BIOL 271 Microbiology w/ Lab | Module 1. Intro to microbiology,
prokaryotes vs eukaryotes, cellular organelles and arrangements.
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1.Eukaryotic microbes vs Prokaryotic microbes
➢ Eukaryotic Microbe: EX: fungi
True nucleus (enclosed within nuclear membrane)
Has organelle: Mitochodria/golgi bodies/endoplasmic reticulum
The nucleus divides by mitosis
➢ Prokaryotic Microbes: EX: bacteria
No nuclear membrane, no nucleolus
Retain basic cell structure and metabolic enzyme
No mitochondria\golgi bodies\endoplasmic reticulum (except for ribosome)
2. Bacterial cell wall
Two types: Gram-positive and Gram-negative
➢ Peptidoglycan layer
Backbone: composed of alternating N-acetyl glucosamine and N-acetyl muramic acid connected
by β-1,4 glycosidic bone.
Tetrapeptide side chain: link to N-acetyl muramic acid
Pentapeptide cross bridge: composed of five glycines (only in G+ bacteria), In many Gram-
negative cell walls, the cross-bridges consist of a direct peptide linkage
Special component of Gram-positive cell wall ---Teichoic acid:
1
,The teichoic acids extend through the cell wall and constitute major surface antigens of the
bacteria.
Special component of Gram-negative cell wall ---Outer membrane
Lipid A： Associated with the toxicity of LPS
Has no species specificity
Specific polysaccharide： O antigen
3. Koch’s Postulates
1) The organism must always be present, in every case of the disease.
2) The organism must be isolated from a host containing the disease and grown in pure
culture.
3) Samples of the organism taken from pure culture must cause the same disease when
inoculated into a healthy, susceptible animal in the laboratory.
4) The organism must be isolated from the inoculated animal and must be identified as the
same original organism first isolated from the originally diseased host
4. Coccus
Cocci (singular: coccus): spherical
Pairs (diplococcus)
Chain (streptococcus)
Cubical bundle (tetrad, sarcina)
Grape-like irregular cluster (staphylococcus)
5. Bacillus
2
, Bacilli (singular: bacillus) : rods
6. capsule
Some bacteria have a extracellular polymer surrounding the cell.
a. When the polymer forms a condensed well-defined layer, it is called a capsule. But when
it is loose, and appear to be detached from the cell it is called slime layer.
b. Capsules usually consist of polysaccharide; however, in certain bacilli they are composed
of a polypeptide.
c. Capsule is not essential to cell viability
Function of Capsule:
1) Attachment
2) Protect the cells from phagocytosis
3) Act as a barrier to antimicrobial substances in the blood
7. flagella
Bacterial flagella are thread-like appendages. They are the organs of locomotion and provide
motility for bacteria. they can provide motility for bacteria, allowing the cell to swim toward
food and away from poisons.
Bacterial flagella are composed of protein(flagellins). They are highly antigenic (H antigens)
8. pili
Pili are rigid surface appendages, which are shorter and finer than flagella.
Two kinds of pili:
• Ordinary pili (short, straight bristles)
Ordinary pili play a role in the adherence of pathogenic bacteria to host. And are related to the
virulence of pathogenic bacteria.
• Sex pili (long, flexible)
Sex pili are responsible for the attachment of donor and recipient cells in bacterial conjugation.
Therefore, are related to the transfer of drug-resistance, virulence.
3
, 9. spore
Spore refers to a reproductive cell capable of developing into a new organism endospores are
specific to bacteria, while spores can be found in various organisms, including fungi and plants
10. Gram-stain
Gram-positive: purple
Gram-negative: pink
11. LPS: refer to key point number 2
12. Plasmid
Plasmids are small, circular, covalently closed, double-stranded DNA molecules. They are capable of self-
replication and carry genes coding for some properties of the bacteria, such as antibiotic resistance,
virulence。Plasmids are not essential for cellular survival.
13. Endospores
A number of gram-positive bacteria can form a special dormant structure under conditions of nutritional
depletion, called an endospore
Endospores are highly resistant to environmental factors such as desiccation, heat, chemical agents.
Endospores can exist for a very long time, and then germinate.
Endospores elicit disease only when they enter the host and germinate to produce vegetative cells.
Endospores are difficult to decontaminate with standard disinfectants. A temperature of 121℃ for 15
minutes is utilized to kill spores.
