Final Prep for Exam 1 Flashcards
Acid-fast bacterial cell walls are produced by the genus __________________________. Two diseases caused by this genus include ________________________ and __________________________.
3-8 Acid-Fast Stain
- Mycobacterium
- Lung tuberculosis
- Leprosy
Acid-fast cell walls are primarily made of ____________________ _________. Consequently, these cells are sticky and waxy.
3-8 Acid-Fast Stain
- 60% mycolic acid
Describe how acid-fast bacteria can to survive for longer in their environment. Give at least 3 ways.
3-8 Acid-Fast Stain
- Adherence factor
- Protection against phagocytic digestion
- Protects against dehydration
- Chemical protection (antibiotics and disinfectants)
Describe why carbolfuchsin dye must be heated and steamed during the acid-fast staining procedure.
3-8 Acid-Fast Stain
- Carbolfuchsin is lipid soluble and penetrates the waxy cell wall when steamed as outer surface is softened
After the acid-fast staining procedure, acid-fast cells will have the color ____________________ while non-acid-fast cells will have the color _____________________.
3-8 Acid-Fast Stain
- Pink
- Blue
During the last step of the acid-fast staining procedure, methylene blue is applied for 1 minute and then rinsed off. Explain why only some cells absorb the blue dye.
3-8 Acid-Fast Stain
- Acid-Fast positive cells have mycolic acid layer that can resist methylene blue staining.
When working with acid-fast bacteria, an inoculating ________________ (rather than a needle) should be used to obtain and mix the bacteria into an emulsion during the smear preparation. Why is this important?
3-8 Acid-Fast Stain
- Loop
- Becuase mycobacterium is sticky and would be hard to get on the stain with a needle
The non-pathogenic acid-fast genus and species of bacterium used in this experiment is called __________________ ____________________ and may cause an odor on the skin referred to as _________________ when it overgrows or is not washed by regular bathing.
3-8 Acid-Fast Stain
- Mycobacterium smegmatis
- Smegma
_________________________ _________________________. Although it does not cause disease, it does cause a condition called _____________________ when it overgrows on human skin.
3-8 Acid-Fast Stain
- Mycobacterium smegmatis
- Panniculitis
All fermentation pathways start with the compound ____________________, produced by _______________________. (process)
5-4 Methyl Red and Voges-Proskauer Test
- Pyruvate
- Glycolysis
The only carbon-containing compound in citrate medium is ______________________. Why do organisms need a carbon source?
5-9 Citrate Test
- Citrate
- To make all macro molecules
The only nitrogen source in citrate medium is ________________________. Why do organisms need a nitrogen source (to make which 2 macromolecules)?
5-9 Citrate Test
- Ammonium dihydrogen phosphate
- Amino acids and nucleotides (DNA, RNA)
In a medium where citrate is the only available carbon source, bacteria that possess the enzyme ________________________________ can transport the citrate molecules into the cell and metabolize them.
5-9 Citrate Test
- Citrate Permease
The pH indicator in citrate medium, bromothymol blue, is _________________ at pH 6.9 and ________________ at pH 7.6.
5-9 Citrate Test
- Green
- Blue
Bacteria that survive in this medium and utilize the citrate create an _____________________ (increase or decrease?) in the pH of the medium.
5-9 Citrate Test
- Increase
Describe a positive result in this medium. Why does the pH indicator in the medium change color in a positive test? Indicate the name of the product and the relative pH (acidic or basic) that caused the color change.
5-9 Citrate Test
- Positive test shows utilization of citrate through breakdown of Ammonium dihydrogen phosphate which causes increase in pH leading to blue color change
Describe a negative result in this medium. Why is there no growth in a negative result?
5-9 Citrate Test
- Negative is green with no growth. if it is green with growth it is still positive as there likely has not been enough alkaline products produced yet
- There will be no growth as citrate could not be utilized and no alkaline products were produced
If there is growth on citrate medium after incubation but no color change, this is considered a ________________________ result.
5-9 Citrate Test
Positive
Citrate utilization is one part of a test series referred to as IMViC; these letters stand for the 4 tests:
5-9 Citrate Test
I: Indole
M: Methyl Red
Vi: Voges-Prskauer
C: Citrate
The presence of ammonium hydroxide in the medium is INDIRECT evidence that the bacterium has broken down __________.
5-9 Citrate Test
- Citrate
- Nitrogen is necessary for growth as is carbon so if basic products are produced it indicates the use of citrate as well.
