Question

What was the basis of classification for archaea and eubacteria in the six kingdom classification?

Answer 1

Six kingdom classification:

1. Six kingdom classification was given by Carl Woese.
2. These six kingdoms are Kingdom Archaebacteria, Kingdom Eubacteria, Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and Kingdom Animalia.
3. Woese discovered that the six natural kingdoms were divided into three main categories which are the domains archaea, bacteria, and eukarya.

He separated eubacteria and archebacteria on the basis of:

1. The nucleotide sequence of 16s rRNA.
2. Lipid structure in the cell membrane.
3. Eubacteria have a sensitivity to antibiotics, while archaebacteria are not susceptible to antibiotics.

Archaebacteria and eubacteria can be classified under different classes based on the following differences

	ARCHAEBACTERIA	EUBACTERIA
CELL WALL	The cell wall is composed of pseudopeptidoglycan.	The cell wall is made of muramic acid/lipopolysaccharides with peptidoglycan.
MODE OF REPRODUCTION	The archaea perform asexual reproduction.	The eubacteria reproduce through sexual as well as asexual reproduction.
PATHOGENICITY	They are non-pathogenic.	Eubacteria are generally pathogenic.
METABOLISM	Archae can use hydrogen, oxygen, methane, carbon dioxide, hydrogen sulfide, sulfur, and some species can also use ammonia.	Eubacteria can be classified as : Aerobes ( use oxygen) Anaerobes ( do not use oxygen)
NUTRITION	Archae can be of different types: Phototrophs ( use sunlight) Lithotrophs (use inorganic compounds) Organotrophs (relies on organic compounds)	Chemosynthesis, photosynthesis, or absorption.
HABITAT	Archae can live in extreme conditions like hot springs, geothermal vent, ocean depth, etc.	They are found in air, water, soil, and on or in other animals.
LINKAGE IN CELL WALL	The lipids in the cell wall have the hydrocarbon chains attached by ether linkages to the glycerol molecule.	The glycerol is attached to the hydrocarbon chains by ester linkages.
rRNA	ribosomal RNA has 16S rRNA, 23S, and 5S rRNAs intricated with 60-70 ribosomal proteins.	16s, 23s, and 5s are transcribed together to make a single rRNA molecule.
ORGANISM	Methanogens, halophiles, thermophiles, and psychrophiles	Bacteria, cynobacteria.