archea - overview and major types .pptx

Archea are prokaryotes. They are microscopic, unicellular prokaryotic microorganisms. These have many characters similar to the bacteria and hence earlier, these microorganisms were classified along with

1. archea

2. The Archaebacteria: prokaryotes do not have peptidoglycan in their cell walls have unique lipids in their plasma (cell) membranes

3. The Archaebacteria also: have some genes that resemble eukaryotic genes usually are not pathogenic (they don’t usually make us sick!) live in extreme environments: high concentrations of salt extremes of pH and temperature

4. Archaea [Greek archaios , ancient] stain either gram positive or gram negative spherical, rod-shaped, spiral, lobed, plate-shaped, irregularly shaped, or pleomorphic Occur singly or form filaments or aggregates. diameter from 0.1µ to over 15µ m, and some filaments can grow up to 200 µm in length

5. Multiplication may be by binary fission, budding, fragmentation, or other mechanisms extreme aquatic and terrestrial habitats

6. Bac Archea Eukarya

7. wall structure and chemistry differ from that of the bacteria Gram-positive archaea can have a variety of complex polymers in their walls. Methanobacterium and some other methanogens have walls containing pseudomurein, a peptidoglycan like polymer that has L-amino acids in its cross-links, N- acetyltalosaminuronic acid instead of N- acetylmuramic acid, and (1→3) glycosidic bonds instead of (1 →4) glycosidic bonds

8. Methanosarcina and Halococcus lack pseudomurein and contain complex polysaccharides similar to the chondroitin sulfate Some hyperthermophiles and metanogens have protein CW

9. Cell Membrane branched chain hydrocarbons attached to glycerol by ether linkages. -> form diether Some Thermophilic archaea - link two glycerol groups to form long tetraethers . Diether side chains are usually 20 carbons long, and tetraether chains contain 40 carbon atoms. can adjust chain lengths by cyclizing the chains to form pentacyclic rings. maintain the delicate liquid crystalline balance of the membrane at high temperatures. Polar phospholipids, sulfolipids , and glycolipids are also found

10. Thermoplasma and Sulfolobus are almost completely tetraether monolayers.

11. Energy Conservation and Autotrophy in Archaea Chemoorganotrophy and chemolithotrophy ▪ With the exception of methanogenesis , bioenergetics and intermediary metabolism of Archaea are similar to those found in Bacteria - Glucose metabolism : EMP or slightly modified Entner-Doudoroff pathway - Oxidation of acetate to CO 2 : TCA cycle or some slight variations of TCA cycle : Reverse route of acetyl- CoA pathway

12. - Electron transport chains with a, b , and c -type cytochromes present in some Archaea : use O 2 , S , or some other electron acceptor (nitrate or fumarate ) : establish proton motive force : ATP synthesis through membrane-bound ATPase - Chemolithotrophy : H 2 as a common electron donor and energy source is well established

13. ▪ Autotrophy via several different pathways is widespread in Archaea ▪ acetyl- CoA pathway in methanogens and most hyperthermophiles ▪ Reverse TCA cycle in some hyperthermophiles ▪ Calvin cycle in Methanococcus jannaschii and a Pyrococcus species (both are hyperthermophiles )

14. Phylogenetic Overview of Archaea Archaea share many characteristics with both Bacteria and Eukarya Archaea are split into two major groups (phyla) Crenarchaeota Euryarchaeota

15. Detailed Phylogenetic Tree of the Archaea Figure 17.1

16. 3 Major Archaebacterial Groups Methanogens Halophiles Hyperthermophiles

17. Phylum Crenarchaeota are extremely thermophilic , and many are acidophiles and sulfur dependent. The sulfur may be used either as an electron acceptor in anaerobic respiration or as an electron source by lithotrophs Almost all are strict anaerobes.

18. Habitats of Hyperthermophilic Archaea Figure 17.16a A typical Solfatara in Yellowstone National Park

19. Figure 17.16b Sulfur-rich hot spring

20. Figure 17.16c A typical boiling spring of neutral pH in Yellowstone Park; Imperial Geyser

21. Figure 17.16d An acidic iron-rich geothermal spring

22. Pyrodictium isolated from geothermally heated sea floors. has a temperature minimum of 82°C, a growth optimum at 105°C , and a maximum at 110°C . Both organotrophic and lithotrophic growth Sulfur and H2 - common electron sources for lithotrophs

23. Sulfolobus are gram-negative, aerobic, irregularly lobed spherical a temperature optimum around 70 to 80°C and a pH optimum of 2 to 3 - thermoacidophiles , CW- lipoprotein and carbohydrate but lacks peptidoglycan . lithotrophic on sulfur granules in hot acid springs and soils while oxidizing the sulfur Oxygen is the normal electron acceptor, but ferric iron may be used . Sugars and amino acids such as glutamate also serve as carbon and energy sources .

