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Ch. 9 - Coggle Diagram
Ch. 9
Culture Media
Liquid (sterilized using filtration), agar, or semi-solid
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EMB agar is solid, complex, selective and differential
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Counting Bacteria
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Petroff-House: P (Inexpensive, fast) C (High # of bacteria needed, counts live and dead cells)
Bacterial Growth Curve
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Log phase (exponential): Organisms actively dividing, nutrients decreasing (best time to test organisms because they are metabolically active) (Penicillin most effective)
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Death: No nutrients available, organisms declining
Food spoilage
Viruses are responsible for majority of outbreaks, staphylococcus aureus most common cause
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Microbial Growth
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Requirements
Physical: Temp, pH, osmotic pressure
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Binary Fission
Increase in #, not size, reproduce by binary fission
Process: 1. (Cell elongates, DNA replicated) 2. (Cell wall + plasma membrane begins to divide) 3. (Cross-wall forms around divided DNA) 4. (Cells serparate)
Binary fission: time required for cell to divide, about 1-3 hours, others 24+.
Physical Requirements
Temp (C)
Psychrophiles (-10-20) Psychrotrophs (0-30) Mesophiles (10-50) Thermophiles (40-70) Hyperthermophiles (70-110)
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pH
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Fungi (molds + yeasts): 5-6, acidic foods
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Biofilms
Planktonic bacteria. Attaches to rocks, teeth, shower tiles
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