ul></ul></ul></ul><ul><ul><ul><ul><li>C40 tetraether – much more rigid monolayer membrane </li></ul></ul></ul></ul>Contd…
  13. 13. Genetics & Molecular Biology
  14. 14. <ul><ul><ul><li>Circular DNA – like bacteria </li></ul></ul></ul><ul><ul><ul><li>Genomes are significantly smaller than bacteria. </li></ul></ul></ul><ul><ul><ul><ul><li>E. coli – 2.5 x 10 9 Daltons </li></ul></ul></ul></ul><ul><ul><ul><ul><li>T. acidophilum – 0.8 x 10 9 Daltons </li></ul></ul></ul></ul><ul><ul><ul><li>G + C content varies from 21 - 68 mol % </li></ul></ul></ul><ul><ul><ul><li>mRNA – similar to bacterial mRNA </li></ul></ul></ul><ul><ul><ul><li>T ψ C arm of tRNA – pseudouridine / 1-methyl pseudouridine </li></ul></ul></ul>Contd…
  15. 15. <ul><ul><ul><li>Sensitive to anisomycin & insensitive to chloramphenicol & kanamycin </li></ul></ul></ul><ul><ul><ul><li>EF-2 reacts with diphtheria toxin </li></ul></ul></ul><ul><ul><ul><li>Many methanogens - nucleosomes </li></ul></ul></ul><ul><ul><ul><li>DNA dependent polymerases resemble eukaryotic enzymes rather than prokaryotic polymerases </li></ul></ul></ul>Contd…
  16. 16. Metabolism
  17. 17. <ul><ul><ul><li>CH metabolism is best understood </li></ul></ul></ul><ul><ul><ul><li>6- phosphofructokinase is absent & E-M p/w is not followed </li></ul></ul></ul><ul><ul><ul><li>Extreme halophiles & thermophiles – modified form of E-D p/w wherein initial intermediates are not phosphorylated </li></ul></ul></ul><ul><ul><ul><li>Methanogens do not catabolise glucose </li></ul></ul></ul><ul><ul><ul><li>Gluconeogenesis – reversal of E-M p/w </li></ul></ul></ul><ul><ul><ul><li>All oxidize pyruvate – acetyl coA using pyruvate oxidoreductase </li></ul></ul></ul>Contd…
  18. 18. <ul><ul><ul><li>Biosynthetic p/w – similar to those in other organisms </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Some methanogens can fix atmospheric N 2 </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Few employ glycogen as the main reserve material </li></ul></ul></ul></ul></ul><ul><ul><ul><li>Autotrophy is widespread among methanogens & extreme thermophiles </li></ul></ul></ul><ul><ul><ul><li>Thermoproteus & Sulfolobus – fix CO 2 by reductive TCA cycle </li></ul></ul></ul><ul><ul><ul><li>Methanogens & extreme thermophiles –fix CO 2 by reductive acetyl coA p/w </li></ul></ul></ul>Contd…
  19. 19. Reductive TCA cycle Contd…
  20. 20. Archaeal Taxonomy
  21. 21. Phylum Crenarchaeota <ul><ul><ul><li>Most are extremely thermophilic & many are acidophiles and S dependent </li></ul></ul></ul><ul><ul><ul><li>S – as electron acceptor or electron source by lithotrophs </li></ul></ul></ul><ul><ul><ul><li>Almost all are strict anaerobes & grow in geothermally heated water / soils that contain elemental sulfur </li></ul></ul></ul>Contd…
  22. 22. <ul><ul><ul><li>Divided into one class – Thermoprotrei & three orders : </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Thermoproteales </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Sulfolobales </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Desulfurococcales </li></ul></ul></ul></ul></ul><ul><ul><ul><li>Contain 69 genera – two of the better studied genera are Thermoproteus & Sulfolobus </li></ul></ul></ul>Contd…
  23. 23. <ul><li>Sulfolobus </li></ul><ul><li>Gram –ve, aerobic, irregularly lobed spherical archaeons </li></ul><ul><li>Optimum temp.– 70 to 80 0 C & optimum pH 2 - 3 </li></ul><ul><li>hence also referred to as thermoacidophiles </li></ul><ul><li>Cell wall – lipoprotein & CH, lacks peptidoglycan </li></ul><ul><li>Grow lithotrophically on S granules in hot S springs oxidizing S to Sulfuric acid </li></ul><ul><li>Oxygen Is the normal electron acceptor, Fe +3 may be used </li></ul>Contd…