14. Autotroph vs Heterotroph
4
prokaryotes vs eukaryotes, cellular organelles and arrangements.
|LockDown Browser | Portage Learning.
1.Eukaryotic microbes vs Prokaryotic microbes
➢ Eukaryotic Microbe: EX: fungi
True nucleus (enclosed within nuclear membrane)
Has organelle: Mitochodria/golgi bodies/endoplasmic reticulum
The nucleus divides by mitosis
➢ Prokaryotic Microbes: EX: bacteria
No nuclear membrane, no nucleolus
Retain basic cell structure and metabolic enzyme
No mitochondria\golgi bodies\endoplasmic reticulum (except for ribosome)
2. Bacterial cell wall
Two types: Gram-positive and Gram-negative
➢ Peptidoglycan layer
Backbone: composed of alternating N-acetyl glucosamine and N-acetyl muramic acid connected
by β-1,4 glycosidic bone.
Tetrapeptide side chain: link to N-acetyl muramic acid
Pentapeptide cross bridge: composed of five glycines (only in G+ bacteria), In many Gram-
negative cell walls, the cross-bridges consist of a direct peptide linkage
Special component of Gram-positive cell wall ---Teichoic acid:
1
,The teichoic acids extend through the cell wall and constitute major surface antigens of the
bacteria.
Special component of Gram-negative cell wall ---Outer membrane
Lipid A： Associated with the toxicity of LPS
Has no species specificity
Specific polysaccharide： O antigen
3. Koch’s Postulates
1) The organism must always be present, in every case of the disease.
2) The organism must be isolated from a host containing the disease and grown in pure
culture.
3) Samples of the organism taken from pure culture must cause the same disease when
inoculated into a healthy, susceptible animal in the laboratory.
4) The organism must be isolated from the inoculated animal and must be identified as the
same original organism first isolated from the originally diseased host
4. Coccus
Cocci (singular: coccus): spherical
Pairs (diplococcus)
Chain (streptococcus)
Cubical bundle (tetrad, sarcina)
Grape-like irregular cluster (staphylococcus)
5. Bacillus
2
, Bacilli (singular: bacillus) : rods
6. capsule
Some bacteria have a extracellular polymer surrounding the cell.
a. When the polymer forms a condensed well-defined layer, it is called a capsule. But when
it is loose, and appear to be detached from the cell it is called slime layer.
b. Capsules usually consist of polysaccharide; however, in certain bacilli they are composed
of a polypeptide.
c. Capsule is not essential to cell viability
Function of Capsule:
1) Attachment
2) Protect the cells from phagocytosis
3) Act as a barrier to antimicrobial substances in the blood
7. flagella
Bacterial flagella are thread-like appendages. They are the organs of locomotion and provide
motility for bacteria. they can provide motility for bacteria, allowing the cell to swim toward
food and away from poisons.
Bacterial flagella are composed of protein(flagellins). They are highly antigenic (H antigens)
8. pili
Pili are rigid surface appendages, which are shorter and finer than flagella.
Two kinds of pili:
• Ordinary pili (short, straight bristles)
Ordinary pili play a role in the adherence of pathogenic bacteria to host. And are related to the
virulence of pathogenic bacteria.
• Sex pili (long, flexible)
Sex pili are responsible for the attachment of donor and recipient cells in bacterial conjugation.
Therefore, are related to the transfer of drug-resistance, virulence.
3
, 9. spore
Spore refers to a reproductive cell capable of developing into a new organism endospores are
specific to bacteria, while spores can be found in various organisms, including fungi and plants
10. Gram-stain
Gram-positive: purple
Gram-negative: pink
11. LPS: refer to key point number 2
12. Plasmid
Plasmids are small, circular, covalently closed, double-stranded DNA molecules. They are capable of self-
replication and carry genes coding for some properties of the bacteria, such as antibiotic resistance,
virulence。Plasmids are not essential for cellular survival.
13. Endospores
A number of gram-positive bacteria can form a special dormant structure under conditions of nutritional
depletion, called an endospore
Endospores are highly resistant to environmental factors such as desiccation, heat, chemical agents.
Endospores can exist for a very long time, and then germinate.
Endospores elicit disease only when they enter the host and germinate to produce vegetative cells.
Endospores are difficult to decontaminate with standard disinfectants. A temperature of 121℃ for 15
minutes is utilized to kill spores.
14. Autotroph vs Heterotroph
4
