Microbiology Lab 2 Exam

Which bacteria is able to successfully digest starch present in the agar? a) Bc b) Ec c) Ss d) Ef

a) Bc We can see evidence of starch digestion where Bc is streaked since the iodine did not react with the agar plate.

What is the action of amylase? a) It is an enzyme that can break down starch for organisms to use to make energy. b) It can combine smaller carbohydrates into bigger chains like starch. c) It can break down protein chains, giving the bacteria food. d) It can build protein chains to make the bacteria stronger.

a) It is an enzyme that can break down starch for organisms to use to make energy. *Amylase has the capability to break down starch into smaller disaccharides that are easier to digest.

Select all of the following organisms that would be oxidase positive. a) Neisseria b) E. coli c) Bacillus d) P. aeruginosa

a) Neisseria c) Bacillus d) P. aeruginosa

What would a strong positive result on an EMB plate indicate? a) Someone did not wash their hands after using the bathroom. b) Someone has an active MRSA infection. c) Someone has Enterococcus faecalis as part of their own microbiome. d) Someone sneezed in their hands.

a) Someone did not wash their hands after using the bathroom. *A strong positive on an EMB plate would show a gram-negative enteric bacteria, which is associated with people not washing their hands post bathroom use. This is most usually associated with food poisoning.

Which of these organisms is definitely amylase positive on the starch test? a) E. coli b) E. aerogenes c) B. cereus d) Klebsiella pneumoniae

c) B. cereus *We know that B. cereus is amylase positive because we used it on our starch plates and found evidence of starch break down.

The Thioglycolate tube shown here is what type of organism? (image shows the entire tube is turbid/cloudy, ring at the top) a) Obligate anaerobe b) Obligate aerobe c) Facultative anaerobe d) Microaerophile

c) Facultative anaerobe *Facultative anaerobes have the ability to grow in the oxic zone and below it as well.

The oxidase test is useful for distinguishing between which organisms? a) Gram positive cocci. b) Gram negative cocci. c) Gram negative rods. d) Gram positive rods.

c) Gram negative rods.

The catalase test is useful in distinguishing what strains of bacteria from one another? a) Gram negative cocci, especially Micrococcus species. b) Gram positive bacilli, especially Pseudomonas. c) Gram positive cocci, especially Staph and Strep. d) Gram positive bacilli, especially E. coli.

c) Gram positive cocci, especially Staph and Strep.

Match the type of bacteria with the hemolytic characteristics they exhibit. Bacteria: -Beta hemolysis. -Alpha hemolysis. -Gamma hemolysis. Characteristics: -Enterococcus faecalis -Streptococcus pyogenes -Streptococcus sanguinis

Beta hemolysis: Streptococcus pyogenes Alpha hemolysis: Streptococcus sanguinis Gamma hemolysis: Enterococcus faecalis

Match the definitions of each type of hemolysis. Hemolysis Type: -Beta hemolysis -Alpha hemolysis -Gamma hemolysis Definition: -Partial RBC destruction, will create green halo around bacterial growth. -No RBC destruction at all. -Complete RBC destruction.

Beta hemolysis: complete RBC destruction. Alpha hemolysis: partial RBC destruction, will create green halo around bacterial growth. Gamma hemolysis: no RBC destruction at all.

Match the category of aerotolerance with the definition. Category: -Obligate aerobes -Facultative anaerobes -Obligate anaerobes -Microaerophiles -Aerotolerant anaerobes Definition: -Unable to grow in the presence of oxygen -Rely on oxygen for aerobic respiration -Don't use oxygen, but can tolerate it and will be able to grow in its presence -Use oxygen but in little amount, too much will the bacteria -Use oxygen for aerobic respiration, but can also make ATP without it

Obligate aerobes: Rely on oxygen for aerobic respiration Facultative anaerobes: Use oxygen for aerobic respiration, but can also make ATP without it Obligate anaerobes: Unable to grow in the presence of oxygen Microaerophiles: Use oxygen but in little amount, too much will the bacteria Aerotolerant anaerobes: Don't use oxygen, but can tolerate it and will be able to grow in its presence *Obligate aerobes need oxygen to survive. Facultative anaerobes can survive in both environments. Obligate anaerobes require a zero oxygen environment. Microaerophiles only use a small amount of oxygen and too much will kill them. Aerotolerant anaerobes can survive in an environment with oxygen but they will not use it.

Select both the selective and differential properties of the EMB agar. -Selective: Will select against gram positive organisms because of the eosin methylene blue dye in the agar. -Selective: Will select against gram negative organisms because of the methylene blue dye in the agar. -Differential: The bacteria will change the color of the agar depending on its ability to ferment mannitol. -Differential: The bacteria will change the color of the agar depending on its ability to ferment lactose and to what degree it can ferment the sugar.

Selective: Will select against gram positive organisms because of the eosin methylene blue dye in the agar. Differential: The bacteria will change the color of the agar depending on its ability to ferment lactose and to what degree it can ferment the sugar.

Match the characteristics of the bacteria with how they would grow and appear on an EMB plate. Bacteria: -Strong lactose fermenter. -Weak lactose fermenter. -Gram-positive bacteria. -Non-lactose fermenting gram-negatives. Characteristics: -Growth will be inhibited by the dye. -Growth will appear bubblegum pink. -Growth will appear clear. -Growth will appear metallic green.

Strong lactose fermenter: growth will appear metallic green. Weak lactose fermenter: growth will appear bubblegum pink. Gram-positive bacteria: growth will be inhibited by the dye. Non-lactose fermenting gram-negatives: growth will appear clear.

