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Binary fission
Binary fission (simple division)
–form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size
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Steps of Binary Fission
1. Cell elongates and DNA is replicated
2. Cell wall and plasma membrane begin to divide
3. Transverse septum (wall, cross-wall) forms completely around divided DNA
(a) due to continued growth of cell wall and membrane
- (b) divides contents of cell and DNA
- molecules
4. Cells separate
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Bacterial Growth Curve
- what are the phases?
- characteristics of each phase?
•Lag phase: no change in number of cells, metabolically getting ready but not yet dividing
•Log (or exponential) phase:bacteria grow in steady state, no cell death
•Stationary phase: rate of reproduction = rate of death
•Death phase: cells dying in steady state
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Which phase of the cell cycle is most sensitive to antibiotics?
- Log phase bc antibacterial target biosynthesis of
- bacteria
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6 Requirements for bacterial growth
(Factors affecting bacterial growth)
1)Temperature
2)pH
3)Oxygen
4)Water
5)Light
6)Nutrients
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Temperature
- how does it contribute to Bacterial Growth?
- 3 groups?
Optimum temp. - temp. at which maximum growth occurs
- 3 groups:
- 1. Thermophiles: 45°C - 110°C
- (e.g. hot springs, volcanoes in ocean, decomposers)
- 2. Mesophiles: 20°C - 45°C
- (e.g. environmental bacteria, pathogen)
- 3. Psychrophiles: 0°C - 20°C
- (e.g. cold springs, lakes; polar regions; refrigerator)
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Most pathogens fall into what group of temperature bacteria?
A) thermophiles
B) psychrophiles
C) mesophiles
C) mesophiles (this multiple choice question has been scrambled)
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pH
- how does it contribute to bacterial group?
- 3 groups
- Optimum pH - pH at which maximum growth occurs
- 3 groups
- 1. Alkalinophiles: 8 to 12
- (e.g. Soil bacteria)
2. Neutrophiles: 5 to 8
- 3. Acidophiles: 0 to 5
- (e.g. Helicobacter pylori - stomach ulcers)
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Most pathogens belong in what pH group?
A) alkalinophiles
B) acidophiles
C) neutrophiles
C) neutrophiles (this multiple choice question has been scrambled)
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Bacterial Growth: Oxygen
- name the 5 groups and its characteristics
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Name the following Oxygen Groups:
1.Obligate
2.Obligate anaerobic
3.Facultative
4.Microaerophile
5. Aerotolerant anaerobic
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Name 3 enzymes the detoxify oxygen radicals
- groups that each enzyme works on
- 1. superoxide dismutase
- - obligate aerobes
- - facultative anaerobes (most)
- - aerotolerant anaerobes (most)
- 2. peroxidases
- - aerotolerant anaerobes (most)
- 3. catalase- obligate aerobes
- - facultative anaerobes (most)
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water
- how it contributes to bacteria growth
All metabolically active bacteria require water
–Cells largely water
–Most nutrients, wastes soluble in water to cross cell membrane.
–Site of metabolic reactions (cytoplasm)
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Bacteria Growth:
groups that require light?
groups where light is lethal?
Very small group photosynthetic bacteria (cyanobacteria) - require UV light
- Nonphotosynthetic bacteria (eubacteria) - UV light is lethal (causes mutations)
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Name 5 nutritional requirements for bacteria growth
Basic requirements for growth:
1. Carbon:building blocks of cell components
2. Nitrogen: production of proteins, nucleic acids
3. Hydrogen: occur in organic compounds
4. Oxygen: involved in the production of energy
5: Minerals, trace elements: required in small amounts
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autorophs
- subgroups
- uses inorganic CO2 as a Carbon source
- making of own food by reducing CO2
- "self feeders"
- subgroups
- - photoautotrophs
- -chemoautotrophs
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heterotrophs
- subgroups
- uses organic compounds as Carbon source
- using ready-made organic molecules for food
- "other -feeders"
- subgroups:
- - photoheterotrophs
- - chemoheterotrophs
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chemoheterotrophs
energy source?
examples?
organic compound = energy source
- ex:
- - most bacteria
- - all protozoans
- - all fungi
- - all animals
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