Write a short note on Archaebacteria …

Archaebacteria are the most primitive bacteria, probably by the first form of life, which evolved in a different line from that of true bacteria. These are adapted to extreme conditions like an oxygeny, pH, salinity and temperature. They differ from true bacteria by cell wall lacks murein, cell membrane with lipids (glycerol isopronyl ether) of branched alipathic chains, smaller size of DNA and base constituents in the RNA. These are of three types- Methanogens (methane producing, cause explosion in coal mines), Halophiles (live in extreme saline conditions, contain purple pigment bacteriorhodopsin for ATP synthesis from sunlight) and Thermophiles or Thermoacidophiles (withstand high temperature and acidity, mostly grow in hot sulphur springs).

Eubacteria are the true bacteria. They are prokaryotic which means they do not have a nucleus. They lack mitochondria. They are unicellular. Eubacteria can survive in a wide range of environments. They have a rigid cell wall made up of peptidoglycan. Some of the eubacteria are aerobic which means they need oxygen to survive, while some others are (anaerobic) while some others depend on other organisms for their food (heterootrophic) Eubacteria move with the help of flagella or cilia. Bacteria usually reproduce asexually (by themselves) through the process of binary fission. All eubacteria are either spirilla (spiral shaped), bacilli (rod shaped), or cocci (spherical). We use Eubacteria to produce drugs, wine, and cheese.
Examples of eubacteria include Escherichia coli, Clostridium tetani, Streptococcus pneumoniae etc.