Classification and Nomenclature of Micro organisms

1. Classification and
Nomenclature of
Microorganisms
By
Dr Asma Firdous

2. Introduction
Taxonomy:
Taxonomy is the classification, nomenclature and identification of
microbes (algae, protozoa, slime moulds, fungi, bacteria, archaea and
viruses). The naming of organisms by genus and species is governed
by an international code

3. 1. Classification: It refers to the hierarchy based arrangement of bacteria into taxonomic
groups or taxa (singular, taxon) on the basis of similarities or differences in their
biochemical, physiological, genetic, and morphological properties.
2. Nomenclature: It refers to the naming of taxa according to their characteristics, by
following the international rules.
3. Identification: It refers to the practical use of a classification scheme such as: (1)
Identification of an unknown taxon by comparing with a defined and named taxon, (2)
To isolate and identify the causative agent of a disease.

4. Taxonomy is important for several reasons
1. It allows us to organize huge amounts of knowledge about
organisms
2. Allows us to make predictions and frame hypotheses for further
research based on knowledge of similar organisms.
3. It places microorganisms in meaningful, useful groups with
precise names so that microbiologists can work with them and
communicate efficiently.
4. Identification of microorganisms accurately

5. The Greek philosopher Aristotle
attempted to classify all living
things as either Plant or Animal.
• Land Dwellers
• Water Dwellers
• Air Dwellers
Origin of the Names

6. The efforts to classify living things
saw great progress in the work of
Carl Linnaeus, a Swedish botanist.
He developed his naming system in
the middle 1700’s, which is
essentially the same one we use
today.

7. • Name all known plants, animals,
and minerals using Latin and
Greek names.
• One of his books, Systema
Naturae, meaning “The Natural
Classification", was published in
1735 and was based on his
religious belief that one could
understand God by studying his
creation.

8. Today, microorganism names originate from four different sources:
• Descriptive – For example Staphylococcus aureus (grape-like cluster of
spheres, golden in color).
• Scientist’s names – e.g., Escherichia coli (Theodor Esherich), Erlichia
(Paul Erlich), Nessieria (Albert Neisser), Listeria (Joseph Lister).
• Geographic places – e.g., Legionella longbeachiae (Long Beach,
California), Pasturella tularensis (Tulare County, California),
Pseudomonas fairmontensis (Fairmount Park, Pennsylvania).
• Organizations – e.g., Legionella (American Legion), Afipia felis (Air
Force Institute of Pathology), Cedecea spp. (Centers for Disease
Control), Bilophila wadsworthia (VA Wadsworth Medical Center in Los
Angeles)

9. A Swedish naturalist named Carolus Linnaeus is considered the
'Father of Taxonomy‘ since 1700s
His two most important contributions to taxonomy were:
•A hierarchical classification system
•The system of binomial nomenclature
He proposed that there were three broad groups, called
kingdoms, into which the whole of nature could fit.
These kingdoms were animals, plants, and minerals.
Binomial nomenclature meant naming species in 2
words : genus , followed by species
History of Taxonomy

10. The two kingdom classification system was given by Carlous Linaaeus in 1758.
He then divided each kingdom into classes and later grouped the classes into
phyla for animals and divisions for plants.
2 Kingdom Classification

11. He classifies all living organisms into three kingdoms.
• Animalia
• Plantae
• Protista
Haeckel’s Three kingdom Classification system

12. 4 Kingdom Classification
The development of optic and electronic microscopy showed important differences in
cells, mainly according to the presence or absence of distinct nucleus, leading Édouard
Chatton to distinguish organisms in prokaryotes (without a distinct nucleus) and
eukaryotes (with a distinct nucleus) in a paper from 1925.
Based on it, Copeland proposed a four-kingdom system, moving prokaryotic organisms,
bacteria and “blue-green algae”, into the kingdom Monera

13. The position of fungi was not well established, oscillating between
kingdoms Protista and Plantae.
So, in 1969, Robert Whittaker proposed a fifth kingdom to include them,
the called Kingdom Fungi.
5 Kingdom Classification

15. • The three-domain system is a biological classification introduced by Carl Woese in 1977
that divides cellular life forms into archaea, bacteria, and eukaryote domains.
• In particular, it emphasizes the separation of prokaryotes into two groups, originally
called Eubacteria (now Bacteria) and Archaebacteria (now Archaea).
• Woese argued that, on the basis of differences in 16S rRNA genes, these two groups and
the eukaryotes each arose separately from an ancestor with poorly developed genetic
machinery, often called a progenote.
3 Domain Classification

16. 6 Kingdom Classification
Cavalier and Smith’s Classification:
It is a molecular classification, which divides all living structures of the earth into six kingdoms—
Bacteria,
Protozoa, Chromista, Plantae, Fungi and Animalia.
Kingdom Bacteria is divided successively in decreasing order of hierarchy into phylum/division,
class, order,
suborder, family, tribe, genus and species.

