Chapter 7 Microbial Growth
Terms
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- Microbe of the Day: Clostridium botulinum
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Spore-former; lives in soil
Spores ingested, germinate and produce botulinum toxin --> paralysis
Strict anaerobe
Gram positive rod - Growth of Microbes
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o Increase in number of cells, not cell size
o One cell becomes colony of millions of cells
o Control of growth is important for
– infection control
– growth of industrial and biotech organisms - Factors Regulating Growth
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o Nutrients
o Environmental conditions: temperature, oxygen, pH, osmotic pressure
o Generation time - Chemical Requirements
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o C (50% of cell’s dry weight)
o H, O, N, P, S
– Nitrogen fixation: transform N2 into NH4+
o Trace elements
o Needed for structural molecules and enzymes - Organic Growth Factors
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o Source of energy
o Vitamins (coenzymes)
o Some amino acids, purines and pyrimidines. - Nutritional Categories
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o Carbon sources
CO2 = autotroph
organic = heterotroph
o Energy sources
sunlight = phototroph
organic = chemotroph - Saprobe
- lives on organic matter of dead organisms
- Parasite
- lives on organic matter of living host = pathogen
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Nutrient Uptake
Osmosis - Movement (diffusion) of water
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Nutrient Uptake
Isotonic - same solute concentration inside and out; no water movement
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Nutrient Uptake
Hypotonic - more solutes inside; water enters cell
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Nutrient Uptake
Hypertonic - more solutes outside; water leaves cell
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Movement of Molecules
Facilitated diffusion - higher to lower concentration, carrier molecule
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Movement of Molecules
Active transport - lower to higher concentration, takes energy
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Movement of Molecules
Group translocation - lower to higher concentration with chemical change