The document summarizes different systems of classification of microorganisms over time, from Linnaeus' two kingdom system to the current three domain system. It explains Carl Woese's three domain system which classifies organisms into Archaea, Bacteria and Eukarya domains based on genetic sequencing and differences in ribosomal RNA. The five kingdom system of Monera, Protista, Fungi, Plantae and Animalia is also described. Examples are provided of key microorganisms classified under each system.

1. Classification of Microorganisms
Course: B.Sc. Microbiology
Sem II
Sub: Bacteriology
Unit I

2. Types of Classification Systems cont.
• Carlolus Linnaeus proposed the Two Kingdom
Classification in 1758.
• The two kingdoms consisted of:
– Plantae
– Animalia

3. 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.

4. 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

5. 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

6. 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
1

7. • 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

8. Protista
Paramecium diatom
amoeba euglena
2 3
4
5

9. 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)

10. 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

11. • MAJOR GROUPS OF MONERA:
1. Archaebacteria: Methanogens,
Halophyles, thermoacidophyles
2. Eubacteria: Vibrio, mycobacteria
3. Cyanobacteria: Nostoc, Anabena
1
1
HalobacteriumVibrioAnabenaNostoc
6 7 8 9

12. 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

13. • 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)

14. 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.

15. 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.

16. 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

17. References
Books:
1. Biology of microorganisms By M. T. Madigan, J. M. Martinko, D. A.
Stahl and D. P. Clark
Images:
1. https://lh4.ggpht.com/BL8zyuw37iAzWft6GzMuHTWQ7LmX1pGCKxaXjY_wF8R
uMzVbHGnNAsu-XFO-r6w_ozc8hHM=s125
2. http://cfb.unh.edu/phycokey/Choices/Amoebae_Flagellates_Ciliates/Ciliates/P
ARAMECIUM/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/A
nabaena9c.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