What is a polysaccharide?
5-13 Starch Hydrolysis
A polysaccharide is a type of macromolecule made up of many sugar units.
Why will starch not pass through the bacterial cell (plasma) membrane?
5-13 Starch Hydrolysis
Starch is too large to pass through the bacterial cell membrane.
Bacterial enzymes that can hydrolyze starch are __________ enzymes, namely __________ and __________.
5-13 Starch Hydrolysis
- Amylolytic enzymes
- Alpha-amylase
- Beta-amylase.
The overall reaction for the hydrolysis of starch involves breaking the polysaccharide down to __________.
5-13 Starch Hydrolysis
The overall reaction breaks starch down to glucose and maltose.
Why is it not possible to see either starch or its sugar subunits in starch agar?
5-13 Starch Hydrolysis
They are either too large or too soluble to be visible in the agar.
What is the purpose of adding gram’s iodine to starch agar plates after incubation?
5-13 Starch Hydrolysis
The purpose is to visualize starch hydrolysis by staining the agar.
Describe a positive result in this experiment.
5-13 Starch Hydrolysis
A positive result shows a clear zone around the colonies, indicating starch hydrolysis.
Describe a negative result in this experiment.
5-13 Starch Hydrolysis
A negative result shows no clear zone, indicating no starch hydrolysis.
After adding iodine, what would an uninoculated plate of starch agar look like? Why?
5-13 Starch Hydrolysis
It would appear blue-black due to the presence of iodine staining the starch.
Starch hydrolysis is one of the tests that aids in the differentiation of species in the genus Clostridium, members of which cause the diseases __________ and __________, and species in the genus Bacillus, which causes __________.
5-13 Starch Hydrolysis
- Botulism
- Tetanus
- Anthrax
What do the 2 bacterial genera mentioned have in common?
5-13 Starch Hydrolysis
Both genera are anaerobic and can form spores.
What conclusion can you draw from the fact that after iodine has been added, the clear area on starch agar around the colonies of the organism that is + for starch hydrolysis is only found a short distance from the colonies? If the organism is + for starch hydrolysis, why isnt the whole plate clear after iodine has been added?
5-13 Starch Hydrolysis
- The bacteria release amylase into their environment and have not been given enough time to grow out. Given enough time the plate could become clear when iodine is added.
ONPG is a synthetic artificial chemical that contains _____________ sugar on one half of its disaccharide-like structure. The disaccharide called ______________ most resembles ONPG.
5-5 ONPG
- Beta-Galactose
- Lactose
ONPG is digested by bacteria that produce the enzyme _____________________________.
5-5 ONPG
Beta-Galactosidase
ONPG is often used in place of the equivalent Phenol Red Lactose test because results can be read in as little as _________hours.
5-5 ONPG
Two
ONPG is the substrate in this test and it starts out the color ______________. Following digestion by the bacteria, the color ______________ will indicate a positive result when ________________ is produced.
5-5 ONPG
- White
- Yellow
- o-Nitrophenol
Explain how ONPG yields faster results than the Phenol Red Lactose test. (Hint: Lactose permease should be mentioned in your answer)
5-5 ONPG
- It faster because Phenol Red takes 24 hours to make lactose permease to get into the cell
Why is ONPG considered more accurate than the equivalent Phenol Red Lactose test?
5-5 ONPG
- It is permease independent because bacteria can mutate and no longer have functional lactose permease gene
The ONPG is a rapid test that only requires water, an ONPG tablet, and a heavy inoculum of bacteria. Why is it okay to handle the ONPG tablet with your hands (questionable aseptic technique) before placing the tablet in the
test tube?
5-5 ONPG
- Due to the test being rapid, the possible bacteria on your hand will be negligible and outnumbered compared to millions from inoculum
What is the purpose of the Acid-Fast Test?
3-8 Acid-Fast Stain
To stain cell walls and differentiate between acid-fast and non acid-fast cells
Escherichia coli
Organisms to know
Gram Negative
Rods
Staphylococcus epidermidis
Organisms to know
Gram Positive
Cocci
Bacillus anthracis
Organisms to know
Gram Positive
Endospore
Causes Anthrax
Klebsiella pneumoniae
Organisms to know
Capsule
Causes Pneumonia
Treponema pallidum
Organisms to know
Spirochete (negative stain)
Causes Syphilis
Mycobacterium tuberculosis
Organisms to know
Acid-fast
Bacillus shape
Causes tuberculosis
