Lecture 2

1. Microbiology
An
introduction
Presented by
D. Mona
Othman
Albureikan
Lectures (3,4)

2. Naming and Classifying Microorganisms
• Carolus Linnaeus : father of Taxonomy
established the system of scientific
nomenclature.
• Each organism has two names: the genus and
species.
• Scientific Names: Are italicized or underlined.
The genus is capitalized, and the species is
lowercase.
• Are “Latinized” and used worldwide.

3. Naming and Classifying Microorganisms
• May be,,,
• describe an organism.
• or honor a scientist.
• identify the habitat of a species.
-Stapllylococcus aureus, a bacterium commonly found
on human skin.
-Staphylo- describes the clustered arrangement of the
cells; coccus indicates that they are shaped like spheres.
- The specific epithet, aureus, is Latin for golden, the
color of many colonies of this bacteria.
- Escherichia coli named for a scientist, Theodor
Escherich , whereas its specific epithet, coli, reminds us
that E. coli live in the colon, or large intestine.

4. Scientific Names
• After the first use, scientific names may be abbreviated
with the first letter of the genus and the specific
epithet:
– Escherichia coli and Staphylococcus aureus are found
in the human body
– E. coli is found in the large intestine, and S. aureus
is on skin.

5. Taxonomy
• The science of classifying
organisms
• Provides universal names for
organisms
• Provides a reference for
identifying organisms
• Taxonomy goal is to show
relationships among organisms.
- Similar species are grouped into a
genus.
- Similar genera are grouped into a
family.
- Families, into an order.
- Orders, into a class.
- Classes, into a phylum.
- Phyla, into a kingdom.
- And kingdoms, into a domain.

7. Phylogenetic Hierarchy
• The study of the evolutionary history of
organisms
• All Species Inventory (2001–2025)
– To identify all species of life on Earth
– Grouping organisms according to
common properties
– Ancestor
– Fossils (bones-shells-or streams that
contain mineral matter-lift imprint on
rock
Organisms is classified in 3 domine system
based on:
1. Cell type
2. Difference in ribosomal RNA(rRNA)
3. Membrane lipid structure
4. Transfer RNA molecules
5. Sensitivity to antibiotics

8. The Three-Domain System.
Archaea
Extreme
halophiles
Methanogens
Hyperthermophile
Eukarya
Animals
Fungi
Ciliates
Dinoflagellates
Diatoms
Euglenozoa
Giardia
Mitochondrion degenerates
Nucleoplasm grows larger
Horizontal gene transfer
occurred within the
community of early cells.
Amebae
Origin of
mitochondria
Origin of chloroplasts
Bacteria
Mitochondria
Cyanobacteria
Chloroplasts
Proteobacteria
Gram-positive
bacteria
Thermotoga

10. The Three Domains

12. Placing Bacteria
1735 Kingdoms Plantae and Animalia
1857 Bacteria and fungi put in the Kingdom Plantae—
“Flora”
1866 Kingdom Protista proposed for bacteria, protozoa,
algae, and fungi
1937 Prokaryote introduced for cells “without a
nucleus”
1961 Prokaryote defined as cell in which nucleoplasm
is not surrounded by a nuclear membrane
1959 Kingdom Fungi
1968 Kingdom Prokaryotae proposed
1978 Two types of prokaryotic cells found

13. Classification of Prokaryotes
• Prokaryotic species: a population of cells with similar
characteristics
– Culture: grown in laboratory media at a given time
– Clone: population of cells derived from a single
parent cell
– Strain: not identical genetically different cells within a
clone
Bergey's Manlual provides a reference for identifying
bacteria in the laboratory.

14. 1-2 Types of Microorganisms
Bacteria
• Bacteria are unicellular organisms. , no nucleus
(their genetic material is not enclosed in a special
nuclear membrane), the cells are described as
prokaryotic
• Most bacteria have a peptidoglycan cell wall; not
cellulose (as in higher plants), no chitin
 Gram-Negative (20% peptidoglycan +80% lipids
 Gram-positive (80% peptidoglycan +20% Tiochoic
acid
• they divide by binary fission, and swim by flagella .
• Bacteria can use organic chemicals, inorganic
chemicals, or photosynthesis, for their nutrition
and energy.
 Asexual and sexual reproduction
 Asexual by: Binary division, Condia formation,
spore formation, fragmentation
 Sexual by lysogenic, Transformation,
Transduction, and conjection
Haemophilus influenzae

