Quiz 2 Flashcards
What is the purpose of the endospore stain?
to stain and visualize endospores and differentiate spore forming cells from non-spore forming cells (a differential stain)
When do endospores form?
in harsh conditions (i.e temperature changes, changes in pH, dehydration, UV, nutrient loss, or oxygen concentrations)
What are endospores made of?
a tough keratin protein
What is an example organism of an endospore?
bacillus anthracis - causes anthrax
What are the two genus that are most likely to contain endospores?
bacillus (aerobic) and clostridium (anaerobic)
both of which are gram positive bacteria
Why do you need to steam the stain when you apply malachite green in an endospore stain?
you need to steam in order to get the dye into the tough keratin of the endospore
What color is the spore producing bacteria and non-spore producing bacteria after the decolorization process?
the spore producer is green
nonspore producer is clear
What is the purpose of the acid fast stain?
to stain acid fast bacterial cell walls and differentiate acid fast bacteria from non-acid fast bacteria
What organisms are acid fast positive and what is their cell wall mostly made of?
organisms with mycobacterium
they have a cell wall made of 60% mycolic acid
What is the purpose of having a mycolic acid cell wall?
works as a sticky/waxy adherence factor that protects from phagocytic digestion, dehydration, and chemicals
What dye do we need to steam with an acid fast stain?
carbbofushin to penetrate the waxy mycolic acid
What is the counterstain used in an acid fast stain?
methyl blue
What color will acid fast positive and negative bacteria be before and after the decolorization process?
acid fast positive bacteria will be pink after decolorization and acid fast negative will be blue
both will be pink before decolorization
What is an example of bacteria for an acid fast stain?
mycobacterium tuberculosis - causes lung tuberculosis
What is the purpose of the phenol red test?
to determine if bacteria can metabolize a specific carbohydrate
What is the purpose of the derm tube within the test tube?
to determine whether or not gas was produced as some bacteria
Why are peptones included within the phenol red broth?
food for general bacterial growth
Why is sodium chloride included within the phenol red broth?
for salt balance
Why does carbohydrate need to be included within the phenol red broth?
it is the substrate that we are testing for metabolism of a carbohydrate
What is phenol red within the phenol red test and what does its resulting color indicate?
It works as a pH indicator
yellow = acidic
red/orange = neutral
magenta/pink = alkaline
What are the products being recorded during the phenol red broth test?
acids, alcohols, and + or - gases
What would a yellow test with turbidity indicate in the phenol red broth?
an acidic positive metabolism of sugar (with or without gases)
What would a red/pink test with turbidity indicate in the phenol red broth?
an alkaline negative metabolism of sugar as it uses peptones as a food source
Why does the readout of a phenol red broth test be done between 24 and 48 hours after inoculation?
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
What does it mean to be a non-saccharolytic?
does not metabolize sugar but rather uses protein as a food source
What is the purpose of the oxidation/fermentation test?
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”
What was the media that was used for the OF test and how did we collect from the media?
it was an agar deep and we did a stab inoculation with a needle
What was the purpose of the mineral oil in the OF test?
mineral oil is used to seal out oxygen in the anaerobic tube while the tube without mineral oil is testing for oxidation
What is the purpose of a buffer in the OF test?
to keep the pH constant
What is the purpose of the agar in the OF test?
works as a thickening agent to determine the motility and excludes oxygen for the fermentation tube
What was the pH indicator used in the OF test and what do the resulting colors mean?
bromothymol blue
yellow = acidic
green = neutral
blue = alkaline
Why was glucose included in the OF test?
works as a substrate for fermentation or oxidation
What are the products of the aerobic tube in the OF test?
acids
What are the products of the anaerobic tube in the OF test?
acids, alcohol, and +/- gases
What is a facultative anaerobe?
grows better with or without oxygen. but grows better with oxygen
What are the media within the IMViC tubes that we made?
MRVP broth
Tryptone broth
Citrate slant
- zig zag inoculated with a needle to not transfer too much bacteria
What do the letters IMVC stand for?
I = indole
M = methyl red
V = voges proskauer
C = citrate
What is the media used for a MRVP, indole, and citrate tube?
MRVP broth
Tryptone broth
Citrate slant
What is the purpose of the indole production test?
to determine whether bacteria can produce indole from tryptophan (an amino acid)
What is the substrate, endoenzymes, and products being recorder in the biochemical sheet for the indole production test?
substrate = tryptophan
endoenzyme = tryptophanase
products = pyruvate, ammonia, and indole
Why can’t we use a pH indicator in the indole production test?
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
What is the reagent being used in the indole production test and what does it do?
kovac’s reagent
it detects the presence of indole
What colors does kovac’s reagent produce in a positive and negative test of indole in a indole production test?
yellow = negative (no indole produced)
pink = positive (indole is present)
What is the purpose of the methyl red and voges proskauer test?
to determine whether bacteria ferment glucose into mixed acids or acetoin
What is the substrate, endoenzymes, and products being recorded in the biochemical sheet for the methyl red production test?
substrate = glucose
endoenzymes = various enzymes
products = stable mixed acids (decrease the pH)
What is the substrate, endoenzymes, and products being recorded in the biochemical sheet for the voges proskauer production test?
substrate = glucose
endoenzymes = various enzymes
products = acetoin (increases the pH)
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?
both methyl red and this happens if the pH decreases
Why can’t we do the read out for VP for 24 hours?
acids will be produced and acetoin will be produced after 48 hours which is the product that will be detected in the VP test
What are the reagents used in the VP test and why does it turn pink/red if it shows a positive test?
VPA and VPB and it turns pink/red if acetoin is present
Why are organisms that are MR+ usually VP-, and VP+ organisms usually MR-?
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)
What is the purpose of the citrate utilization test?
to determine whether bacteria can utilize citrate as a sole carbon source
Why do we add citrate to the media in a citrate test?
it is our sole source of carbon and organisms need carbon to make all macromolecules
Why do we include ammonium dihydrogen phosphate in the recipe for the citrate utilization test?
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
What is the pH indicator used in the citrate utilization test and what are the results of its colors produced?
bromothymol blue
yellow = acidic
green = neutral
blue = alkaline
What are the substrates. endoenzymes, and products being recorded in the biochemical sheet for the citrate utilization test?
substrate = citrate and ammonium phosphate
endoenzymes = citrate permease
products = ammonia and ammonium hydroxide
What does a positive and negative test look like for a citrate utilization test?
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)
What is agar?
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)
At what temperature does agar liquify and solidify?
liquefies at 100 degrees Celsius and solidifies at 40 degrees Celsius
What is chemically defined media and what is it used for?
exact chemical composition is known
it is used for fastidious organisms, those that require many growth factors provided in chemically defined media
