Archaebacteria is the most primitive and ancient bacteria. They
are supposed to be oldest of the living fossils. They possess a unique cell
wall that consists of polysaccharide and protein. They lack peptidoglycan
(murein). The cell membrane contains branched-chain lipids, which enable them
to withstand extremes of heat, high PH, absence of oxygen and high
concentration.
Based upon
ecological properties , the archaebacteria can be classified into three groups
:
1. Thermoacidophiles (Temperature and acid
loving) : They are
aerobic forms of bacteria found in hot sulphur springs. They are high
temperature and acid loving cyanobacteria. At 80 C, they oxidize sulphur to
sulphuric acid in highly acidic medium. Under aerobic condition , these
sulphur-dependent bacteria are called thermoacidophiles. These can reduce
sulphur to H2S under anaerobic conditions.
2. Methanogens (Methane producers) : These are anaerobic archaebacteria which
occur in marshy places and convert the formic acid or CO2 to methane. In biogas
plants, they produce the methane gas, which is used as fuel.
3. Halophiles (Salt loving) : These are anaerobic bacteria which occur
at salt rich soils. They prepare pigmented membrane in the presence of sunlight.
This process is different from that of eukaryotic photosynthesis.
0 comments: