MICRO 020 Exam 2 Questions with Verified Solutions Graded A+
autoclave - Answers Very effective method of sterilization; at 15 psi (121°C) all vegetative cells
and their endospores are killed in about 15-30min.
Nonionizing radiation - Answers lower energy radiation with a longer wavelength that does not
cause ionization. Ex: cell phones, microwaves, heat lamps, and Ultraviolet Light. Used as
"germicidal" lamps found in hospital rooms, operating rooms, and cafeterias. Over time, UV light
100-400nm can form thymine dimers that cannot properly transcribe or replicate DNA which
cause DNA damage and death.
Ionizing radiation - Answers High-energy radiation with a wavelength less than 1 nm; induces
electrons to jump out of the molecule's shell creating ions(ionization). X rays and gamma rays
are examples. Principal effect of ionizing radiation is that the ionization of H2O forms highly
reactive hydroxyl radicals that kill organisms by breaking DNA bonds causing cell mutations and
death.
Antisepsis - Answers A chemical method for disinfection of the skin or mucous membranes
(living things); the chemical is called an antiseptic.
Disinfection - Answers Destruction of vegetative pathogens on inanimate objects, not including
endospores. May make use of physical or chemical methods- UV radiation, steaming, etc.
Sterilization - Answers (used on inanimate objects/material) Destruction or removal of all forms
of microbial life, including endospores, but with the possible exception of prions. Usually done
by steam under pressure or a sterilizing gas, such as ethylene oxide. Commercial sterilization
kills Clostridium botulinum endospores in canned food products.
Degerming - Answers Removal of microbes from a limited area, such as the skin around an
injection site. Mostly a mechanical removal by soap and water or an alcohol soaked swab. Ex.
Washing hands
Pasteurization - Answers purpose is to reduce bacterial populations of liquid (milk, juice) and to
destroy organisms that cause spoilage and human disease without affecting flavor. Does NOT
sterilize- spores are NOT affected. Destroys Mycobacterium tuberculosis (TB) and Coxiella
burnetii (Q n fever).
Sanitization - Answers Treatment is intended to lower microbial counts on eating and drinking
utensils to safe public health levels. May be done with high-temperature washing or by dipping
restaurant glassware into a chemical disinfectant.
-cide - Answers "to Kill" causes the outright death of microbes Ex: bactericidal, fungicidal,
virucidal
-static - Answers "stand still" Agent that inhibits the growth and multiplication of microbes but
, doesn't necessarily kill them.
disinfectants - Answers 1) Bisphenols a) triclosan in soap, toothpaste, mouthwash, b)
hexachlorophene (pHisoHex) used for surgical & hospital microbial control
disinfectants - Answers 2) Halogens a) chlorine, sodium hypochlorite 5% aka Clorox,
chloramines (Cl+ammonia) release free chlorine for water supply treatment, 3) Iodine- more
germicidal than chlorine, a) tincture of iodine used as antiseptic for wounds, b) iodophors
release iodine over a long period of time for local wounds
disinfectants - Answers 3) Alcohols- denature proteins and disrupt membranes, ETOH and
isopropyl ROH are effective in killing vegetative bacteria and fungi but non endospores or
nonenveloped viruses
*Heavy metals like Hg, Ag, Cu have germicidal effects
What is the goal of sterilization? - Answers The goal is to destroy or remove all forms of
microbial life, including endospores.
Moist heat(Physical control of microbes) - Answers kills microorganisms primarily by
coagulating proteins (denaturation), which is caused by breakage of the hydrogen bonds that
hold the proteins in their three-dimensional structure. Think sterilization. Penetrates material
faster than dry heat so need less time and lower temps. Boiling H2O not a sterilization agent
because of endospores and some viruses.
Dry heat(Physical control of microbes) - Answers kills by oxidation effects. Types 1) direct
flame: incinerates microbes rapidly ex. Bunsen burner inoculating loop 2) hot air ovens: 170 deg
C for at least 2 hours
Filtration(Physical control of microbes) - Answers is the passage of a liquid or gas through a
screenlike material (filter) with pores small enough to retain microorganisms. Used to remove
microbes from a solution or gas in food industries and laboratories.
Liquid filtration(Physical control of microbes) - Answers uses membrane filter to sterilize
culture media or any liquid that can't tolerate heat such as serum, blood products, drugs IV
fluids, enzymes. Can be used for bacterial count of a petri dish.
Air filtration(Physical control of microbes) - Answers Some operating theaters and rooms
occupied by burn patients receive filtered air to lower the numbers of airborne microbes. Think
HEPA (high efficiency particulate air) filters.
*Low temperatures- such as in refrigerators and freezers slows growth but does not kill-
bacteriostatic, the metabolic rate is reduced and now cant reproduce or make toxins
*Desiccation- drying in the absence of H2O, microbes can't reproduce or grow but remain viable
for years, viruses and endospores are resistant to desiccation
autoclave - Answers Very effective method of sterilization; at 15 psi (121°C) all vegetative cells
and their endospores are killed in about 15-30min.
