Quiz 2

Question 1

What is the purpose of the endospore stain?

Answer 1

to stain and visualize endospores and differentiate spore forming cells from non-spore forming cells (a differential stain)

Question 2

When do endospores form?

Answer 2

in harsh conditions (i.e temperature changes, changes in pH, dehydration, UV, nutrient loss, or oxygen concentrations)

Question 3

What are endospores made of?

Answer 3

a tough keratin protein

Question 4

What is an example organism of an endospore?

Answer 4

bacillus anthracis - causes anthrax

Question 5

What are the two genus that are most likely to contain endospores?

Answer 5

bacillus (aerobic) and clostridium (anaerobic)
both of which are gram positive bacteria

Question 6

Why do you need to steam the stain when you apply malachite green in an endospore stain?

Answer 6

you need to steam in order to get the dye into the tough keratin of the endospore

Question 7

What color is the spore producing bacteria and non-spore producing bacteria after the decolorization process?

Answer 7

the spore producer is green

nonspore producer is clear

Question 8

What is the purpose of the acid fast stain?

Answer 8

to stain acid fast bacterial cell walls and differentiate acid fast bacteria from non-acid fast bacteria

Question 9

What organisms are acid fast positive and what is their cell wall mostly made of?

Answer 9

organisms with mycobacterium

they have a cell wall made of 60% mycolic acid

Question 10

What is the purpose of having a mycolic acid cell wall?

Answer 10

works as a sticky/waxy adherence factor that protects from phagocytic digestion, dehydration, and chemicals

Question 11

What dye do we need to steam with an acid fast stain?

Answer 11

carbbofushin to penetrate the waxy mycolic acid

Question 12

What is the counterstain used in an acid fast stain?

Answer 12

methyl blue

Question 13

What color will acid fast positive and negative bacteria be before and after the decolorization process?

Answer 13

acid fast positive bacteria will be pink after decolorization and acid fast negative will be blue

both will be pink before decolorization

Question 14

What is an example of bacteria for an acid fast stain?

Answer 14

mycobacterium tuberculosis - causes lung tuberculosis

Question 15

What is the purpose of the phenol red test?

Answer 15

to determine if bacteria can metabolize a specific carbohydrate

Question 16

What is the purpose of the derm tube within the test tube?

Answer 16

to determine whether or not gas was produced as some bacteria

Question 17

Why are peptones included within the phenol red broth?

Answer 17

food for general bacterial growth

Question 18

Why is sodium chloride included within the phenol red broth?

Answer 18

for salt balance

Question 19

Why does carbohydrate need to be included within the phenol red broth?

Answer 19

it is the substrate that we are testing for metabolism of a carbohydrate

Question 20

What is phenol red within the phenol red test and what does its resulting color indicate?

Answer 20

It works as a pH indicator

yellow = acidic
red/orange = neutral
magenta/pink = alkaline

Question 21

What are the products being recorded during the phenol red broth test?

Answer 21

acids, alcohols, and + or - gases

Question 22

What would a yellow test with turbidity indicate in the phenol red broth?

Answer 22

an acidic positive metabolism of sugar (with or without gases)

Question 23

What would a red/pink test with turbidity indicate in the phenol red broth?

Answer 23

an alkaline negative metabolism of sugar as it uses peptones as a food source

Question 24

Why does the readout of a phenol red broth test be done between 24 and 48 hours after inoculation?

Answer 24

when bacteria are given the choice between proteins or sugars, if they metabolize sugars, they will digest sugars first but the sugar begins to run out and then bacteria has no choice but to digest remaining peptones so test will produce an alkaline product causing a pH reversion

Question 25

What does it mean to be a non-saccharolytic?

Answer 25

does not metabolize sugar but rather uses protein as a food source

Question 26

What is the purpose of the oxidation/fermentation test?

Answer 26

determining whether bacteria oxidize and/or ferment glucose "whether they metabolize glucose and whether or not it is in the presence of oxygen or in the absence of oxygen"

Question 27

What was the media that was used for the OF test and how did we collect from the media?

Answer 27

it was an agar deep and we did a stab inoculation with a needle

Question 28

What was the purpose of the mineral oil in the OF test?

Answer 28

mineral oil is used to seal out oxygen in the anaerobic tube while the tube without mineral oil is testing for oxidation

Question 29

What is the purpose of a buffer in the OF test?

Answer 29

to keep the pH constant

Question 30

What is the purpose of the agar in the OF test?

Answer 30

works as a thickening agent to determine the motility and excludes oxygen for the fermentation tube

Question 31

What was the pH indicator used in the OF test and what do the resulting colors mean?

Answer 31

bromothymol blue yellow = acidic green = neutral blue = alkaline

Question 32

Why was glucose included in the OF test?

