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Microbiology Techniques. A. Pure culture techniques Pleomorphism Koch/Pasteur. Gelatin gives way to AGAR. Microbiology Techniques cont…. Microbiology Techniques cont…. Microbiology Techniques – Culturing microorganisms. log e N. N. t. t. Microbiology Techniques cont….. .
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Microbiology Techniques • A. Pure culture techniques • Pleomorphism • Koch/Pasteur. Gelatin gives way to AGAR
logeN N t t Microbiology Techniques cont….. • B. Sterilisation. • Physical. Chemical. Filtration. • Kinetics of death. Usually FIRST ORDER. • logeNt =logeNo - kt k=death constant
Microbiology Techniques cont….. • Thermal death point. 10ml for 10 minutes • E.coli vegetative cells 55oC Bacillus sp spores 120oC • Decimal reduction time. Time to kill 90%. • C. Use of Heat. • 50 - 70oC vegetative cells. PASTEURISATION. • 100oC Some spores and viruses. • 110-120oC Most everything. • AUTOCLAVE USUALLY 121oC 15psi • MOIST/WET HEAT better than DRY HEAT OVENS • D. Radiation. • UV, X rays, gamma radiation commonly used
Microbiology Techniques cont….. • E. Filtration. • Usually use 0.22 m pore cellulose acetate/nylon filters. Not effective for virus removal. They are filterable • F. Impaction. • Physical force using striking action • G. Chemical agents. • Phenol Disinfectant Phenol Coefficient • Halogens Cl Br • Oxidants H2O2 • Alkylating agents Formaldehyde • Detergents • Metals Hg • Alcohols DIRECTED READING: Practical manual. Prescot. Ch2 Microscopy Ch5 Media. Ch6 Growth