Archaebacteria means "ancient bacteria". They were the only organisms on the planet for millions of years. They are still present with their primitive characters so they are the "Oldest living fossils". They are adapted to life in regions where no other living thing can survive.
Characteristics Of Archaebacteria
- Mostly they are obligate anaerobes. They cannot tolerate the presence of oxygen.
- Cell wall of archaebacteria lack peptidoglycan (murein). They have pseudopeptidoglycan. It is different from bacterial peptidoglycan in chemical structure, but resembles in function. Human lysozyme can degrade peptidoglycan but ineffective on pseudopeptidoglycan.
- Further branched chain ether linked lipid are present in plasma membrane of archaebacteria, due to which these can face extreme of conditions of temperature and pH.
Types Of Archaebacteria
Archaebacteria can classified into three categories on the basis of home environments: Methanogens, Thermoacidophiles and Halophiles.
- Methane producing bacteria
- These bacteria convert CO2 of swampy areas into methane.
- These bacteria convert the organic substance present in cow dung into methane by fermentation. (Gobas gas fermenter) Example: Methanococcus.
- They are also present in the rumen of cattle, where it digests the cellulose by fermentation and convert it into methane. Example: Rumenococcus
- Halphiles means Salt loving.
- They are found in extreme salty areas such as the Great Salt Lake and the Dead Sea.
- Halophiles are surrounded by purple membrane in which a pigment, bacteriorhodopsin is found due to this reason membrane absorbs the bright light and directly forms ATP i.e. they cannot prepare food like eubacteria. Instead of it they directly form ATP. Therefore They are non photosynthetic.
- Thermoacidophiles means heat and acid loving.
- These archaebacteria are found at those places where temperature is approx 80oC – 100oC and medium is acidic.
- These are aerobic bacteria, which have the capacity to oxidise sulphur to H2SO4 at high temperature and high acidity.
- Some of these bacteria are able to reduce sulphur to H2S under anerobic conditions.
- They are found in hot sulphur springs such as Yellowstone National park.