  24. 24. <ul><li>Sugars & amino acids (glutamate) also serve as C & energy sources </li></ul>Contd…
  25. 25. <ul><li>Thermoproteus </li></ul><ul><li>Gram –ve, strictly anaerobic, hyperthermophilic long thin rod, can be bent or branched </li></ul><ul><li>Cell wall consists of glycoprotein </li></ul><ul><li>Grows at temp. from 70 - 97 0 C & pH 2.5 – 6.5 </li></ul><ul><li>Found in hot springs & other hot aquatic habitats rich in sulfur </li></ul><ul><li>Can grow organotrophically & oxidize glucose, amino acids, alcohols & organic acids with S as TEA </li></ul>Contd…
  26. 26. An aquatic spring in Japan with Thermoproteus growth <ul><li>Grows chemolithtrophically using Hydrogen & S 0 </li></ul><ul><li>CO & CO 2 can serve as the sole C source </li></ul>Thermoproteus Contd…
  27. 27. Phylum Euryarchaeota <ul><li>Very diverse with 7 classes viz. Methanococcus, Methanobacteria, Halobacteria, Thermoplasmata, Thermococci, Archaeglobi & Methanopyri </li></ul><ul><li>Consists of 9 orders & 15 families </li></ul><ul><li>Includes methanogens, extreme halophiles, sulphate reducers & many extreme thermophiles with S dependent metabolism </li></ul>Contd…
  28. 28. <ul><li>The Methanogens </li></ul><ul><li>Strict anaerobes that obtain energy by converting CO 2 , H 2 , formate, methanol, acetate & other compounds to either CH 4 or CH 4 & CO 2 </li></ul><ul><li>Autotrophic when growing on CO 2 & H 2 </li></ul><ul><li>5 orders ( Methanobacteriales, Methanococcales, Methanomicrobiales, Methanosarcinales & Methanopyrales) & 26 genera </li></ul><ul><li>Metabolism is unusual </li></ul><ul><ul><ul><li>Unique cofactors like H 4 MPT, MFR, Coenzyme M Coenzyme F 420 , Coenzyme F 430 </li></ul></ul></ul><ul><ul><ul><li>Coenzyme F 420 carries electrons and Hydrogen </li></ul></ul></ul><ul><ul><ul><li>Coenzyme F 430 cofactor for methyl co-M methyl reductase </li></ul></ul></ul>Contd…
  29. 29. Methane synthesis from CO 2 by Methanobacterium thermoautotrophicum Contd…
  30. 30. <ul><li>Some live autotrophically – acetyl coA from two molecules of CO 2 & then converting acetyl coA to pyruvate & other products </li></ul><ul><li>Found in anaerobic environment rich in organic matter </li></ul><ul><ul><ul><li>Rumen & intestine of animals, fresh water & marine sediments, swamps & marshes, hot springs, anaerobic sludge digesters & anaerobic protozoa </li></ul></ul></ul><ul><li>Ecological significance </li></ul><ul><ul><ul><li>Cow belches 200 – 400 ltrs CH 4 /day </li></ul></ul></ul><ul><ul><ul><li>Source of energy for sewage treatment plants </li></ul></ul></ul>Contd…
  31. 31. E.g. Halobacterium salinarium <ul><li>Unusual type of photosynthesis </li></ul><ul><li>On exposure to sunlight – purple membrane – bacteriorhodopsin </li></ul><ul><li>Four types of rhodopsins </li></ul><ul><ul><ul><li>Bacteriorhodopsin – proton transport for ATP synthesis </li></ul></ul></ul><ul><ul><ul><li>Halorhodopsin – uses light energy to transport chloride ions into the cell & maintains KCl conc. </li></ul></ul></ul><ul><ul><ul><li>Remaining two – photoreceptors, one for red light & one for blue </li></ul></ul></ul>Contd…
  32. 32. <ul><li>Ecological hazards </li></ul><ul><ul><ul><li>Methane gas – Greenhouse gas </li></ul></ul></ul><ul><ul><ul><li>Can oxidize Fe 0 </li></ul></ul></ul><ul><ul><ul><li>May contribute to corrosion of buried or submerged iron pipes </li></ul></ul></ul>Yellowstone National Park M. thermoautotrophicum Contd…
