gtc micro lab final ALL EXERCISES 15-20

how are zones of inhibition measured?

in millimeters

at what temperature are bacteria and tubes incubated at?

37 degrees C

what type of bacteria does our antibiotic sensitivity exercise test? (gram + or -)

both gram + and gram -

what range of microorganisms do broad spectrum antibiotics target?

a wide range; used when cause of infection is unknown

what range of microorganisms do narrow spectrum antibiotics target?

target one particular agent when cause of infection is known

define bacteriostatic antibiotics

antibiotics that inhibit/stop the GROWTH of bacteria

define bactericidal antibiotics

antibiotics that kill the bacteria

name 5 antibiotic modes of action

-inhibit cell wall

-interfere with 70s ribosome

-damage prokaryotic cell membrane

-interfere with nucleic acid synthesis

-block prokaryotic metabolism

why is it optimal to use a spread plate to test antibiotic sensitivity?

an even lawn of bacteria allows an accurate and measurable zone of inhibition to evaluate antibiotic sensitivity

which inoculating tool/transfer instrument do we use for antibiotic sensitivity testing to push the disc into the agar?

alcohol-flamed forceps

what is the purpose of the oxygen requirements experiment?

to classify bacteria based on their requirements for oxygen

name the 4 classifications for bacteria based on their oxygen requirements?

obligate aerobes, obligate anaerobes, facultative anaerobes, microaerophilic anaerobes

what type of bacteria require the prescence of oxygen to grow?

obligate aerobes

what type of bacteria cannot grow in the prescence of oxygen?

obligate anaerobes

what type of bacteria can only tolerate small amounts of oxygen?

microaerophilic anaerobes

what type of bacteria grow well in aerobic and anaerobic conditions?

facultative anaerobes

what type of inoculating tool/transfer tool will we use for the oxygen requirements experiment?

inoculating loop

these bacteria were placed into an aerobic environment. what can we conclude about the oxygen requirements of bacteria #1?

it is an obligate anaerobe

these bacteria were placed into an aerobic environment. what can we conclude about the oxygen requirements of bacteria #5?

it is a facultative anaerobe

these bacteria were placed into an aerobic environment. what can we conclude about the oxygen requirements of bacteria #9?

it is an obligate aerobe

these bacteria were placed into an anaerobic environment. what can we conclude about the oxygen requirements of bacteria #1?

it is an obligate anaerobe

these bacteria were placed into an anaerobic environment. what can we conclude about the oxygen requirements of bacteria #5?

it is a facultative anaerobe

these bacteria were placed into an anaerobic environment. what can we conclude about the oxygen requirements of bacteria #9?

it is an obligate aerobe

what is the purpose of selective media?

inhibits the growth of a specific group of microbes while allowing the growth of another specific group of microbes

what is the purpose of differential media?

differentiates between closely related organisms using differences in growth patterns/biochemical changes

what kind of test is a hemolysis test?

a differential test

what is the purpose of the hemolysis test?

determine what bacteria have the ability to breakdown Red Blood Cells

what species of bacteria is the hemolysis test used to differenciate?

Streptococcus species

what type of inoculating tool/transfer tool is used to perform the hemolysis test?

an inoculating loop

what will a blood agar plate look like if a bacteria incubated on it was beta hemolytic, and why?

a clear ring would be observed around the colonies, because beta hemolysis is the most aggressive

what will a blood agar plate look like if a bacteria incubated on it was alpha hemolytic, and why?

a green hue would be observed around the colonies, because these bacteria result in the discoloration of red blood cells to a green color instead of hemolysis

what will a blood agar plate look like if a bacteria incubated on it was gamma hemolytic?

no change on the blood agar

this bacteria was plated and incubated on a sheep blood agar. what type of hemolysis does #4 exhibit?

beta hemolysis

this bacteria was plated and incubated on a sheep blood agar. what type of hemolysis does #11 exhibit?

