Ch 16 Sterilization - Micro Lab

Front 1

sterilization

Back 1

the complete elimination of vegetative bacterial cells

Front 2

methods of sterilization

Back 2

• irradiation
• heat
• high pressure
• filtration
• chemicals

Front 3

ionizing radiation sterilization

Back 3

• includes x-ray & gamma rays that force electrons out of their shells creating ions
• ions combine w/ cellular water and the free radicals generated affect cell metabolism & physiology
• does NOT have a direct effect on nucleic acids (DNA)
• commonly used to sterilize disposable medical tools & equipment

Front 4

What are the advantages of ionizing radiation sterilization?

Back 4

during the sterilization process the penetrating abilities of the x-rays and gamma rays allow:

• items can remain at normal temperatures
• containers may remain completely sealed

Front 5

heat sterilization

Back 5

• most common form of sterilization
• at extremely high temperatures even the enzymes of thermophilic bacteria will become denatured; killing the bacteria
• moist heat is more effective than dry heat

Front 6

steam sterilization

Back 6

• accomplished using an autoclave in which steam under pressure is applied to the chamber
• standard rule is 121°C at 15 psi for 15 min
• for larger volumes the amount of time should be increased

Front 7

dry heat sterilization

Back 7

• used for equipment that must remain dry
• less effective than moist heat because there is no water
• higher temperatures and longer sterilization temperatures are required
• temp greater than 180°C and times greater than 3 hours

Front 8

When is filtration sterilization required?

Back 8

when selective and differential media contain heat sensitive ingredient (X-Gal, antibiotics, etc) these molecules will be destroyed at sterilization temperatures

Front 9

sterile filtration

Back 9

• uses a pore size of ~0.2 µm into is a sterile container
• smallest size of normal bacteria is ~0.22 µm
• bacteria are trapped in the filter

Front 10

chemical sterilization

Back 10

ex: formaldehyde can be used to sterilize glassware

residues may affect experimental results