  33. 33. <ul><li>The Halobacteria </li></ul><ul><li>Class Halobacteria – 15 genera in one family, the Halobacteriaceae </li></ul><ul><li>Aerobic chemoheterotrophs with respiratory metabolism </li></ul><ul><li>Non motile or motile by lophotrichous flagella </li></ul><ul><li>Absolutely dependent on high NaCl conc. </li></ul><ul><ul><ul><li>At least 1.5 M NaCl, growth optimum at 3 – 4 M </li></ul></ul></ul><ul><ul><ul><li>Cell wall disintegrates below 1.5 M conc. </li></ul></ul></ul><ul><ul><ul><li>Grow only in high salinity habitats </li></ul></ul></ul><ul><ul><ul><li>Cause spoilage of salted fish </li></ul></ul></ul>Contd…
  34. 34. Purple lake in Australia H. salinarium Contd…
  35. 35. <ul><li>The Thermoplasms </li></ul><ul><li>Class Thermoplasmata </li></ul><ul><li>Thermoacidophiles that lack cell wall </li></ul><ul><li>Two genera, Thermoplasma & Pichrophilus </li></ul><ul><li>Thermoplasma </li></ul><ul><ul><ul><li>Grows in refuse piles of coal mines </li></ul></ul></ul><ul><ul><ul><li>Temperatures from 55 – 59 0 C & pH 1-2 </li></ul></ul></ul><ul><ul><ul><li>Plasma membrane is strengthened by large quantities of diglycerol, tetraethers, lipopolysaccharides & glycolipids </li></ul></ul></ul><ul><ul><ul><li>DNA stabilized by nucleosomes </li></ul></ul></ul>Contd…
  36. 36. <ul><ul><ul><li>At 59 0 C - irregularly shaped & at lower temperatures – spherical </li></ul></ul></ul><ul><ul><ul><li>May be motile by flagella </li></ul></ul></ul>Contd…
  37. 37. <ul><li>Picrophilus </li></ul><ul><ul><ul><li>Lacks cell wall , has S layer outside PM </li></ul></ul></ul><ul><ul><ul><li>Aerobic, irregularly shaped cocci, 1 – 1.5 μ m in diameter </li></ul></ul></ul><ul><ul><ul><li>Temp. range 47 – 65 0 C, optimum temp. 60 0 C </li></ul></ul></ul><ul><ul><ul><li>pH below 3.5, optimum pH 0.7 </li></ul></ul></ul><ul><ul><ul><li>Can grow at pH 0 </li></ul></ul></ul>Contd…
  38. 38. <ul><li>Extremely Thermophilic S 0 Metabolizers </li></ul><ul><li>Class Thermococci, order Thermococcales </li></ul><ul><li>Strictly anaerobic </li></ul><ul><li>Reduce sulfur to sulfide </li></ul><ul><li>Motile by flagella </li></ul><ul><li>Optimum growth temp. 88 –100 0 C </li></ul><ul><li>Two genera, Thermococcus & Pyrococcus </li></ul>Contd…
  39. 39. <ul><li>Sulfate Reducing Archaea </li></ul><ul><li>Class Archaeglobi, order Archaeoglobales </li></ul><ul><li>Gram –ve, irregular coccoid cells </li></ul><ul><li>Cell wall – glycoprotein subunits </li></ul><ul><li>Electron sources – hydrogen, lactate & glucose, reduce sulfate, sulfite or thiosulfate to sulfide </li></ul><ul><li>S is not used as electron acceptor </li></ul><ul><li>Extremely thermophilic, optimum temp. around 83 0 C, occur in hydrothermal vents </li></ul>Contd…
  40. 40. Significance of Archaea
  41. 41. <ul><li>Methanogens are used for the production of methane which is a rich source of energy </li></ul><ul><li>Preparation of glycoproteins & proteins from archaeal cultures are used to increase body’s defense against infection </li></ul><ul><li>Halophilic archaea are used to prescreen antitumor drugs active on eukaryotic proteins </li></ul><ul><li>Thermophilic archaea are used in PCR </li></ul>
  42. 42. References <ul><li>Prescott, Lansing M.; Harley, John P. and Klein, Donald A.,2003. Microbiology, 5 th edition. McGraw – Hill </li></ul><ul><li>www.euarch.blogspot.com </li></ul><ul><li>www.filebox.vt.edu </li></ul><ul><li>www.nature.com/ntmicro/journal/v5/n4 </li></ul><ul><li>www.fib_tab/nrmicro1619_F3.html </li></ul><ul><li>www.microbewiki.kenyon.edu/ </li></ul>

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