Archaebacteria are ancient bacteria that may have evolved immediately after the origin of life on Earth. They are the oldest "living fossils" and are a heterogeneous group found in extreme environments with high pH, temperature, or salinity. Archaebacteria show variation in cell wall structure and composition, containing proteins, glycoproteins, or polysaccharides instead of peptidoglycan. Their cell membranes also contain branched lipids that allow them to withstand extreme conditions. There are three main types: methanogens that produce methane in marshes; halophiles that thrive in highly saline solutions; and thermoacidophiles found in acidic hot springs that tolerate high heat and acidity.

1. ARCHAEBACTERIA
Dr. Saji Mariam George
Associate Professor,
Assumption College Autonomous
Changanacherry

2. ARCHAEBACTERIA
• Ancient bacteria – might have evolved
immediately after the origin of life on earth.
• Oldest “living fossils”.
• A heterogeneous group of bacteria which
differ from each other in morphology,
chemical composition, metabolism and
habitat.
• Found in extreme environments having high
pH, temperature, salinity etc.

3. • Show much variation in cell wall structure
• They may be either Gram - positive or Gram –
negative.
• There is no common cell wall polymer – do not
contain Peptidoglycan
Cell wall may be composed of
i. Proteins (e.g. Desulphurococcus )
ii. Glycoproteins (e.g. Thermoproteus )
iii. Polysaccharides (e.g. Halococcus)

4. • Cell membranes in Archaebacteria contain
branched chain lipids – enable them to bear
extreme temperature and pH.
• Obligate anaerobes or facultative anaerobes.

5. TYPES OF ARCHAEBACTERIA
1) Methanogens (Methane producers )
egs : Methanobacterium , Methanococcus.
• Strict anaerobes
• Found in marshy areas
• Produce methane from carbon dioxide and
formic acid

6. 2 ) Halophiles (Salt lovers)
egs. Halococcus, Halobacterium
• Found in extremly strong salt solutions
• They are mostly aerobic

7. 3) Thermoacidophiles
egs. Thermoplasma, Thermoproteus
• Found in acidic hot springs
• They can tolerate high temperature and
acidity.
• Mostly aerobic.

8. THANK YOU