Classification of microorganisms

Classification of microorganisms, Five kingdom concept, Eight kingdom concept, Three domain system

1. CLASSIFICATION OF MICROORGANISMS R. NITHYA M. Sc., M. Phil ., (Ph. D) ASSISTANT PROFESSOR IN BIOTECHNOLOGY SRI ADI CHUNCAHNAGIRI WOMEN’S COLLEGE, CUMBUM, THENI DT, TAMILNADU, INDIA

2. MICROORGANISMS Microorganisms or microbes are organisms invisible to naked eye and are visible under a microscope. Based on their unique features, they are divided into certain groups. They include Bacteria Viruses Algae Fungi Protozoa

3. MICROBIAL TAXONOMY The classification of microorganisms The microorganisms are classified in the following ways Based on plants and animals Based on cellularity Based on the types of nuclear materials Five kingdom concept Eight kingdom concept Three domain system

4. CLASSIFICATION OF MICROBES BASED ON PLANTS OR ANIMALS Aristotle classified the living organisms into two kingdoms KINGDOM Plantae Animalia Algae Fungi Bacteria All animals Protozoa

5. CLASSIFICATION BASED ON CELLULARITY Based on cellularity , microbes are classified into three categories Cellularity Non-cellular Unicellular Multicellular Microbes have no cells E.g. Viruses Microbes have single cells E.g. Protozoa Bacteria Some Algae Some Fungi Many cells E.g. Fungi Algae etc.

6. CLASSIFICATION BASED ON THE NATURE OF NUCLEAR MATERIALS Nuclear Materials Prokaryotes Eukaryotes Organisms do not contain nucleus Nuclear materials not surrounded by nuclear membrane E.g . Bacteria True nucleus Nuclear materials not surrounded by nuclear membrane E.g. Protozoa Algae Fungi All animals

7. FIVE KINGDOM CONCEPT Whittaker (1969) proposed a five kingdom concept for the classification of microbes

8. Classification based on mode of nutrition and cellular organization

9. EIGHT KINGDOM CONCEPT This concept was proposed by Cavalier-Smith in 1987 Eight Kingdom Concept Empire Bacteria Empire Eukaryota Kingdom Eubacteria Archeobacteria Kingdom Archezoa Protozoa Chromista Plantae Fungi Animalia

10. EIGHT KINGDOM

11. Empire – Bacteria Eukaryota – Includes all true bacteria Archeobacteria – All filamentous bacteria Empire – Eubacteria Archezoa – Microscopic animals feeding on archebacteria Protozoa – Unicellular animals Chromista – Photosynthetic organisms – Diatoms, cryptomonads and brown algae Plantae – All Photosynthetic plants and algae Fungi – Eukaryotic multicellular organisms – absorptive mode of nutrition Animalia – Multicellular animals – ingestive mode of nutrition

12. THREE DOMAIN SYSTEM Proposed by Carl Woese , Otto Kandler and Wheelis in 1990 Phylogenetic system. Based on differences of nucleotides in cell’s ribosomal RNAs as well as the cells’ membrane lipid structure and its sensitivity to antibiotics. Three domaims are Bacteria Archea Eukaryota Carl Woese Otto Kandler

13. Domain – Bacteria Unicellular or filamentous prokaryotes They have diacyl glycerol diester and eukaryotic type of rRNAs in the cells. Domain – Archea Organisms having isopyrenoid glycerol diester in cell membrane Archebacterial rRNAs in cells. Domain – Eukaryota Glycerol fatty acyldiester in cell membrane Eukaryotic rRNAs in the cells

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