gamma hemolysis

what type of test is the MSA (mannitol/salt agar) test?

a selective AND differential test

how can the mannitol/salt agar test be selective and differential at the same time?

it allows gram POSITIVE salt-loving (halophiles) staphylococci to grow, but differentiates them based on their ability to ferment the sugar mannitol

what inoculating tool/transfer tool is used for the mannitol/salt agar test?

an inoculating loop

what is the PH indicator used for the mannitol/salt agar test?

phenol red

how will the mannitol/salt agar appear if the bacteria has positive mannitol fermentation?

it will appear yellow

how will the mannitol/salt agar appear if the bacteria has negative mannitol fermentation, but doesn't die?

reddish/pink color

what types of bacteria can grow on a mannitol/salt agar?

gram positive cocci

these bacteria were placed in a mannitol/salt agar. what can we conclude about #5?

it is positive for mannitol fermentation

these bacteria were placed in a mannitol/salt agar. what can we conclude about #3?

it is negative for mannitol fermentation

(since it grew, it must be a staphylococcus species)

these bacteria were placed in a mannitol/salt agar. what can we conclude about #6?

it is negative for mannitol fermentation

(since it did not grow, probably not a staph species)

what is the purpose of the Eosin Methylene Blue (EMB) test?

to differentiate between gram negative lactose/nonlactose fermenters

what type of bacteria does the Eosin Methylene Blue (EMB) Agar allow for the growth of?

gram negative lactose/nonlactose fermenters

how is the Eosin Methylene Blue Agar (EMB) selective and differential at the same time?

it inhibits the growth of gram positive bacteria and allows the growth of gram negative bacteria

what might an Eosin Methylene Blue (EMB) agar plate look like when it has a positive lactose fermenter result?

trail of colonies that are dark purple/pink and sometimes a green metallic color on top

what might an Eosin Methylene Blue (EMB) agar plate look like when it has a gram negative bacteria but no lactose fermenting properties

clear bacterial growth

which bacteria is most commonly known for producing dark purple/pink colonies and a green metallic color?

Escherichia Coli (E.Coli)

these bacteria have been plated and incubated on an EMB agar plate. what can we assume about #6?

it is a lactose fermenting gram-negative bacteria

these bacteria have been plated and incubated on an EMB agar plate. what can we assume about #12?

it is a non-lactose fermenting gram-negative bacteria

these bacteria have been plated and incubated on an EMB agar plate. what can we assume about #3?

it is not a gram negative bacteria

what inoculating tool/transfer tool is used to perform the Eosin Methylene Blue Agar (EMB) test?

an inoculating loop

the presence of what molecule allows the EMB agar to be a differential medium?

lactose

what type of bacteria posess the cytochrome c OXIDASE enzyme

only obligate aerobes (not even facultative anaerobes)

what is the purpose of the oxidase test?

to classify a bacteria's tolerance to air

what is the function of the cytochrome oxidase?

acts as an electron carrier in a set of electron carriers called cytochromes

what bacteria is the oxidase test generally used to differenciate?

pseudomonadaceae or enterobacteriaceae

what inoculating tool/transfer tool is used for the oxidase test?

the wooden end of a cotton swab

what can be assumed about the bacteria on side A?

they contain the cytochrome C oxidase enzyme, meaning they are obligate aerobes

what can be assumed about the bacteria on side B?

they do not contain the cytochrome C oxidase enzyme, meaning they are anaerobic

what is the purpose of the catalase test?

identify bacteria that carry the enzyme catalase & are obligate aerobes

what term describes bacteria that produce oxygen + bubbles in the presence of hydrogen peroxide?

catalase positive

what does a positive catalase test indicate about a bacteria?

it is an obligate aerobe

what inoculating tool/transfer tool is used for the catalase test?

the wooden end of a cotton swab

what is the formula that describes the breakdown of hydrogen peroxide with catalase?

