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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
Lecture-2- Eukaryotes & Prokaryotes
The following table illustrates the main differences between Eukaryotic cells &
Prokaryotic cells:
Structure
Definite Nucleus
Nuclear membrane
Chromosome
Cell envelope
Nucleolus
Organelles.(mitocondria,
Golgi apparatus,
ribosome
Replication
Representative
organisms
Eukaryotic cells
Yeas
Yeas
Multiple
Yeas, have flexible cell mem.
Except fungi have rigid cell wall
with chitin
Yeas
Prokaryotic cells
No
No
Single
Yeas, have rigid cell wall
that contain peptidoglycan
No
Yeas
No
Large 80 S ribosome
By mitosis
Small 70 S ribosome
By binary fission
Animals, plant, protozoa, fungi
Bacteria
The following table illustrates the comparison of medical important organism
characteristic
Cells
Viruses
No cell (particle)
Bacteria
Yeas
Diameter(μm)
0.02-0.3 smallest MO
1-0.5
Nucleic acid
Either DNA or RNA
Nature of outer
surface proteins
Capsid and lipoprotein
envelope
ribosome
absent
Produce many copies of
Nucleic acid and protein,
then, reassemble into
multiple progeny viruses.
They are replicate only
within living cell
none
Methods of
Replication
Motility
1
Both
rigid cell wall
that contain
peptidoglycan
70 S
Fungi
Yeas
3-10
(yeast)
Both
rigid cell
wall with
chitin
80 S
Protozoa
Yeas
15-25
trophozoite
Both
Flexible cell
mem.
Except
80 S
By binary
fission
Budding
or mitosis
mitosis
some
none
most
Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
Scientific name:
The binomial system of published by C. Linnaeus. The genus and species are significant
taxonomic uses in binomial nomenclature for each organism. First name for genus and
second name for species. First letter of genus should be written in capital letter, whereas
first letter of species, must be write in small. Name of genus and species for any organism
must be write in Italic from or place line under each genus and species.
Ex: Staphylococcus aureus.
Name of bacteria are derived from
1. The name of disease that caused by bacteria. Ex: Vibrio cholerae= causes cholerae.
2. The locality where the bacteria was first isolated. Ex: Escherichia coli=from colon.
3. The scientists responsible for isolating bacteria. Listeria= Lister.
4. Properties of bacterial morphology and physiology. Staphylococcus aureus= cluster.
Classification of MO
The importance of classification:
1. To establish the criteria for identification.
2. To arrange similar organisms in to groups.
3. To provide information about how organism evolved.
4. To avoid the confusing in the information about different types of organisms.
All types of organisms classified in to five kingdom; monera, protista, fungi, plantae,
and animalia. The following table illustrates the kingdom.
Kingdom
Types of cell
Organism
monera
Prokaryotes
Bacteria
protista
Eukaryotes
Protozoa
fungi
Eukaryotes
fungi
plantae
Eukaryotes
plant
animalia
Eukaryotes
Man,
animals
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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
Shapes and size of bacteria and patterns of arrangement
1. spherical (cocci); A: singular cocci. B: diplococci (pairs of cells).
C: streptococci (chains). D:staphylococci (clusters or grape like).E: tetrad: four cocci
2. Bacilli (rod like); A: singular bacillus. B: diplobacilli (pairs of cells).
C: streptobacilli (chains). D:coccobacilli ( spherical to rod)
3. spirochetes: spirilium (spiral). F vibrio (comma).
4. pleomorphic (appear in many shape).
 Bacterial size
Most disease causing by bacteria range in size from 0.2 -5 μm in diameter and 0.4-14
μm in length approximately. The bacterial cells are about the size of mitochonderia.
Structure and function of bacterial cell
 Cell wall
The bacteria are surrounding by rigid cell wall. The principle structural component of
cell wall is peptidoglycan. Peptidoglycan (PG) is complex of polysaccharide and
polypeptide. Most bacteria are classified according to reaction of Gram stain with
components of cell wall into major groups; Gram positive & Gram negative bacteria.
The cell wall of Gram positive differs from Gram negative. Gram positive bacteria
have thick cell wall and teichoic acid, while Gram negative bacteria have thin cell
wall and no teichoic acid. The large amounts of PG make Gram positive bacteria
susceptible to antibiotics (penicillin) that inhibit cell wall synthesis.
All bacteria have cell wall except Mycoplasma.
Function of cell wall:
1. Protection the internal structures.
2. Give shape the cell.
3. Contain component which toxic to host cell.
 Cell membrane (plasma membrane):
Cell membrane is composed of two layers of lipid (the lipids linked to proteins and to
polysacchrides). It is located under cell wall.
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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
Gram negative bacteria have inner and, whereas Gram positive bacteria have only inner
cell membrane. The space between inner and outer membrane called periplasmic space.
Outer cell membrane of Gram negative bacteria is composed of lipopolsaccharide (LPS)
and lipoproteins. LPS acts as endotoxine.
Function of cell membrane
1. Control on inflow of metabolites to from cell by control on active transport of
molecules into cell because it has selective permeability.
2. Energy generation by oxidative phosphorylation.
3. Secretion of enzyme and toxin.
4. Synthesis of precursors of cell wall (have important role in synthesis of cell wall).
Nucleoid
The bacterial genome consists of a single chromosome. It is not surrounded by nuclear
membrane. Some bacteria have small, circular of DNA (plasmid) as free in cytoplasm.
Ribosome
It is composed of several RNA and proteins. The 70s unit is composed of two small
subunits (50s and 30s), while eukaryotic ribosome is consist of 80s (60s and 40s).
The important role of it:
1. The ribosomes are site of protein synthesis.
2. The differences in rRNA and protein constitute of bacteria, the basis of selective
action of several antibiotics (tetracycline) that inhibit bacterial protein synthesis.
External structures
A – Capsule: some bacteria have capsule. It is a gelatinous layer covering the entire
bacterium, may be composed polysaccharide or poly peptide. Capsule importance:
1. Protection against deleterious agents (Lytic enzyme).
2. Contribute to virulence of many bacteria (inhibiting phagocytosis) &it play role in
adherence of bacteria to human tissues.
3. it is used as antigen (K- antigen)in certain vaccines.
4. specific identification of MO.
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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
Flagella:
It is long filamentous appendages. They are organ of locomotion The flagella may be
located at one end or both ends of bacteria, in other they are over the outer surface.
Most rod bacteria have flagella (motile), while most cocci are non motile. Function:
1. organ for motility.
2. may play role in pathogenesis.
3. act as antigen (H- antigen).
Pili (Fimbriae)
It is hair like filaments that extend from cell membrane. They are shorter and
straighter than flagella. They are fond mainly in Gram negative bacteria.
Pili have important role:
1. they mediate the attachment of bacteria to specific receptor on human cells.
2. have role in transfer of genetic material between bacteria through conjugation.
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