17. full taxonomical position of Escherichia coli

18. There is no universally accepted principle to classify
bacteria. There are mainly three approaches:
1.Phylogenetic
2.Adansonian
3.Molecular
Bacteria Classification

19. Phylogenetic Classification
This is a hierarchical classification representing a branching tree-like arrangement; one characteristic (or
trait) is being employed for division at each node of the tree
This system is called phylogenetic because it implies an evolutionary arrangement of species
Here, the characteristics are arbitrarily given special Weightage
The characteristics are:
1. Morphology of bacteria—cocci or bacilli
2. Staining property such as gram-positive and gram-negative
3. Cultural characteristics such as lactose fermenting and non-lactose fermenting colonies
4. Biochemical reactions, e.g. coagulase positive Staphylococcus and coagulase negative
Staphylococcus
5. Antigenic structure, e.g. antigenic structure of somatic antigen present in bacterial cell wall.

20. Adansonian Classification
To avoid the use of weighted characteristics, Michel Adanson proposed
another method (1774) that classifies
organisms based on giving equal weight to every character of the organism.
This is also called phenetic classification.
• Numerical taxonomy: The concept was first developed by Robert R Sokal and Peter
HA Sneath in 1963
• With the advent of computer facilities, the principle of phenetic classification has been
extended further so that very large numbers of characters of several organisms can
be compared at the same time
• They have created a taxonomic system by using numeric algorithms like cluster analysis
rather than using subjective evaluation of their properties which are arbitrarily given
special weightage.

21. Molecular Classification
It is based on the degree of genetic relatedness of
different
organisms. Guanine + cytosine (G + C) content of
bacteria is
estimated after extracting DNA from pure bacterial
culture.
The nucleotide base composition and the base ratio vary
widely among different groups of microorganisms, but for
any one particular species, it is constant.

22. Nomenclature
It is the branch of taxonomy, that is concerned
with designating scientific names to taxa,
based on a particular classification scheme
and in accordance with agreed international
rules and conventions.

23. Rules of Nomenclature
Use Binary Names: Binary names (invented by
Linnaeus), consisting of a generic name and a species
epithet (e.g., Escherichia coli), must be used for all
microorganisms. Names of categories at or above the
genus level may be used alone, but species and
subspecies names (species names) may not. In other
words…never use a species name alone.

24. Rules of Nomenclature
When to Capitalize – The genus name (and above) is always
capitalized, the species name is never capitalized, e.g. Bacillus
anthracis.
When to Italicize - Names of all taxa (kingdoms, phyla, classes,
orders, families, genera, species, and subspecies) are printed in italics
and should be underlined if handwritten; strain designations and
numbers are not. If all the surrounding text is italic, then the binary
name would be non-italic (Roman typeface) or underlined (e.g. A
common cause of diarrhea is E. coli 0157, a gram negative bacillus).

25. Rules of Nomenclature
When to use Initials A specific epithet must be preceded
by a generic name, written out in full the first time it is
used in a paper. Thereafter, the generic name should be
abbreviated to the initial capital letter (e.g., E. coli),
provided there can be no confusion with other genera
used in the paper. Be careful with the “S” words;
Salmonella, Shigella, Serratia, Staphylococcus,
Streptococcus, etc.

26. Rules of Nomenclature
Common Names - Vernacular (common) names should be in
lowercase roman type, non-italic (e.g., streptococcus, brucella).
However when referring to the actual genus name (or above)
always capitalize and italicize.
Subspecies and Serovars - For Salmonella, genus, species, and
subspecies names should be rendered in standard form:
Salmonella enterica at first use, S. enterica thereafter; Salmonella
enterica subsp. arizonae at first use, S. enterica subsp. arizonae
thereafter.

27. Rules of Nomenclature
• The genus and species are coined based on some property of
the bacteria, e.g.
• Staphylococcus aureus is named after their arrangement in
cluster (Staphyle means bunch of grapes) and type of
pigmentation they produce (aureus meaning golden yellow)
• Neisseria meningitidis is named after—the discoverer (U
Neisser) and the disease it causes (meningitis)
• Brucella suis and Brucella melitensis (named after the
discoverer (Brucella from David Bruce) and the animal host (suis
meaning pig) and the place of discovery (melitensis from Malta,
Europe).

28. Rules of Nomenclature
The recent changes in the taxonomic name of medically
important microorganisms

29. Type Cultures
There are many international reference laboratories which are designated as
type culture reference centers.
• They maintain the representative cultures of the established species, which
show all the standard characteristics of the original strain
• The strains isolated in the laboratories are compared using the standard
strains supplied by these type culture centers
• The original cultures of any new species described are deposited in type
collection centers
• The two most important type collection centers of the world are:
ATCC (American Type Culture Collection), USA
NCTC (National Collection of Type Cultures), UK.