Download Classification

Second Lecture
Bacterial Taxonomy
and Classification
Taxonomy: The science of classification of living
organisms. It consists of THREE areas:
1. Classification
2. Nomenclature
3. Identification
Classification
Arrangement into taxonomic groups (taxa):
Kingdoms or domains, divisions or phyla,
classes, orders, families, genera and species.
Nomenclature: Giving international names to taxa
Identification: Known or unidentified species?
( to speciate). The process is called phenotyping.
Microbial Classification
- Binomial system of nomenclature (18th century):
First: Genus (pl. genera), first letter capital,
underline or italicize, e.g., Shigella, or Shigella;
genus named also by a single letter ( Shigella = S)
Second: Specific epithet; first letter small,
underline or italicize (e.g. Shigella dysenteriae, or
Shigella dysenteriae; if a single species: “sp.”,
more than one species: “spp.” e.g. Shigella spp.
Other information about nomenclature
- First name + second name = species
- Sub-specific epithet = ssp., e.g., H. influenza ssp.
aegyptius
- Nickname: e.g. Staphylococcus = Staph.
- Bacterial names are named for the disease, e.g. Vibrio cholerae = cholera
Classifications of living organisms
1. FIVE Kingdoms (see names)
2. Three-Domain System- based on rRNA
differences (by Carl Woese, 1970s):
A. TWO domains prokaryotes
(Archaea and Bacteria)
B. ONE domain Eucarya or Eukarya
Ribosomal RNA (rRNA)
- rRNA sequencing
- rRNA has 2 subunits:
1. Small subunit rRNS (SSUrRNA), ONE RNA:
a. Bacteria : 16S; coding gene contains 1500 DNA
nucleotides (16S rDNA sequence)*
b. Eukaryotes: 18S; coding gene contains 2000
nucleotides (18S rDNA sequences)*
* Similarities & differences based on rDNA sequences
2. Large subunit rRNA (LSUrRNA)
NOTE: ANSWER ALL THE
10 MCQ QUESTIONS IN
YOUR BOOK (BURTON’S
MICROBIOLOGY for the
HEALTH SCIENCES, Tenth
Edition)
- Good Luck -
Microscopes
Learning objective
1. Learn and understand the interrelationship
between the different of measures of the
METRIC system.
2. Learn the sizes of different organisms.
3. Compare the characteristics and capabilities
of the different types of microscopes.
4. Answer correctly (exercise) the 10 MCQ
about microscopy of your Burton’s textbook
Types of Microscopes
1. Simple
2. Compound light (Bright-field)
3. Dark-field
4. Phase contrast
5. Fluorescence
6. TEM
7. SEM
8. Atomic Force Microscope (AFM)
Microscopes
1. Simple microscope:
- Anton van Leeuwenhoek
- ONE lens
- Magnification X 3-20
2. Compound microscope (objective lens):
- Hans Jansen & Son Zakarias
- Low power X4 X10 (eye piece) = 40
- Medium
X10 X 10 = 100
- High
X40 X 10 = 400
- Oil-immersion X100 X 10 = 1000
Cont./… Microscopes
2. Compound microscope (objective lens):
- Hans Jansen & Son Zakarias
Microbes
* Very tiny (small)
* Require microscope to see them
* Size & volume: Metric
- Micrometer “µm” (10-6 meter) = Micron (µ)
- Nanometer “nm” (10-9 meter) = Millimicron (mµ)
* Microbes : - Coccus (spherical) = 1 µm
- Bacillus (rod) = 3 µm long
- Viruses = 0.01-0.3 µm
- Fungi = 2 - 30 µm
- Parasites = 5- 2000 µm
Electron Microscopes (EM):
1. Transmission (TEM)
- X 1 Million
- Internal microbial features’ examination
- Killed microbes
2. Scanning (SEM)
- Less magnification than TEM
- Surface examination of microbes
- Killed microbes
Atomic Force Microscopes:
- Living organisms
Microscopy
1. Sizes (see Table 2-1):
bacteria: Micrometers (µm)
Viruses : Nanometers
2. Total magnification= Objective X Ocular
3. Background of microscopy bright or dark
in bright-field and dark-field microscopes
respectively
cont./…
Cont./microscopy
4. Images’ (photographs’) names:
- Compound light: Photomicrograph
- TEM: Transmission electron micrographs
- SEM: Scanning electron micrographs
5. Ocular lens (eye piece)
- X10
- Monocular
- Binocular
- Multi-Head (Teaching) ± Screen
Resolving (resolution ) power
Is the ability of an optical instrument to
distinguish between two adjacent objects.
Examples:
- Human eye = 0.2 mm
- Compound light microscope = 0.2 µm
- TEM = 0.2 nm
- SEM = 20 nm (X100-200 < TEM)