LECTURE NOTE ON CLASSIFICATION OF MICROORGANISMS.pptx

This section provides an overview of microbial classification and this will also enhance the students knowledge regarding difference categories of microorganisms

1. CLASSIFICATION OF MICROORGANISMS ABURA GEOFFREY

2. Introduction Classification is the act of forming into groups or categories according to some common relations or attributes or similarities. The science of classification of living forms is called taxonomy (from the Greek for orderly arrangement). There may be as many as 100 million different living organisms, but fewer than 10% have been discovered, much less classified and identified In 2001, an international project called the All Species Inventory was launched whose purpose was to identify and record every species of life on Earth in the next 25 years. Whereas biologists have identified more than 1.7 million different organisms thus far, it is estimated that the number of living species ranges from 10 to 100 million

3. Con’t 1735 - Carolus Linnaeus: introduced formal classification system dividing living organisms into 2 kingdoms: Plantae & Animalia 1857 - Carl von Nageli : proposed bacteria & fungi be placed in the plant kingdom. 1937 - Edouard Chatton : introduced the term prokaryote (distinguish cells having no nucleus from the nucleated cells of plants and animals) 1969 - Robert H. Whittaker: founded the five-kingdom system 1978 - Carl R. Woese : proposed elevating the three cell types to a level above kingdom, called domain and these are: Eubacteria, Archaea , Eukarya Eubacteria ; true bacteria, peptidoglycan Archae ; o dd bacteria that live in extreme environments, high salt, heat, etc. (usually called extremophiles) Eukarya : have a nucleus & organelles (humans, animals, plants)

4. The illustration below shows the classification of microorganisms

5. Con’t 1. Virus: Viruses have a very simple structure and are the smallest microorganism discovered so far by man. They can reproduce and don’t breathe at all. Viruses can capture living cells and reproduce on them. 2. Viroids: A viroid is an infectious agent of plants similar to a virus but smaller than any of the known viruses, consisting of only a short, single strand of RNA without a protein coat. It is not clear whether  viroids  occur in animal cells, lacking the protein coat of a virus.

6. Con’t 3. Prions: Prions are infectious particles that contain no nucleic acids which causes disease of the brain and other neural tissue. 4. Algae: Algae also cannot be seen with the naked eyes. There are unicellular algae as well as multicellular filamentous algae. They produce their own food by photosynthesis , hence they can be known as Autotrophic. Most forms of algae are aquatic so they are living in fresh water and in sea water too. Algae develop as clusters of cells and as individual cells.

7. Con’t 5. Protozoa: Protozoa is also a unicellular organism with large number of aquatic species of around 40,000. Usually they move onto other living organisms and feed on them. Protozoa has a body size of 10-52 ͷ m. 6. Fungi: Fungi are non- green plants which are not photosynthetic. They are heterotrophic nutrition type because they are parasitic or saprophytic. They show a symbiotic relationship with Algae to form lichens. Some fungi can be seen with naked eyes. F ungi such as mushrooms and molds have a multicellular structure known as mycelium.

8. Symbiosis Some fungi e.g. form symbiotic relationships with other organisms. A lichen is an organism which is a combination of a fungus and an alga Mutualistic relationship in which each partner benefits. Alga : Provides nutrients by photosynthesis to fungus. Fungus : Provides attachment and protection from desiccation. Grow very slowly, secreting acids that break down rocks