II. Classification of Microorganisms
A.
B.
C.
D.
Principles of Classification and
Nomenclature
Eukaryotic Organisms
Prokaryotic Organisms
Viruses
II. A. Principles of Classification
and Nomenclature
• Taxonomy
– Kingdom
– Phylum (pl: Phyla)
– Class
– Order
– Family
– Genus (pl: Genera)
– Species (pl: Species)
II. A. Principles of Classification
and Nomenclature
• Phylogenetic vs. Phenetic Classification
Systems
– Phylogenetic Classification System: Groups
reflect genetic similarity and evolutionary
relatedness
– Phenetic Classification System: Groups do
not necessarily reflect genetic similarity or
evolutionary relatedness. Instead, groups are
based on convenient or observable
characteristics.
II. A. Principles of Classification
and Nomenclature
• Definition of “species” in microbiology
– Type strains:
“Known” well-characterized pure
cultures; references for the
identification of unknowns
– American Type Culture Collection
(ATCC)
II. A. Principles of Classification
and Nomenclature
• “Species” vs. “Strain”
– Species: A specific or defined type of
organism, defined by similarity with
known species.
– Strain: Genetic variation within a
species
II. A. Principles of Classification
and Nomenclature
• Nomenclature
– Scientific name (Systematic Name)
Binomial System of Nomenclature
Genus name + species name
italicized or underlined
genus name is capitalized and may be
abbreviated
species name is never abbreviated.
eg: Bacillus subtilis
B. subtilis
II. A. Principles of Classification
and Nomenclature
• Nomenclature (cont.)
– Common or descriptive names
(trivial names)
eg: tubercle bacillus
(Mycobacterium tuberculosis)
meningococcus
(Neiserria meningitidis)
Group A streptococcus
(Streptococcus pyogenes)
II. B. Eukaryotic Organisms
• Eukaryotic Cells
Have:
Complex Internal Membrane System
Compartmentalization
Membrane-Enclosed Organelles
DNA is enclosed in a membrane-bound
nucleus
Includes:
Animal & Plant cells
Eukaryotic Microorganisms
II. B. Eukaryotic Organisms
• Eukaryotic Kingdoms
– Kingdom Protista
(Protozoa and Algae)
– Kingdom Fungi
– Kingdom Plantae
– Kingdom Animalia
II. C. Prokaryotic Organisms
• Prokaryotic Cells
– Have: No (or few) internal membranes
– Many processes that are associated with
organelles in eukaryotes (eg. respiration,
photosynthesis) are mediated by specialized
regions of the plasma membrane in
prokaryotes
II. C. Prokaryotic Organisms
• Prokaryotic Cells (cont.)
– There is no membrane-bound nucleus in
prokaryotes. Instead the DNA is located
within a specialized region of the cytoplasm
of the cell called the nucleoid region. There
is no nuclear membrane surrounding the
nucleoid.
– Includes: The Bacteria
The terms “prokaryotic cell” and “bacterial
cell” often are used interchangeably
II. C. Prokaryotic Organisms
• Prokaryotic Kingdoms
– Kingdom Eubacteria
– Kingdom Archaeobacteria
II. D. Viruses
• Structure of a “Virus Particle”
– Noncellular Biological Entity
– Contains either DNA or RNA (not both)
– Nucleic Acid is surrounded or coated by a
protein shell (capsid)
– Some viruses possess a membrane-like
envelope surrounding the particle
II. D. Viruses
• Viral Replication
– No independent metabolism or replication
– Replicate only inside an infected host cell
– Do not replicate via a process of cell division
– Replicate via a process of:
• Attachment and Penetration
• Disassembly (uncoating)
• Synthesis of Viral Protein and Nucleic Acid
• Reassembly of new viral particles
• Release of new viral particles