24. Sulfolobus

25. Thermoproteus is a long thin rod that can be bent or branched Its cell wall is composed of glycoprotein. strict anaerobe and grows at temperatures from 70 to 97°C and pH values between 2.5 and 6.5 . Hot springs and other hot aquatic habitats rich in sulfur . organotrophically - glucose, amino acids, alcohols, and organic acids elemental sulfur as the electron acceptor- anaerobic respiration chemolithotrophically using H2 and S0. Carbon monoxide or CO2 can serve as the sole carbon source

26. Thermoproteus

27. Phylum Euryarchaeota

28. Methanogens are strict anaerobes that obtain energy by converting CO2 , H2, formate , methanol, etc to either methane or methane and CO2 growing on H2 and CO2- are autotrophic This is the largest group of archaea . anaerobic environments rich in organic matter : the rumen and intestinal system of animals, freshwater and marine sediments, swamps and marshes, hot springs, anaerobic sludge digesters, and even within anaerobic protozoa

29. are five orders ( Methanobacteriales , Methanococcales , Methanomicrobiales , Methanosarcinales , and Methanopyrales three different types of cell walls- pseudomurein , proteins or heteropolysaccharides contain several unique cofactors : tetrahydromethanopterin (H4MPT ), methanofuran (MFR), coenzyme M, (2-mercaptoethanesulfonic acid), coenzyme F420, and coenzyme F430

30. Extremely Halophilic Archaea Haloarchaea Extremely halophilic Archaea Have a requirement for high salt concentrations Typically require at least 1.5 M (~9%) NaCl for growth Up to 23-36% Found in solar salt evaporation ponds, salt lakes, and artificial saline habitats (i.e., salted foods)

31. Hypersaline Habitats for Halophilic Archaea Figure 17.2a Great Salt Lake, Utah

32. Figure 17.2b Seawater Evaporating Ponds Near San Francisco Bay, California

33. Figure 17.2c Pigmented Haloalkaliphiles Growing in pH 10 Soda Lake in Egypt

34. Figure 17.2d SEM of Halophilic Bacteria

35. Halobacterium salinarium trap light energy photosynthetically without the presence of chlorophyll. low oxygen concentrations- synthesize modified cell membrane called the purple membrane, which contains the protein bacteriorhodopsin .

36. Halobacterium actually has four rhodopsins , each with a different function. bacteriorhodopsin drives outward proton transport for purposes of ATP synthesis. Halorhodopsin uses light energy to transport chloride ions into the cell and maintain a 4 to 5 M intracellular KCl concentration. Two rhodopsins that act as photoreceptors , one for red light and one for blue . They control flagellar activity to position the organism optimally in the water column

37. Thermoplasms class Thermoplasmata – thermoacidophiles that lack cell walls. At present, only two genera, Thermoplasma and Picrophilus , are known. Thermoplasma - grows best at 55 to 59°C and pH 1 to 2. ; grows in refuse piles of coal mines- large amounts of iron pyrite ( FeS ), which is oxidized to sulfuric acid by chemolithotrophic bacteria. lacks a cell wall , its plasma membrane is strengthened by large quantities of diglycerol tetraethers , lipopolysaccharides , and glycoproteins . The organism’s DNA is stabilized by association with a special histone -like protein At 59°C, Thermoplasma takes the form of an irregular filament, whereas at lower temperatures it is spherical- Pleomorphic The cells may be flagellated and motile.

38. Picrophilus - lacks a regular cell wall, has an S-layer outside its plasma membrane. irregularly shaped cocci , large cytoplasmic cavities that are not membrane bounded. is aerobic and grows between 47 and 65°C with an optimum of 60°C. organism will grow only below pH 3.5 and has a growth optimum at pH 0.7. Growth actually occurs at about pH 0!

39. Extremely Thermophilic S0-Metabolizers This physiological group contains the class Thermococci , with one order, Thermococcales . The Thermococcales are strictly anaerobic and can reduce sulfur to sulfide. They are motile by flagella optimum growth temperatures around 88 to 100°C. one family and two genera, Thermococcus and Pyrococcus .

40. Sulfate-Reducing Archaea class Archaeoglobi one genus- Archaeoglobus gram-negative, irregular coccoid cells with walls consisting of glycoprotein subunits. variety of electron donors (e.g., H2, lactate, glucose) and reduce sulfate, sulfite, or thiosulfate to sulfide. Elemental sulfur is not used as an acceptor extremely thermophilic (the optimum is about 83°C) able to reduce sulfate, also possesses the methanogen coenzymes F420 and methanopterin