Archaea are a diverse group of microorganisms that inhabit extreme environments. They can be spherical, rod-shaped, or other morphologies, and exist as single cells or aggregates. Archaea are found in environments with high or low temperatures, pH, salt concentrations, or methane levels and can be aerobic, facultative anaerobes, or strictly anaerobes. They play important roles in ecosystems like methanogenesis and sulfate reduction. Archaea have unique cell walls and membranes adapted to extreme conditions like hyperthermophiles that can survive above 100°C. Major groups include methanogens, sulfate reducers, halophiles, and cell wall-less archaea. Archaea have economic importance in areas

1. Archaea
Greek-archaios means ancient

2. Introduction
• Diverse group
• Gram Positive or Gram Negative
• Spherical, lobed, rod-shaped, spiral, cubodial,
triangular, plate shaped, irregularly shaped,
• Pleomorphic
• Present as a single cells, or aggregates / filaments
• Multiplication- binary fission, fragmentation and
other mechanisms
• Physiologically diverse-aerobic, facultative
anaerobes, strictly anaerobes

3. • Chemolithoautotroph, organotroph
• Psychrophiles, mesophiles and hyperthermophiles
(can grow above 1000 c)

4. Ecology
• They live in an extreme environment
• Area with very high or low temperature, PH
• Area with high salt concentration
• Area with high concentration of methane
• Area with no oxygen (anoxic)

5. Volcanic eruptions

6. Amazing Geyser Landscape in
Nevada

7. the vivid red brine (teaming with halophilic
archaebacteria) of Owens

8. Halophiles in sea

9. Great Salt Lake of Utah

10. methanogens may thrive in hot springs

11. Archaeal Cell Wall
• Lack muramic acid and D- amino acids
• Eg. methanogens have peudomurein (a
peptidoglycan like polymer that is cross-linked
with L-amino acids
• Some contain a complex carbohydrate similar to
chondroitin sulfate of animal connective tissue
• Hyperthermophile and methanogens have proten
cell wall

12. Archaeal membrane
• Branched chain hydrocarbon attached to glycerol
by ether
• Thermophile archaea have long tetraether in their
cell membrane. Also pentacyclic rings in HC of
some (help maintain the delicate liquid crystalline
balance of membrane of membrane at high
temperature)
• Other lipids- polar phospholipid, sulfolipid,
glycolipid.

13. Major Archaeal groups
Methanogenic archaea
Archaeal sulfate reducers
Extremely halophilic archaea
Cell wall-less archaea

14. Methanogenic Archaea
• Strict anaerobes
• Produces methane as a major metabolic end
product
• Convert sulfur to hydrogen sulphide wth no energy
production
• They possess co-enzyme M, factor 420/430,
methanopterin
• Eg. Metanobacterim, Methanococcus,
Methanomicrobium, Methanosarcina

15. Archaeal sulfate reducers
• Irregular gram-negative coccoid cells
• Strictly anaerobe and extremely thermophilic
• Hydrogen sulfide is formed from thiosulfate and
sulfate
• Heterotrophic in nature, autotrophic growth with
thiosulfate and hydrogen
• Forms traces of methane
• Possess factor 420 and methanopterin
• Eg. Archeoglobus

17. Extremely halophilic archaea
• Rods, cocci, irregular shaped (pyramid, cube etc)
• Stain gram-positive and gram-negative
• Chemoorganoheterotroph
• Lack peptidogycan
• Most spp. require sodium chloride (> or =15M)
• Mostly produce bright red colonies
• Some unpigmented
• Neutrophilic to alkalophilic
• Generally mesophilic, one sp. is thermophilic
• Possess bacteriorhodopsin and halorhodopsin (
and can use light energy to produce ATP

18. Cell wall-less Archaea
• Pleomorphic cell lacking cell wall
• Thermoacidophilic and chemoorganotrophic
• Facultaive anaerobes
• Mannose-rich glycoprotein and a lipoglycan

19. Extremely thermophilic elementary sulfur
• Gram negative rods, filaments or cocci
• Obligatory thermophile (70-1100 c)
• Usually strictly anaerobe, some are aerobic and
facultative
• Acidophilic and neutrophilic
• Autotrophic or heterotrophic
• Reduction of sulfur to hydrogen sulfide –
anaerobically and hydrogen sulfide or elemental
sulfur oxidized to sulfuric acid aerobically
• eg. Desulfurococcus, Sulfolobus, Thermococcus

20. Economic Importance
• Thermophiles grow in heated water and soil rich in
elemental sulfur and these environment are scattered
all over the world. Eg. Sulfur rich hot springs in
Yellowstone National Park
• Methanogens produce methane using sewage sludge,
which is a clean burning fuel(pollution free energy)
• Methane production can contribute to global warming
• Halophiles are used in the production of many salted
food products, including soysauce
• Thermoplasma oxidizes iron sulfide (in piles of coal
mines) to sulfuric acid. As a result piles become hot
and acidic

21. Yellowstone National Park