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MICROBIOLOGY – ALCAMO

MICROBIOLOGY – ALCAMO. LECTURE: Physical Requirements of Bacteria. Physical Requirements of Bacteria. In order to kill bacteria, you need to know what conditions they need to survive Then if you take away what they need, death follows. 1. Temperature.

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MICROBIOLOGY – ALCAMO

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  1. MICROBIOLOGY – ALCAMO LECTURE: Physical Requirements of Bacteria

  2. Physical Requirements of Bacteria • In order to kill bacteria, you need to know what conditions they need to survive • Then if you take away what they need, death follows

  3. 1. Temperature • Each kind of MO has its own best temp. OK a little below or above = Optimum Temp, Minimum and Maximum • Reason: Enzymes only react at specific narrow temperature range

  4. Temperature Classifications: • Psychrophiles: 0 - 20C (0 - 70F) • Mesophiles: 20 - 40C (70 - 100F) • Pathogens: 37C (98.6F) • Thermophiles: 40 - 90C (100 - 200F)

  5. 2. pH • Refers to Acid/Base Balance • Acid = Free H+, Base = Free OH- • Scale: • Acid = 1 - 6 • Neutral = 7 • Base = 8 - 14 • Most MO grow best 6.4 – 7.5

  6. 3. Water • All organisms need water as solvent for chemical reactions • If water is drawn from cell, it dries out • 1 – 2% ions (salt) dries out most MO

  7. 4. Oxygen • Oxygen completes electrical circuit for respiration reactions “O” is last receiver of H+ = H2O • Most MO need air = Aerobic • Some MO have other enzyme system • No Air = Anaerobic • Some can be both = Facultative • Very low O2 requirement = microaerophilic

  8. 5. Light • Needed if photosynthetic (rare) • Absence of light needed by most MO

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