BIOL 2051 LSU LAB FINAL EXAM QUESTIONS AND
ANSWERS 100% CORRECT
antibiosis - answer a symbiotic relationship between two organisms in which there is
inhibition, injury, or killing of one organism by another
what does penicillin interfere with and what type of bacteria is it most effective against?
- answer cell wall synthesis; Gram positive due to the thick peptidoglycan layer
antimicrobial agents - answer kill or inhibit the growth of microorganisms
cidal agents - answer lethal to microorganisms
lytic agents - answer a type of cidal agent that lyses or breaks open cells
static agents - answer only inhibit the growth of microorganisms
T/F: If a static agent is removed, the microorganism will continue to grow. - answer true
disinfectants - answer antimicrobial agents for use on inanimate surfaces
examples of disinfectants - answer ammonia, ethanol, bleach, vesphene
antiseptics - answer antimicrobial agents that can be applied to skin but are not
necessarily safe for ingestion
examples of antiseptics - answer ethanol and iodine
antibiotics - answer antimicrobial chemotherapeutic agents of microbial origin used to
kill or inhibit the growth of bacteria - CAN BE TAKEN ORALLY OR THROUGH IV
examples of antibiotics - answer penicillin and streptomycin
Penicillin G is rarely used today due to what? - answer widespread antibiotic resistance
susceptible or sensitive - answer bacteria will not grow
what to look for when looking for sensitivity in a bacteria - answer zone of inhibition
mode of action - answer the way the agent kills or inhibits growth
mode of action for erythromycin and chloramphenicol - answer inhibits protein
synthesis by targeting the 50S subunit of the ribosome
Which antibiotic can affect the 50S subunit of the ribosome in bacteria along with the
70S subunit in humans? - answer chloramphenicol
,mode of action for gentamicin, tetracycline, and streptomycin - answer inhibits protein
synthesis by targeting the 30S subunit of the ribosome
streptomycin is only effective against: - answer Gram positive and Gram negative
bacteria that don't have a resistance mechanism against the antibiotic
Kirby-Bauer method - answer disc diffusion method in which different antimicrobial
agents are test where filter paper discs are saturated with agents that, over time, will
diffuse into the medium
zone of inhibition - answer clear area in which there is no bacterial growth
mechanisms of antibiotic resistance - answer 1. activate drug efflux pumps to push
antibiotic out of system
2. make enzymes to change or modify antibiotic
3. make enzymes to inactivate antibiotic
4. modify cell wall to keep antibiotic from entering
mode of action for cefoxitin and ampicillin - answer beta-lactams (like penicillin) -
inhibits cell wall synthesis
how to measure zone of inhibition - answer due to overlapping zones, measure radius
center until edge; multiply radius by 2 to get the diameter
FINAL ANSWER: the diameter in mm !!!
(ruler will be cm so multiply answer by 10 - move decimal point one place to the right)
Pseudomonas fluorescens - answer Gram negative
Resistant to chlorox (could be due to any of the 4 mechanisms of antibiotic resistance)
Sensitive to lysol, listerene, ethanol, H2O2, vesphene
Staphylococcus epidermidis (exp. 8) - answer Gram positive
Resistant to vesphene (could be due to any of the 4 mechanisms of antibiotic resistance)
Sensitive to H2O2, listerene, chlorox, ethanol, lysol
oxidase assay - answer tests for the presence of cytochrome c oxidase
*used to distinguish between genuses
substrate: oxygen
, product: water
reagent: tetramethyl-p-phenylenediamine dihydrochloride
media: TSA = trypticase soy agar
positive result: colony itself turns purple
positive example: Pseudomonas putida
negative result: colony stays white
negative example: Escherichia coli
Escherichia coli (exp. 9A) - answer oxidase negative, does not take up the dye in the
reagent and therefore does not change color to due to the absence of the cytochrome
oxidase enzyme
Pseudomonas putida (exp. 9A) - answer oxidase positive, takes up the purple dye in the
reagent due to the presence of the cytochrome oxidase enzyme
how to perform an oxidase test - answer TSA plate divided into thirds - transfer 200
microliters of the reagent tetramethyl-p-phenylenediamine dihydrochloride to each line
of bacteria
-the microorganism that produces the cytochrome oxidase enzyme will turn purple
where the reagent was added, whereas the oxidase negative will have no color change
indicating the absence of cytochrome oxidase
catalase assay - answer used to distinguish between genuses
*organisms that do aerobic respiration produce catalase, while organisms that are
strictly fermentative do not produce catalase
substrate: H2O2
product: water and oxygen
indicator: bubbles (production of oxygen)
positive result: production of bubbles when hydrogen peroxide is added
positive example: Staphylococcus epidermidis
negative result: no bubbles produced when hydrogen peroxide is added
negative example: Streptococcus mutans
ANSWERS 100% CORRECT
antibiosis - answer a symbiotic relationship between two organisms in which there is
inhibition, injury, or killing of one organism by another
what does penicillin interfere with and what type of bacteria is it most effective against?
