Download Naming and classifying microorganisms

Naming and
classifying
microorganisms
lecture 3
General microbiology 231
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Dr. Samah Noor
• Naming Microorganisms (Binomial nomenclature)
was established by Carolus LInnaeus- in 1735
• Purpose: provide a means of international reference
• Each organism was assigned a Latin or Latinized
genus name (capitalized) and specific epithet (species)
(follows and not capitalized)
• Even when derived from a proper noun such as the
name of a person or place, both parts are italicized.
• Thus the binomial name of the e. coli is now written as
E. coli
• Latin was used because it was the language used by
scholars
General microbiology 231
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Dr. Samah Noor
naming microbes
• Taxonomy: is the science of classification and systematic
arrangement of organisms into groups-taxa
• Microbial systematics: is classifying, naming, and
identifying
• Taxonomy orderly arrangement of units into groups of
larger groups of increasing inclusiveness
• Nomenclature: naming of units characterized and
delineated by classification
• Objective: group organisms so as to reflect similarities and
differences
General microbiology 231
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Dr. Samah Noor
naming microbes
• Binomial nomenclature is now governed by various
internationally agreed codes of rules,
• Rules for naming protozoa and parasitic worms are in the
International Code of Zoological Nomenclature.
• Rules for naming fungi and algae are in the International Code of
Botanica Nomenclature.
• Rules for naming newly classified bacteria are established by the
International Committee ON Systematics Of Prokaryocytes and
published in the International Bacteriological Code.
• They are then included in the standard of reference for bacteria,
Bergey’s Manual of Systematic Bacteriology.
•
General microbiology 231
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Dr. Samah Noor
naming microbes
• New laboratory techniques, involving analysis of DNA
and RNA, have caused some bacteria to be reclassified.
• Sometimes organisms which have been in separate
genera are combined into one genus; other times
organisms previously in the same genus are split out
into separate genera.
• Even if the genus name is changed, the species name
usually remains the same.
General microbiology 231
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Dr. Samah Noor
TAXONOMIC
HIERARCHY
• This is the complete list of taxa (classification groups)
which are used to classify living organisms:
Domain (this is the relatively new one)
Kingdom
Phylum
Division (this one may be used in place of phylum in botany)
Class
Order
Family
Genus
Species
General microbiology 231
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Dr. Samah Noor
CLASSIFICATION OF
PROKARYOCYTES
•
Bergey’s Manual, the standard for classification of prokarocytes.
•
Two domains, Bacteria and Archaea, are included.
• The taxon Kingdom is not used, so then each domain is divided into phyla, based
on similarities in rRNA.
• Organisms continue to be divided into taxa that are more and more specific until,
eventually reaching the species level.
• In eukaryocytes, a species is defined as a group of closely related organisms that
breed among themselves. A bacterial species is defined as a population of cells
with similar characteristics.
• Members of the species are VERY similar to each other, but all may not be totally
identical.
• Strains are identified by numbers, letters, or names that follow the species name.
General microbiology 231
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Dr. Samah Noor
CLASSIFICATION OF
EUKARYOCYTES
DOMAIN: EUKARYA---contains 4 kingdoms
•
KINGDOM: PROTISTA---unicellular eukaryocytes
except yeasts & molds
•
KINGDOM: FUNGI---unicellular yeasts, multicellular
molds, macroscopic fungi--these all absorb organic matter
through their plasma membranes
•
KINGDOM: PLANTAE---plants--macroscopic algae,
flowering plants--all are multicellular, all carry on
photosynthesis
•
KINGDOM: ANIMALIA---animals--sponges, worms,
insects, vertebrates--all ingest nutrients
General microbiology 231
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Dr. Samah Noor
CLASSIFICATION OF
VIRUSES
•
Virus classification is a mess.
•
Viruses are not composed of cells, so there are arguments about whether they are even really alive.
•
Alive: They have either DNA or RNA, which must mean they are living
•
Not alive: No cellular structure
•
No metabolism and no reproduction until they invade a living cell
•
Do not have DNA and RNA both—living things have both
•
Viruses are described as obligate intracellular parasites.
•
A viral species is a population of viruses with similar characteristics that occupies a particular ecological niche. (The
ecological niche of a virus is its host cell). There are two hypotheses on the origin of viruses:
1. They arose from strands of DNA similar to plasmids
2. They developed from degenerative cells that lost their ability to function independently
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Dr. Samah Noor