Exam 2 Part 2 Flashcards
UV is a type of what
electromagnetic energy
this is the distance between adjacent wave crests, measured in nm
wavelength
what are the three categories of ultraviolet light
UV A (315-400 nm), UV B (280-315 nm), UV C (100-280 nm)
what wavelength is the most detrimental
exposure to this for more than a few min usually results in damage or death
UV C
what is the germicidal effect related to
time of exposure, lamp intensity, and distance to the target
what is effectiveness diminished by
dust
what is ultra violet light commonly used for
to disinfect labs and health care environments
why is prolonged exposure lethal
DNA absorbs UV radiation at 254 nm the energy is used to form new covalent bond between adjacent pyrimidines
what are the pyrimidine dimers
cytosine-cytosine, cytosine-thymine, thymine-thymine
what do the pyrimidine dimers do
distort the DNA molecule and interfere with DNA replication and transcription
what is light repair also known as
photoreactivation
when is the repair enzyme activated by visible light and reverses the original reaction
light repair
what is the repair enzyme
DNA photolyase
what is dark repair also known as
excision repair(involves multiple enzymes)
what enzymes does dark repair include
endonuclease, helicase, DNA polymerase 1, and DNA ligase
what does the endonuclease do
breaks two covalent bond in backbone
what does helicase do
removes the nucleotides in the damaged segment
what does DNA polymerase do
synthesizes the new strand
what does the DNA ligase do
forms a covalent bond between the new and original strands (closes gap)
what can ultraviolet radiation be used in due to lethal effects on bacterial cellls
decontamination
this is the ability of inability to live in the presence of ozygen
aeroteolerance
this kills unwanted microbes and removes most of the free oxygen from the media as well
sterilizing the media in an autoclave
what is found at the top
aerobic
what is found at the bottom
anaerobic
these are organisms that require oxygen for aerobic respiration
grow at the top where O2 is plentiful
strict aerobes
grow in the presence or absence of oxygen
can respire BOTH aerobically and anaerobically
grow throughout the medium but dense at top
facultaitve anaerobes
why are facultative anaerobes denser at top
due to higher ATP yield from aerobic
these live uniformly throughout the medium
aerotolerant anaerobes
survive only in environments containing lower than atmospheric levels of oxygen
microaerophiles
can survive only if carbon dioxide levels are elevated
capnophiles
organisms for which even small amounts of oxygen are lethal
strict anaerobes
these cause an oxygen gradient
agar deep stabs
this is enriched with yeast extract to promote growth of a broad range of organisms
tryptic soy agar
what are agar deeps prepared with and why
10 mL of medium, the extra depth ensure bottom portion of medium is anaerobic
why is stab incoculated with incoculating needle
to introduce as little air as possible
what does the location of growth indicate
the organism’s aerotolerance
when is air removed
when agar is autoclaved
once the agar cools and solidifies, what occurs
air diffuses back into the agar and a concentration gradient is formed
this is well adapted for cultivation of strict anaerobes and microaerophiles
fluid thioglycollate broth
what are key components of FTB
yeast extract, pancreatic digest of casein, dextrose, sodium thioglycollate, L-cytosine, and reazurin
this is an indicator of O2(pink) when presnet and colorelss when reduced
reazurin
why is a small amount of agar added
to slow oxygen diffusion
what is FTB used for
to illustrate microbial growth representing all levels of oxygen tolerance
this is a plastic jar in which to create anaerobic, microaerophilic, or CO2 enriched conditions
GasPak (anaerobic systems)
what are the components required for anaerobic growth
chemical gas generator, paper indicator strip, and palladium
what does palladium do
catalyzes a reaction between hydrogen and free O2 to create water
