THREE DOMAINS OF LIFE-[BP211525].pptx

About kingdom classification of Microorganisms,

1. THREE DOMAINS OF LIFE By: K.sanjay , I M Sc Microbiology[BP211525], Sacred Heart College[Autonomous], Tirupattur . To: Dr.P.Saran Raj, Head of D epartment of Microbiology, Sacred Heart College[Autonomous], Tirupattur .

2. Discovered by: The term “Domain” was introduced by American Microbiologist and biophysicst carl woese et al [1990] together with the proposal of a natural classification system for all life on earth ,including microorganisms, which had previously escaped any attempt of classification based on evolutionary relationships.

3. Organisms can be classified into one of three domains based on differences in the sequences of nucleotides in the cell's ribosomal RNAs ( rRNA ), the cell's membrane lipid structure, and  its sensitivity to antibiotics . The three domains are the Archaea , the Bacteria, and the Eukarya . Three Domains of Life:

4. Archaea are prokaryota cells, typically characterized by membrane lipids that are branched  hydrocarbon  chains attached to glycerol by ether linkages. The presence of these ether linkages in Archaea adds to their ability to withstand extreme temperatures and highly  acidic  conditions, but many archaea live in mild environments.  Halophiles , organisms that thrive in highly salty environments, and  hyperthermophiles , organisms that thrive in extremely hot environments, are examples of Archaea . [1] Archaea evolved many cell sizes, but all are relatively small. Their size ranges from 0.1  μm to 15  μm diameter and up to 200  μm long. They are about the size of bacteria, or similar in size to the  mitochondria  found in eukaryotic cells. Members of the genus  Thermoplasma  are the smallest of the Archaea Archaea :

5. Even though bacteria are prokaryotic cells just like Archaea , their membranes are made of phospholipid bilayers.  Cyanobacteria  and  mycoplasmas  are two examples of bacteria. They characteristically do not have ether linkages like Archaea , and they are grouped into a different category—and hence a different domain. There is a great deal of diversity in this domain. Confounded by that diversity and  horizontal gene transfer , it is next to impossible to determine how many species of bacteria exist on the planet, or to organize them in a tree-structure, without cross-connections between branches . Bacteria:

6. Members of the domain Eukarya —called eukaryotes—have membrane-bound organelles (including a nucleus containing genetic material) and are represented by five  kingdoms :  Plantae ,  Protozoa ,  Animalia ,  Chromista , and  Fungi . Eukarya :