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23 Cards in this Set
- Front
- Back
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Bacterial growth |
Bacterial growth is by BINARY FISSION: 1) Cells elongate and DNA replicates 2) CW & plasma membrane grow INWARDS 3) Cross-walls form completely around divided DNA, then cells separate to produce daughter cells. |
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Bacterial growth curve |
X- AXIS = NO OF GENERATIONS Y- AXIS = TIME |
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Lag phase |
Organism getting used to the medium/environmemt. Upregulating enzymes for growth. |
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Log phase |
Grows exponentially |
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Stationary phase |
Dying cells equal to new cells. So no net increase in VIABLE cells. Nutrient become depleted, pH changes, build-up of toxic waste and oxygen levels deplete. |
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What is growth constrained by? |
1. Nutrients 2. Wate products 3. Quorum sensing (bacterial communication) 4. Physical constraints (temp, pH, water) |
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What are the 2 options for growth? |
1. Respiration 2. Fermentation |
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Respiration |
COMPLETE OXIDATION GLUCOSE -> CO2 + h20 Needs final electron acceptor or FEA Common FEA = Oxygen!! |
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Fermentation |
INCOMPLETE OXIDATION OBLIGATE |
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OBLIGATE AEROBES |
Need oxygen |
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Facultative Aerobes |
Prefer oxygen |
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Aerotolerant aerobes |
Ignores oxygen |
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STRICT ANAEROBES |
Oxygen is toxic for these bacteria. They don't survive in oxygen atmosphere. E.g clostridium botulism. |
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PH |
pH - negative log = 1pH unit ff 10 fold change in H |
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Low temp |
Psychrophiles |
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Mid range temp |
Mesophiles |
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High temp |
thermophiles |
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What is danger zone in temp? |
20 to 50 degrees is danger zone due to bacterial growth |
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Filtration ff |
Removal of particles from liquid and gases. E.g HEDA filters sterilise air |
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What is water activity (aw) ? |
How much h20 is available HIGHER SOLUTE means LOWER aw |
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How do we stop microbial growth? |
1. Osmotic shock, where the solute e.g DNA etc is at a higher pressure within the cell. 2. Put in salt 3. GN less tolerant than GP as it used to salt condition e.g sweat on skin. |
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Antiseptic |
BIOCIDAL - kills organism |
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Antibiotic |
Biostatic (inhibits growth not kill) |