Nonionizing radiation - Answers lower energy radiation with a longer wavelength that does not
cause ionization. Ex: cell phones, microwaves, heat lamps, and Ultraviolet Light. Used as
"germicidal" lamps found in hospital rooms, operating rooms, and cafeterias. Over time, UV light
100-400nm can form thymine dimers that cannot properly transcribe or replicate DNA which
cause DNA damage and death.
Ionizing radiation - Answers High-energy radiation with a wavelength less than 1 nm; induces
electrons to jump out of the molecule's shell creating ions(ionization). X rays and gamma rays
are examples. Principal effect of ionizing radiation is that the ionization of H2O forms highly
reactive hydroxyl radicals that kill organisms by breaking DNA bonds causing cell mutations and
death.
Antisepsis - Answers A chemical method for disinfection of the skin or mucous membranes
(living things); the chemical is called an antiseptic.
Disinfection - Answers Destruction of vegetative pathogens on inanimate objects, not including
endospores. May make use of physical or chemical methods- UV radiation, steaming, etc.
Sterilization - Answers (used on inanimate objects/material) Destruction or removal of all forms
of microbial life, including endospores, but with the possible exception of prions. Usually done
by steam under pressure or a sterilizing gas, such as ethylene oxide. Commercial sterilization
kills Clostridium botulinum endospores in canned food products.
Degerming - Answers Removal of microbes from a limited area, such as the skin around an
injection site. Mostly a mechanical removal by soap and water or an alcohol soaked swab. Ex.
Washing hands
Pasteurization - Answers purpose is to reduce bacterial populations of liquid (milk, juice) and to
destroy organisms that cause spoilage and human disease without affecting flavor. Does NOT
sterilize- spores are NOT affected. Destroys Mycobacterium tuberculosis (TB) and Coxiella
burnetii (Q n fever).
Sanitization - Answers Treatment is intended to lower microbial counts on eating and drinking
utensils to safe public health levels. May be done with high-temperature washing or by dipping
restaurant glassware into a chemical disinfectant.
-cide - Answers "to Kill" causes the outright death of microbes Ex: bactericidal, fungicidal,
virucidal
-static - Answers "stand still" Agent that inhibits the growth and multiplication of microbes but
, doesn't necessarily kill them.
disinfectants - Answers 1) Bisphenols a) triclosan in soap, toothpaste, mouthwash, b)
hexachlorophene (pHisoHex) used for surgical & hospital microbial control
disinfectants - Answers 2) Halogens a) chlorine, sodium hypochlorite 5% aka Clorox,
chloramines (Cl+ammonia) release free chlorine for water supply treatment, 3) Iodine- more
germicidal than chlorine, a) tincture of iodine used as antiseptic for wounds, b) iodophors
release iodine over a long period of time for local wounds
disinfectants - Answers 3) Alcohols- denature proteins and disrupt membranes, ETOH and
isopropyl ROH are effective in killing vegetative bacteria and fungi but non endospores or
nonenveloped viruses
*Heavy metals like Hg, Ag, Cu have germicidal effects
What is the goal of sterilization? - Answers The goal is to destroy or remove all forms of
microbial life, including endospores.
Moist heat(Physical control of microbes) - Answers kills microorganisms primarily by
coagulating proteins (denaturation), which is caused by breakage of the hydrogen bonds that
hold the proteins in their three-dimensional structure. Think sterilization. Penetrates material
faster than dry heat so need less time and lower temps. Boiling H2O not a sterilization agent
because of endospores and some viruses.
Dry heat(Physical control of microbes) - Answers kills by oxidation effects. Types 1) direct
flame: incinerates microbes rapidly ex. Bunsen burner inoculating loop 2) hot air ovens: 170 deg
C for at least 2 hours
Filtration(Physical control of microbes) - Answers is the passage of a liquid or gas through a
screenlike material (filter) with pores small enough to retain microorganisms. Used to remove
microbes from a solution or gas in food industries and laboratories.
Liquid filtration(Physical control of microbes) - Answers uses membrane filter to sterilize
culture media or any liquid that can't tolerate heat such as serum, blood products, drugs IV
fluids, enzymes. Can be used for bacterial count of a petri dish.
Air filtration(Physical control of microbes) - Answers Some operating theaters and rooms
occupied by burn patients receive filtered air to lower the numbers of airborne microbes. Think
HEPA (high efficiency particulate air) filters.
*Low temperatures- such as in refrigerators and freezers slows growth but does not kill-
bacteriostatic, the metabolic rate is reduced and now cant reproduce or make toxins
*Desiccation- drying in the absence of H2O, microbes can't reproduce or grow but remain viable
for years, viruses and endospores are resistant to desiccation