2H2O2 -> 2H2O + O2

how would you describe bacterium A?

catalase negative

what is the purpose of the amylase test?

determine wether a bacterium produces amylase, an enzyme that breaks down starch

after incubation, which solution will be added into a starch agar plate to determine the prescence of amylase?

Lugol's Iodine

what would a starch agar plate look like in the presence of amylase?

it would produce a clearing under the bacteria, meaning its amylase broke down the starch

what would a starch agar plate look like in the absence of amylase?

it will turn dark brown/black (iodine solution will cause the color change)

these bacteria were inoculated on a starch agar plate. what can be assumed about the enzyme bacteria A produced?

it produced amylase and broke down the starch in the agar plate

which bacteria is amylase positive?

bacteria A

which bacteria is amylase negative?

bacteria B

what is the purpose of the urease agar test?

determine if a bacteria can break down urea and survive acidic environments

what is the name of the PH indicator that is present in the urease agar test?

Phenol Red

what inoculating tool/transfer tool is used for the urease agar test?

inoculating needle for stab and streak technique

what color does the PH indicator phenol red turn at alkaline PHs?

red/pink

what color does the PH indicator phenol red turn at acidic PHs?

yellow

what color would a urea broth turn in the presence of urease activity, and why?

a red/pink color, indicating the breakdown of Urea into ammonia (a base)

what color would a urea broth turn in the absence of urease activity, and why?

it would remain yellow orange, indicating a negative urease test

these bacteria were placed in a urea agar tube. what can be concluded about tube A?

it is urease positive, meaning it broke urea down into ammonia

these bacteria were placed in a urea agar tube. what can be concluded about tube B?

it is urease negative, meaning it did not break urea down into ammonia

what type of test is the lethicinase test?

a differential test

how is the lethicinase test differential?

it differentiates between two gram positive bacillus-shaped bacteria that can be difficult to tell apart

what inoculating tool/transfer tool is used for the lethicinase test?

an inoculating loop

what type of agar is used to determine wether or not a bacteria has lethicinase, and why?

mannitol egg yolk polymyxin (MYP) agar

Egg yolk: detects lecithinase

Polymyxin: inhibits many other bacteria, separating gram positive bacilli

Mannitol: tests carbohydrate source of the media

what would an MYP agar look like in the presence of lethicinase?

white/pink precipitate around colonies

what would an MYP agar look like in the absence of lethicinase, and why?

yellow precipitate around colonies due to the fermentation of the mannitol present in the agar

these bacteria were inoculated onto a Mannitol egg yolk polymyxin (MYP) agar. what can be concluded about bacteria A?

they are lethicinase positive and broke down the egg yolk component of the agar

these bacteria were inoculated onto a Mannitol egg yolk polymyxin (MYP) agar. what can be concluded about bacteria B?

they are lethicinase negative, but fermented the agar's mannitol, producing a yellow precipitate

what is the purpose of the triple sugar iron (TSI) test?

to identify bacteria that can ferment carbohydrates and produce hydrogen sulfide

what is the PH indicator involved in the TSI agar test?

phenol red

what inoculating tool/transfer tool is used for the TSI agar test?

an inoculating needle to use the stab and streak technique

what type of bacteria is TSI agar used to differentiate?

gram-negative rod shaped bacteria based on sugar fermentation and hydrogen sulfide production

what color would a TSI agar test look like if the bacteria fermented one or more of the carbohydrates, but does not combine with iron to produce hydrogen sulfide?

the media would turn yellow

what color would a TSI agar test look like if the bacteria fermented one or more of the carbohydrates and produces hydrogen sulfide?

the media would turn yellow and black

what color would a TSI agar test look like if the bacteria did not ferment any of the carbohydrates, and did not produce hydrogen sulfide?

the media would stay red

what color would a TSI agar test look like if the bacteria did not ferment any of the carbohydrates, but combined with iron to produce hydrogen sulfide?

the media would turn black