15. BASIC SHAPES OF EUBACTERIA
SPHERICAL
ROD-SHAPED
SPIRILLA
• The three major basic shapes of bacteria are bacillus, coccus, and
spiral. (Individual bacteria may form pairs, chains, clusters)

17. Most Species of Eubacteria may be Grouped
Based on Staining
• Gram-Negative
– thin layer of peptidoglycan
– Stain pink
– Endotoxins released when
bacteria die)
• Gram-Positive
– Thicker layer of
peptidoglycan
– Stain purple
– Exotoxins (out side the
cell)

19. Archaea
- Archaea consist of prokaryotic cells;
they lack peptidoglycan in
their cell walls.
- Archaea Live in extreme
environments
Include:
1) Methanogens produce methane
as a waste product from respiration
2) Extreme halophiles (halo =
salt; philic =loving) live in extremely
salty environments such as the Dead
Sea
3) Extreme thermophiles (therm =
heat) live in hot sul furous water, such
as hot springs at Yellowstone National
Park.
- Archaea are not known to cause
disease in humans.

20. Classification of Eukaryotes
• Animalia: multicellular; no cell walls;
chemoheterotrophic
• Plantae: multicellular; cellulose cell walls; usually
photoautotrophic
• Fungi: chemoheterotrophic; unicellular or
multicellular; cell walls of chitin; develop from
spores or hyphal fragments
• Protista: a catchall kingdom for eukaryotic organisms
that do not fit other kingdoms
– Grouped into clades based on rRNA

21. Fungi
- Fungi (mushrooms, molds, and
yeasts) have eukaryotic cells (cells
with a true nucleus, genetic material
(DNA), surrounded by a special
envelope called the nuclear
membrane).
- Chitin cell walls
- Molds and mushrooms are
multicellular, consisting of masses of
mycelia, which are composed of
filaments called hyphae
- Yeasts are unicellular
-Fungi obtain nutrients and energy
by absorbing organic material from
their Environment whether soil,
seawater, fresh water, or an animal
or plant host.
heterotrophic (saprobes or
parasites; symbiotic with plants

22. Characteristics
•  hypha – filaments that make up the bodies of
fungi
•  cell wall made of chitin
•  The mycellia maybe septate or non septate)
• Often reproduce asexually, but can also reproduce
sexually  by means of spores
• Classification based on how sexual spores are
produced

23. Protozoa
-Protozoa are
unicellular eukaryotes.
-May be motile via
pseudopods, cilia, or
flagella
- Protozoa Absorb or
ingest organic
chemicals through
specialized structures.
Prey
Pseudopods

24. Algae
-Algae are unicellular or
multicellular
- Eukaryotes
- Use photosynthesis for
energy
- The cell walls of many algae,
are composed of a
carbohydrate called cellulose.
- Algae produce oxygen and
carbohydrates that are used by
other organisms.
Volvox

25. Algae
-Algae are abundant in
fresh and salt water, in
soil, and in association
with plants.
- As photosynthesizers,
algae need light, water,
and carbon dioxide for
food production and
growth, but they do not
generally require organic
compounds from the
environment.
- Thus, they play an
important role in the
balance of nature.

26. Viruses
-Acellular (not cellular).
-Consist of a nucleic acid
core (DNA or RNA)
-Core is surrounded by a
protein coat
-Coat may be enclosed in
a lipid envelope
- Are replicated only when
they are in a living host
cell
HIVs

27. Viruses
• Viruses can reproduce only by using the cellular
machinery of other organisms.
• Thus, viruses are considered to be living when they
multiply within host cells they infect. In this sense,
viruses are parasites of other forms of life.
• On the other hand, viruses are not considered to be
living because outside living hosts, they are inert.
• Most can be seen only with an electron microscope

28. Multicellular Animal Parasites
- Eukaryotes
- Multicellular animals
- Parasitic flatworms and roundworms are called
helminths

29. References
• Microbiology: An Introduction Plus
MasteringMicrobiology with eText - Access Card
Package (11th Edition) Hardcover – January 2, 2012
by Gerard J. Tortora, Berdell R. Funke, Christine L.
Case.
• Some pictures from different sits.