Classification of Microorganisms

Course: B.Sc. MicrobiologySem II

Sub: BacteriologyUnit I

Types of Classification Systems cont.

• Carlolus Linnaeus proposed the Two Kingdom Classification in 1758.

• The two kingdoms consisted of:– Plantae– Animalia

THREE KINGDOM SYSTEM• ERNEST HAECKEL 1866‐• KINGDOM PROTISTA: – It includes unicellular & colonial eukaryotes such as

bacteria, algae, fungi & protozoans.• KINGDOM PLANTAE: – It includes multicellular photosynthetic plants.

• KINGDOM ANIMALIA: – It includes multicellular animals.

Types of Classification Systems cont.

• The next classification system that came about consisted of 5 kingdoms.

• It was proposed by Robert Whittaker in 1969.• The 5 kingdoms consisted of:– Plantae– Animalia– Fungi– Protista– Monera

Robert Whittaker’s Five Kingdom System

• Plantae– Plants are immobile, multicellular eukaryotes that produce

their food by photosynthesis and have cells encased in cellulose cell walls.

– Examples: Ferns, pine trees, roses• Animailia– Animals are multicellular, heterotrophic eukaryotes that

are capable of mobility at some stage during their lives, and that have cells lacking cell walls.

– Examples: Humans, worms, spiders

Robert Whittaker’s Five Kingdom System• Fungi

– Fungi are a eukaryotic, heterotrophic, usually multicellular group having multinucleated cells enclosed in cells with cell walls.

– They obtain their energy by decomposing dead and dying organisms and absorbing their nutrients from those organisms.

– Examples: Mushrooms, moulds, yeast

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• Protista• The most ancient eukaryotic kingdom, protista include a variety of

eukaryotic forms. • Perhaps they are best defined as eukaryotes that are not fungi, animals, or

plants.• Cell wall is usually absent, if present it is impregnated with silica (diatoms).• Photosynthetic or non photosynthetic.• Locomotory structure may be cilia, flagella, pseudopodia or absent.• Examples: Paramecium, amoeba, diatom, euglena, some algae

(unicellular), slime moulds

Robert Whittaker’s Five Kingdom System

Protista

Paramecium diatom

amoeba euglena

2 3

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Robert Whittaker’s Five Kingdom System

• Monera– Monera are the only kingdom composed of prokaryotic

organisms, they have a cell wall, and lack both membrane-bound organelles and multicellular forms.

– Examples: Bacteria, blue-green bacteria (cyanobacteria)

Characteristics of Monera:• Unicellular or filamentous prokaryotes• Omni present (air, soil, hot springs, deserts, deep sea, snow & as

parasites)• Cell wall is composed of polysaccharides & amino acids(peptido

glycons ormurein)• Autotrophic (photo & chemosynthetic) & heterotrophic

(saprophytic & parasitic)• Reproduce by vegetative, asexual & sexual methods

• MAJOR GROUPS OF MONERA:1. Archaebacteria: Methanogens,

Halophyles, thermoacidophyles2. Eubacteria: Vibrio, mycobacteria3. Cyanobacteria: Nostoc, Anabena

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HalobacteriumVibrioAnabenaNostoc6 7 8 9

Types of Classification Systems cont..

• In the 1970’s, microbiologist Carl Woese, among other researchers conducted studies and concluded that a group of prokaryotic microorganisms called archaebacteria are separate from other monerans.

• Therefore, they decided to split kingdom monera into two separate kingdoms:– Eubacteria– Archaebacteria

• Archaebacteria– Unicellular– Prokaryotic– Exist in extreme environments – they do not need oxygen or

light to live– Examples: methanogens, extreme thermophiles, extreme

halophiles

• Eubacteria– Unicellular– Prokaryotic– Heterotrophic, autotrophic, and chemotrophic– Examples: Bacteria, cyanobacteria (blue-green bacteria)

Three Domain System• The Three Domain System, developed by Carl Woese,

is a system for classifying biological organisms. • Over the years, scientists have developed several

systems for the classification of organisms. • From the late 1960's, organisms had been classified

according to a Five Kingdom system. • This classification system model was based on

principles developed by Swedish scientist Carolus Linnaeus, whose hierarchical system groups organisms based on common physical characteristics.

The Three Domain System• As scientists learn more about organisms, classification systems change. • Genetic sequencing has given researchers a whole new way of analyzing

relationships between organisms.• The current system, the Three Domain System, groups organisms primarily based

on differences in ribosomal RNA structure. • Ribosomal RNA is a molecular building block for ribosomes.• Under this system, organisms are classified into three domains and six kingdoms. • The domains are Archaea, Bacteria, and Eukarya. The kingdoms are Archaebacteria

(ancient bacteria), Eubacteria (true bacteria), Protista, Fungi, Plantae, and Animalia.

• The Archaea and Bacteria domains contain prokaryotic organisms. These are organisms that do not have a membrane bound nucleus.

• Eubacteria are classified under the Bacteria domain and archaebacteria are classified as Archaeans.

• The Eukarya domain includes eukaryotes, or organisms that have a membrane bound nucleus. This domain is further subdivided into the kingdoms Protista, Fungi, Plantae, and Animalia.

Comparison of Classification Systems• Five Kingdom System

Kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.

Three Domain System • Archaea Domain

– Archaebacteria Kingdom• Bacteria Domain

– Eubacteria Kingdom• Eukarya Domain

– Protista Kingdom– Fungi Kingdom– Plantae Kingdom– Animalia Kingdom

References

Books:1. Biology of microorganisms By M. T. Madigan, J. M. Martinko, D. A. Stahl and D. P.

ClarkImages:1. https://lh4.ggpht.com/

BL8zyuw37iAzWft6GzMuHTWQ7LmX1pGCKxaXjY_wF8RuMzVbHGnNAsu-XFO-r6w_ozc8hHM=s125

2. http://cfb.unh.edu/phycokey/Choices/Amoebae_Flagellates_Ciliates/Ciliates/PARAMECIUM/Paramecium_05_600x395_caudatum.jpg

3. http://www.bodc.ac.uk/projects/uk/mfmb/introduction/images/diatoms.jpg 4. http://www.microscopy-uk.org.uk/mag/imgsep01/amoebaproteus450.jpg 5. https://lh6.ggpht.com/mkGhpDrT154r8rgB0tTM4wfgOG0-

ULTlnUzmbRT7pvKbgVUoTrBC9XuJEqxTdQkEniP1jQ=s170 6. http://www.ohio.edu/plantbio/vislab/algaeimage/jpegs/nost1nitr.JPG 7. http://protist.i.hosei.ac.jp/PDB/images/Prokaryotes/Nostocaceae/Anabaena/

Anabaena9c.jpg 8. https://s3.amazonaws.com/healthtap-public/ht-staging/user_answer/

reference_image/8742/large/Cholera.jpeg?1344948822 9. http://plantphys.info/organismal/lechtml/images/halobacterium.jpg