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Microbiology notes

Lecture 1:
Steps of binary fission:

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Replication of DNA
Growth of the cell
Segregation of DNA
Splitting of the cell

Bacterial structures and their functions:
1
...
Pili (fimbriae)
Classification:
1- Common pili: used for adhesion
2- Sex pili: used for conjugation
3
...
Cell membrane
Functions:
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Protects inner structures of the cell
Breaks down nutrients and produces ATP
Site of bacterial respiration
Site of (membrane lipids, cell wall polymers, and DNA) synthesis
Selectively permeable
Excretion of exoenzymes and pathogenicity proteins
Mediation of chromosomal segregation during replication

5
...
Cell wall
Functions:
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Responsible for the shape of the cell
Helps with communication with the surroundings
Protects the cell’s interior structures
Protects the cell against osmosis
Is a target site for antibiotics
Used to differentiate different types of bacteria
Takes part in cell division

7
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Teichoic acids
9
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Endospores
Spore-forming bacteria are: Bacillus and Clostridium

Bacterial classification according to their cell wall:

1- Protoplasts: Bacterium without a cell wall
...


Lecture 2
Factors regulating the growth of bacteria:
A- Physical factors:

1- pH:
-Acidophiles = 1
...
4 (Helicobacter pylori)
-Neutrophiles = 5
...
5 (Vibrio cholerae)

2 – Temperature

-Psychrophiles = 15C – 20C (some can grow at 0C)
-Mesophiles = 25C – 40C
-Thermophiles = 50C – 60C

3- Osmotic pressure and salt concentration of the solution can affect bacterial growth
...
coli,
Staphylococcus
4- Aerotolerant: Don’t use Oxygen, but can still survive in an environment with
Oxygen present (Lactobacillus
...


C- Nutritional factors:

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Carbon: for the production of (Proteins, lipids, and carbohydrates)
Nitrogen: needed for (amino acids and nucleotides)
Sulfur: needed for (amino acids and coenzymes)
Phosphorus: needed for (ATP, Phospholipids, and nucleotides)
Vitamins: used as a coenzyme (some bacteria in the intestines produce
vitamin K, and some create B vitamins)
6- Trace elements: cofactors in enzymatic reactions (copper Cu, iron Fe,
zinc Zn, potassium K, calcium Ca, NaCl, etc)
...

2- Heterotrophic: Carbon is obtained from organic compounds in the
environment
...


Bacterial growth curve:

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Lag phase: Preparation for cell division
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Log phase: Rapid cell division
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of cells produced > No
...

Stationary phase: slow cell division
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cells produced = No
...

Decline phase: No cell division
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of cells produced < No
...


*Cells are most susceptible to environmental changes (radiation, antibiotics)
during the log phase

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