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BISC300 Lab Practical/Final

Terms in this set (67)

In the Indole test, the activity of what enzyme is tests for?
Tryptophanase
If there is a positive indole test, what amino acid must have been present?
Tryptophan
What is tested for in the Methyl Red test?
Glucose fermentation and gas production
What enzyme is present in a positive Methyl Red test?
Formic Hydrogenlyase
If a pure culture has positive Methyl Red and butanediol production was also tested for, would you expect a positive or negative result? Explain.
You would expect the test for butanediolh (Voges-Proskauer) to be NEGATIVE because the glucose is fermented by the formic hydrogenlyase already
What is tested for in the Voges-Proskauer test?
Acetoin is tested for because it is a necessary precursor for butanediol formation
Name three media which are stabbed when they are inoculated
SBA plates, Simmons citrate slants, and TSIA slants
Why does the agar turn blue in a positive Citrate test?
Because the pH increases due to the bacteria consuming the citrate as their only source of carbon
Name two bacteria which give a positive result on the Citrate test
Enterobacter cloacae, Serratia marcescens, and Salmonella Enteritidis
If a Proteus culture is inoculated into a urea broth and a red-purple color is observed after a 20 minute incubation at 37 degrees Celsius, is this a positive or negative test?
Positive
What enzyme must be present for a positive urea reaction?
Urease
E. coli, S. Aurues, and Enterococcus faceless display what type of oxygen requirements?
Facultative aerobe (can grow without oxygen but grow better with it)
Name an anaerobic organism that was discussed in lab this semester
Clostridium sporogenes
Describe Brownian Motion
The normal vibration of cells cause by random activity of water molecules
The oil immersion objective provides what total magnification?
1000x magnification
Which part of the microscope has the purpose of focusing the radiation from the light source onto the specimen?
Condenser
What type of microscope is used in this lab?
Brightfield microscopes
What does parfocal mean?
Once you adjust the microscope you change between the objectives without having to refocus
Name a structure that is extremely heat resistant
Endospores
What is the solution used to clean the slides?
Alconox
How many times is a smear from a liquid culture heat fixed?
It is heat fixed once by passing the slide through the flame 3-4 times
How many minutes is a smear from a liquid culture allowed to air dry?
5 minutes
How many times is the loop flamed when a quadrant streak is performed?
5 times
Name the only eukaryote that was encountered in this lab
Saccharomyces cerevisiae
Name the bacterium that produces a red pigment
Serratia marcescens
What is the name of the red pigment?
Prodigiosin
What is the name of the test method used for antibiotic sensitivity?
Kirby-Bauer (uses disks impregnanted with antibiotics)
What is the test medium for the antibiotic sensitivity testing?
Mueller-Hinton agar
What is measured in the antibiotic sensitivity testing?
The zone of inhibition
What medium is used to test for hemolysis?
Sheep's blood agar
What is the equation for determined doubling time?
k= (logx_t-logx_0)/0.301t

and doubling time = 1/k
What test uses Kovac's reagent?
The Indole Test
Describe the negative test for the Indole Test
Clear or yellow layer at the top
A positive methyl red test demonstrates what?
The broth turning red
For the methyl red test, is orange + or -? yellow?
Both are negative
What test contains pH indicator bromthymol blue?
The Citrate Utilization test
What is the original color of the agar used in the Citrate test?
Green
Bacteria may be distinguished on the basis of surface differences. What are these differences called?
Serotypes
When focusing on a slide, you should start under what objective?
10x
Which of the following commonly produce endospores?
a)Klebsiella
b)Clostridium
c)Bacillus
d)Spirillum
e) both b and c
E.
Clostridium and Bacillus
What is the difference between resolution and focus?
Focus makes an image more sharp
Resolution is the smallest 2 objects can be and still be seen as separate
Difference between dye and stain?
Dye is what is used to obtain visibility of an organism (noun), stain is the process of dying (verb)
What is the purpose of heat fixing a slide?
To make cells uniform and stick to the plate
How many groups does a Gram stain separate bacteria into?
Two- Gram positive and Gram negative
True or False:
The Gram positive bacteria retain the purple color even after exposure to alcohol?
True
What is the purpose of using the pour plate method?
To create separate colonies
During a gram stain, the 95% ethanol is added to the slide to serve what purpose?
To dehydrate and decolorize, in the case of a gram negative bacteria
True or False:
Obligate anaerobe bacteria requires oxygen to grow?
False, they are poisoned by oxygen
True or False:
Bacteriolytic agents kill bacteria by cell lysis?
True
What is used as a mordant in the Gram staining process?
Iodine
What is the purpose of the pigment produced by the bacteria Serrate marcescens when incubated at room temperature?
To protect from UV light
True or False:
Bacteria population with a high cell concentration will have a high percent transmittance
False
The growth phase where an organism adjusts to a new environment and there is an increase in individual cell size is know as the ____ ______
Lag phase
Name two factors that drive the death phase of a bacterial growth cycle
Accumulation of toxins, not enough oxygen
Why does the third plate in the pour plate exercise show the best separation of colonies?
It is the most pure and diluted
State two advantages of using the wet mount technique in determining bacterium motility
1. No distortion
2. Easily visible, less technical
Why does the hanging drop method of determining bacterium motility allow longer observations of living organisms?
It uses a larger drop size of the culture which allows a larger percentage of the bacteria to survive
What are the bacteria that are present in the human body that do not cause harm referred to as?
Microbiota
What type of medium is used in the culture method of determining bacterium motility?
Semisolid medium
True or False:
All enteric bacteria ferment glucose
False
What is the purpose of the TSIA media?
To determine if a bacteria can ferment carbohydrates
What is alpha hemolysis?
Incomplete lysis of cells, pinkish around the colony with green due to potassium leakage from the blood cells
Name one bacteria that shows beta hemolysis on SBA
S. aureus
True or False:
Mannitol Salt agar (MSA) is selective for Streptococcus pyogenes
False (selective against it)
Staphylococcus Aureus grows well on MSA medium and turns the agar yellow because ...?
It ferments the mannitol, producing acid
What broth does the methyl red test of the IMViC series use?
MR-VP broth
Name 2 Gram positive rod shaped bacteria
Bacillus subtillis, Bacillus ceraceus
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