Lab 24 - Killing by Ultraviolet Light

chemical, physical, antimicrobial

Methods for controlling or preventing the growth of microorganisms include ___ methods, ___ methods, and ___ drugs.

gamma, ultraviolet

The two forms of radiation that are used to kill microorganisms are ___ radiation and ___ radiation.

gamma

___ radiation has its greatest impact when it collides with molecules in the cell, creating free radicals which are toxic.

ultraviolet

___ radiation (a.k.a. nonionizing radiation) primarily kills by damaging DNA and RNA by effecting bonding relationships within the molecule.

thymine, cytosine dimers

Ultraviolet radiation affects bonding relationships within the molecule; A major example is the formation of ___ or ___ ___ (bonds between two adjacent pyrimidines in the DNA strand).

mutations

UV can lead to ___.

200, 290, DNA

UV with a wavelength between ___ - ___ nanometers (nm) is the most lethal as they are absorbed the most by ___.

prions, enveloped viruses

The most susceptible microbes are ___, while the least are ___ ___.

penetrating

One of the biggest limitations in the use of UV light as a disinfecting or sterilizing method is its poor ___ ability.

germicidal

The 254 nm UV-C light emitted by ___ lamps is valuable for killing microbes in the air and on surfaces such as inside transfer hoods for tissue culture, clean rooms, and operating rooms.

0, 1, 5

For the “Killing by Ultraviolet Light” lab, three Petri dishes are quartered into sections. One half is inoculated with S. aureus while the other has Serratia. One side of each inoculum is covered while the UV lamp is on for either ___, ___, or ___ minutes depending on which plate.

3, agar

For the “Killing by Ultraviolet Light” lab ___ (number) ___ (type) plates are used to demonstrate UV killing ability of the inoculums.