Answer 32

works as a substrate for fermentation or oxidation

Question 33

What are the products of the aerobic tube in the OF test?

Answer 33

acids

Question 34

What are the products of the anaerobic tube in the OF test?

Answer 34

acids, alcohol, and +/- gases

Question 35

What is a facultative anaerobe?

Answer 35

grows better with or without oxygen. but grows better with oxygen

Question 36

What are the media within the IMViC tubes that we made?

Answer 36

MRVP broth Tryptone broth Citrate slant - zig zag inoculated with a needle to not transfer too much bacteria

Question 37

What do the letters IMVC stand for?

Answer 37

I = indole M = methyl red V = voges proskauer C = citrate

Question 38

What is the media used for a MRVP, indole, and citrate tube?

Answer 38

MRVP broth Tryptone broth Citrate slant

Question 39

What is the purpose of the indole production test?

Answer 39

to determine whether bacteria can produce indole from tryptophan (an amino acid)

Question 40

What is the substrate, endoenzymes, and products being recorder in the biochemical sheet for the indole production test?

Answer 40

substrate = tryptophan endoenzyme = tryptophanase products = pyruvate, ammonia, and indole

Question 41

Why can't we use a pH indicator in the indole production test?

Answer 41

ammonia is a base and pyruvate is an acid so they cancel each other out and won't be able to test for a change in pH

Question 42

What is the reagent being used in the indole production test and what does it do?

Answer 42

kovac's reagent it detects the presence of indole

Question 43

What colors does kovac's reagent produce in a positive and negative test of indole in a indole production test?

Answer 43

yellow = negative (no indole produced) pink = positive (indole is present)

Question 44

What is the purpose of the methyl red and voges proskauer test?

Answer 44

to determine whether bacteria ferment glucose into mixed acids or acetoin

Question 45

What is the substrate, endoenzymes, and products being recorded in the biochemical sheet for the methyl red production test?

Answer 45

substrate = glucose endoenzymes = various enzymes products = stable mixed acids (decrease the pH)

Question 46

What is the substrate, endoenzymes, and products being recorded in the biochemical sheet for the voges proskauer production test?

Answer 46

substrate = glucose endoenzymes = various enzymes products = acetoin (increases the pH)

Question 47

What is the pH indicator and reagent of the methyl red test and why does it turn pink/red if it shows a positive test?

Answer 47

both methyl red and this happens if the pH decreases

Question 48

Why can't we do the read out for VP for 24 hours?

Answer 48

acids will be produced and acetoin will be produced after 48 hours which is the product that will be detected in the VP test

Question 49

What are the reagents used in the VP test and why does it turn pink/red if it shows a positive test?

Answer 49

VPA and VPB and it turns pink/red if acetoin is present

Question 50

Why are organisms that are MR+ usually VP-, and VP+ organisms usually MR-?

Answer 50

if an organism is VP+, then it means that they produce acetoin, which raises the pH. Therefore it shouldn't test positive for MR too (which detects a low pH)

Question 51

What is the purpose of the citrate utilization test?

Answer 51

to determine whether bacteria can utilize citrate as a sole carbon source

Question 52

Why do we add citrate to the media in a citrate test?

Answer 52

it is our sole source of carbon and organisms need carbon to make all macromolecules

Question 53

Why do we include ammonium dihydrogen phosphate in the recipe for the citrate utilization test?

Answer 53

it is a source of nitrogen which means if organism can use citrate as a sole carbon source, they will also need nitrogen to break down the ammonium phosphate into basic products

Question 54

What is the pH indicator used in the citrate utilization test and what are the results of its colors produced?

Answer 54

bromothymol blue yellow = acidic green = neutral blue = alkaline

Question 55

What are the substrates. endoenzymes, and products being recorded in the biochemical sheet for the citrate utilization test?

Answer 55

substrate = citrate and ammonium phosphate endoenzymes = citrate permease products = ammonia and ammonium hydroxide

Question 56

What does a positive and negative test look like for a citrate utilization test?

Answer 56

positive = blue (even a small amount) or green with growth (bacteria only grows if they can use citrate) negative = green with no growth (bacteria only grows if they can use citrate)

Question 57

What is agar?

Answer 57

a complex polysaccharide that is used as a solidifying agent for culture media it is generally not metabolized by microbes (sugar that can't be digested)

Question 58

At what temperature does agar liquify and solidify?

Answer 58

liquefies at 100 degrees Celsius and solidifies at 40 degrees Celsius

Question 59

What is chemically defined media and what is it used for?

Answer 59

exact chemical composition is known it is used for fastidious organisms, those that require many growth factors provided in chemically defined media