- answer cell wall synthesis; Gram positive due to the thick peptidoglycan layer
antimicrobial agents - answer kill or inhibit the growth of microorganisms
cidal agents - answer lethal to microorganisms
lytic agents - answer a type of cidal agent that lyses or breaks open cells
static agents - answer only inhibit the growth of microorganisms
T/F: If a static agent is removed, the microorganism will continue to grow. - answer true
disinfectants - answer antimicrobial agents for use on inanimate surfaces
examples of disinfectants - answer ammonia, ethanol, bleach, vesphene
antiseptics - answer antimicrobial agents that can be applied to skin but are not
necessarily safe for ingestion
examples of antiseptics - answer ethanol and iodine
antibiotics - answer antimicrobial chemotherapeutic agents of microbial origin used to
kill or inhibit the growth of bacteria - CAN BE TAKEN ORALLY OR THROUGH IV
examples of antibiotics - answer penicillin and streptomycin
Penicillin G is rarely used today due to what? - answer widespread antibiotic resistance
susceptible or sensitive - answer bacteria will not grow
what to look for when looking for sensitivity in a bacteria - answer zone of inhibition
mode of action - answer the way the agent kills or inhibits growth
mode of action for erythromycin and chloramphenicol - answer inhibits protein
synthesis by targeting the 50S subunit of the ribosome
Which antibiotic can affect the 50S subunit of the ribosome in bacteria along with the
70S subunit in humans? - answer chloramphenicol
,mode of action for gentamicin, tetracycline, and streptomycin - answer inhibits protein
synthesis by targeting the 30S subunit of the ribosome
streptomycin is only effective against: - answer Gram positive and Gram negative
bacteria that don't have a resistance mechanism against the antibiotic
Kirby-Bauer method - answer disc diffusion method in which different antimicrobial
agents are test where filter paper discs are saturated with agents that, over time, will
diffuse into the medium
zone of inhibition - answer clear area in which there is no bacterial growth
mechanisms of antibiotic resistance - answer 1. activate drug efflux pumps to push
antibiotic out of system
2. make enzymes to change or modify antibiotic
3. make enzymes to inactivate antibiotic
4. modify cell wall to keep antibiotic from entering
mode of action for cefoxitin and ampicillin - answer beta-lactams (like penicillin) -
inhibits cell wall synthesis
how to measure zone of inhibition - answer due to overlapping zones, measure radius
center until edge; multiply radius by 2 to get the diameter
FINAL ANSWER: the diameter in mm !!!
(ruler will be cm so multiply answer by 10 - move decimal point one place to the right)
Pseudomonas fluorescens - answer Gram negative
Resistant to chlorox (could be due to any of the 4 mechanisms of antibiotic resistance)
Sensitive to lysol, listerene, ethanol, H2O2, vesphene
Staphylococcus epidermidis (exp. 8) - answer Gram positive
Resistant to vesphene (could be due to any of the 4 mechanisms of antibiotic resistance)
Sensitive to H2O2, listerene, chlorox, ethanol, lysol
oxidase assay - answer tests for the presence of cytochrome c oxidase
*used to distinguish between genuses
substrate: oxygen
, product: water
reagent: tetramethyl-p-phenylenediamine dihydrochloride
media: TSA = trypticase soy agar
positive result: colony itself turns purple
positive example: Pseudomonas putida
negative result: colony stays white
negative example: Escherichia coli
Escherichia coli (exp. 9A) - answer oxidase negative, does not take up the dye in the
reagent and therefore does not change color to due to the absence of the cytochrome
oxidase enzyme
Pseudomonas putida (exp. 9A) - answer oxidase positive, takes up the purple dye in the
reagent due to the presence of the cytochrome oxidase enzyme
how to perform an oxidase test - answer TSA plate divided into thirds - transfer 200
microliters of the reagent tetramethyl-p-phenylenediamine dihydrochloride to each line
of bacteria
-the microorganism that produces the cytochrome oxidase enzyme will turn purple
where the reagent was added, whereas the oxidase negative will have no color change
indicating the absence of cytochrome oxidase
catalase assay - answer used to distinguish between genuses
*organisms that do aerobic respiration produce catalase, while organisms that are
strictly fermentative do not produce catalase
substrate: H2O2
product: water and oxygen
indicator: bubbles (production of oxygen)
positive result: production of bubbles when hydrogen peroxide is added
positive example: Staphylococcus epidermidis
negative result: no bubbles produced when hydrogen peroxide is added
negative example: Streptococcus mutans