Which bacteria from last week exhibited this pattern of growth in the Thioglycolate broth? (broth is clear and has a pink ring at the top) a) Alcaligenes faecalis b) Clostridium sporogenes c) Escherichia coli d) Micrococcus luteus

a) Alcaligenes faecalis *Af is an obligate aerobe and will only grow in the oxic (pink) zone.

What type of hemolysis is shown here? (image shows green/brown streak with a halo around the growth on the blood agar) a) Alpha b) Beta c) Gamma d) None

a) Alpha *This is alpha hemolysis. Alpha is partial break down of RBC's, which creates a green/brown halo around the bacterial growth.

S. pyogenes is a member of the group clinically known as? a) Group D Alpha Hemolytic Strep (GDAHS) b) Group A Beta Hemolytic Strep (GABHS) c) Group A Alpha Hemolytic Strep (GAAHS) d) None of the above.

b) Group A Beta Hemolytic Strep (GABHS)

Which of the species below should differentially turn the MSA agar from pink to yellow? a) Staphylococcus epidermidis. b) Staphylococcus aureus. c) Escherichia coli. d) Micrococcus luteus.

b) Staphylococcus aureus. *S. aureus is able to grow since it is a gram positive organism and it can ferment the mannitol, creating the acid by-product and lowering the pH.

Why are hemolysins associated with pathogenicity? a) They break down WBC's. b) They break down RBC's. c) They break down platelets.

b) They break down RBC's. *Hemolysins break down RBC's, which can lead to a variety of complications, such as anemia.

What would be the correct statement about a Phenol Red Broth result that turned yellow and has an air bubble? a) It produced acid and no gas: +/- b) It did not produce acid, but it did produce gas: -/+ c) It produced both acid and gas: +/+ d) It did not produce acid or gas: -/-

c) It produced both acid and gas: +/+ *This bacteria was able to ferment the lactose, lowering the pH and changing the color to yellow. It also produced gas as a by-product of the fermentation, which we can see in the Durham tube.

Which of the following bacteria should not be able to grow on the MSA plates? a) Staphylococcus aureus. b) Staphylococcus epidermidis. c) Pseudomonas aeruginosa. d) Micrococcus luteus.

c) Pseudomonas aeruginosa. *Gram-negative bacteria, like P. aeruginosa, will not be able to grow on MSA plates.

What does this aerobic plate tell you about Clostridium sporogenes? (image shows no growth of Cs, but growth of Af, Bc, and Ec) a) That it is an obligate aerobe. b) That it is a microaerophile. c) That it is an obligate anaerobe. d) That it is a facultative anaerobe.

c) That it is an obligate anaerobe. *Obligate anaerobes cannot grow in the presence of oxygen.

What is the selective property of the MSA plate? a) The mannitol sugar in the agar selects for the growth of Staph species. b) The salt in the agar allows Staph species to turn the agar from red to yellow. c) The high sodium content of the MSA plate inhibits the growth of gram-negative bacteria, and only selects for gram-positive bacteria that are halophiles. d) The mannitol in the agar selects against gram-positive bacterias.

c) The high sodium content of the MSA plate inhibits the growth of gram-negative bacteria, and only selects for gram-positive bacteria that are halophiles. *The high salt content on the agar selects against gram-negative species, only allowing gram-positive species to grow.

What is the purpose of pouring iodine over the starch plate? a) The iodine will react where the starch was digested to create a dark purple color, but where the starch was not digested there will be no reaction and you will be able to see through the plate. b) The iodine makes it easier to see the bacteria on the plate. c) The iodine will react with the starch in the agar plate to create a dark purple color, but if the starch was digested then no reaction will occur and you will be able to see through the plate. d) The iodine reacts with the bacteria to create a dark purple color if the bacteria produces the enzyme amylase.

c) The iodine will react with the starch in the agar plate to create a dark purple color, but if the starch was digested then no reaction will occur and you will be able to see through the plate. *The iodine will react with the starch creating a dark purple color. But, if the starch was digested then you will be able to see through the plate since no reaction between the iodine and starch will occur.

What was the purpose of streaking the five bacteria on the TSA plate? a) This was used to practice aseptic technique and streaking again. b) This was used to use up more of the bacterial broth cultures. c) This was used as a control to see how the bacteria would grow on a plate with no selective or differential properties. d) This was used to show the difference in the color of agars before inoculation.

c) This was used as a control to see how the bacteria would grow on a plate with no selective or differential properties.

What type of growth is indicated by this Thioglycolate tube? (image shows no growth at the top of the tube and growth throughout the rest of the tube) a) Obligate aerobe. b) Aerotolerant anaerobe. c) Facultative anaerobe. d) Obligate anaerobe.

d) Obligate anaerobe. *The growth is only in the anoxic zone.

If there is suspected fecal coliform contamination of romaine lettuce at a restaurant, which of these tests is presumptive and would be the first one done? a) EMB agar plate. b) MSA plate. c) TSA plate. d) Phenol Red Broth with Durham Tube test.

d) Phenol Red Broth with Durham Tube test. *The presumptive test would be looking for gas production as a by-product of sugar fermentation. After we see gas production we would move on to an EMB agar plate, which is the confirmatory test.

What are we looking for when we do the Coagulase (Staphyloslide) test? a) We are looking for the bacteria's ability to ferment sugars. b) We are looking for Cytochrome C Oxidase protein in the bacterial c) We are looking for the catalase enzyme that neutralizes hydrogen peroxide. d) We are looking for agglutination by the coagulase enzyme produced by S. auerus.

d) We are looking for agglutination by the coagulase enzyme produced by S. auerus. *We are looking for the enzyme coagulase that produces clots by activating fibrinogen.