Difference between archaea and bacteria
Cell wall:
The cell wall of archaea does not contain peptidoglycan. In some archaea there are a number of
polysaccharides and in others, it is composed of purely proteins. Some archea do not possess cell
walls.
Plasma membrane:
The plasma membrane of archaea consists of unusual lipids. The lipids of archaea are composed of
glycerol linked to branch chained hydrocarbons whereas the lipids of bacteria are composed to
glycerol linked to branch chained fatty acids.
Methanogenesis:
The ability to form methane (Methanogenesis) is a form of metabolism something only a few
archaea can do.
Mode of nutrition:
Archaea can use three sources of energy to prepare food.
i.
ii.
iii.
Utilizing sunlight
Utilizing inorganic compounds
Utilizing organic compounds
Ribosomal RNA Sequence:
The major difference between archaea and eubacteria is in the nucleic acid. e.g. near nucleotide
number 910 (out of 1500) researchers noted the following difference
Eubacteria: AAACUCAAA
Archaea: AAACUUAAA
Extreme environments of archaea:
The first prokaryotes that were classified into archaea were all found in extreme environments.
i.
ii.
iii.
Methanogens
Halophiles
Thermoacidophiles
Methanogens:
It is a methane gas producer. It is only found in anaerobic environments such as swamps, marshes
and intestinal tracts of human beings. The methane gas produced is also called biogas.
Halophiles:
It is found in places where no other species can live i.e. fish and meat that has been heavily salted so
that no bacteria can live on it. A large salt concentration is required for growth.
Thermoacidophiles:
They are isolated from extremely hot, acidic environments such as hot springs, geysers and around
volcanoes.
Cyanobacteria:
Cyanobacteria is the most prominent photosynthetic bacteria which can be found in any damp area.
Cyanobacteria is either epiphytic or symbiotic. It possess gram-negative cell wall. Its bodies are
either unicellular or solitary or they are in the form of filaments which can form colonies. In
filamentous form, the cells are in linear form, the trichome is wrapped around mucilage sheath i.e.
Nostoc, anabaena.
Photosynthesis occurs in thylakoid membrane which is present in the outermost layer of cytoplasm
just beneath the cell membrane. Cyanobacteria contains both a-chlorophyll and accessory pigments
such as Phycobilins. Phycocyanin is a blue pigment which is the most prominent accessory pigment.
Like fungi and plants, cyanobacteria uses, carbon dioxide as the carbon source, water as the
hydrogen donor, both photosystems (non-cyclic photophosphorylation) to utilize light energy and to
produce oxygen in the atmosphere. It is believed that oxygen was first introduced into the
atmosphere because of cyanobacteria
Only about one-third of cyanobacteria can fix atmospheric nitrogen. Nitrogen fixation only occurs in
heterocysts which are thick walled cells with no nuclei which are present along the trichome. In
Pakistan, Nostoc and anabaena are used to increase soil fertility because of their nitrogen fixation
ability.