Microlab Final Prep
What total magnification was used to view the yeast slide in class?
1000
Slides of bacteria are best viewed under the ____ objective.
100x
Blank 1 is a 1:100 dilution of the sample while Blank 2 is a 1:100 dilution of Blank 1. What total dilution of the sample is represented by Blank 2?
1:10^4
In a plate count, only plates containing between and colonies are used to do calculations.
30, 300
To make a 1:40 dilution, 1 ml of sample is added to what volume of diluent?
39 ml
List the following steps in the correct order in which they occur during the adjustment of the field iris diaphragm. (1) Move the condenser using the condenser height adjustment knob until there is a small circle of light with distinct edges in the microscope field. (2) Use the two condenser centering screws to move the illuminated area of the slide in the middle of the field of view. (3) Open the field iris diaphragm until the entire field of view is illuminated. (4) Close the field iris diaphragm by rotating the ring counterclockwise as far as it will go.
4,1,2,3
1 ml of a 1:100 dilution of a broth is placed in a plate, and nutrient agar is added. After incubation, 75 colonies are counted on the plate. What is the concentration of bacteria in the broth? (Express your answer in scientific notation with the correct units.)
7.5 x 10^3 cfu/ml
In order to be liquified, agar which has solidified must be heated to a temperature of ___ oC .
94
___ dyes, which are composed of negatively charged particles, are used in ___ stains.Acidic; negative
Acidic; negative
Who is credited with discovering penicillin
Alexander Fleming
When doing a plate count, which colonies are counted?
All of the colonies (inside and on top of the agar).
___ are substances produced by microbes that kill or inhibit other microbes.
Antibiotics
. _______________________ techniques are methods that are used to minimize contamination of media and other sterile materials.
Aseptic
Which one of the following is not a kingdom in the Domain Eukarya?
Bacteria
Why do the colonies within the agar look different than the colonies growing on top of the agar?
Because the agar cannot be broken down by the bacteria within the agar, this causes limited resource access and prevents growth.
Why is oil never used with the high power (40x) objective?
Because the lens is not sealed. The oil can seep into it and damage it.
What enzyme does the oxidase test test for?
Cytochrome C oxidase
The original culture was not mixed before transferring 1 ml to the first water blank.
Decrease, cells like to settle to the bottom, if the sample was drawn from the top, this would result in an unequal concentration and decrease the count. Increase, cells like to settle to the bottom, if the sample was drawn from the bottom, this would result in an unequal concentration and increase the count.
Blood agar is a...
Differential agar
DNA agar is a...
Differential agar
Most bacterial species can be identified on the basis of their cell morphology alone.
False; Most bacterial species look the same under the microscope
The enzyme catalase breaks down ____ resulting in the production of oxygen gas.
Hydrogen peroxide
Why is the coarse focus knob never used with the high power (40x) or oil immersion (100x) objectives?
It can run the stage into the lenses, damaging them.
Which of the following is not a characteristic of agar?
It is a source of nutrients
____ was the first antibiotic to come into use to treat bacterial infections.
Penicillin
Why is immersion oil not used with the high power (40X) objective?
The high power objective is not sealed and may be damaged if it comes in contact with the oil.
When you move the microscope slide on the stage from right to left, which way will the image appear to move?
The image appears to move left to right
Why is oil used with the oil immersion objective?
The oil decreases the scattering of light that occurs as the light rays travel from the glass of the slide into air and from air into the glass of the objective lens.
What effect does increasing the magnification have on the size of the area on the slide that is viewed?
The size of the area decreases magnification increases.
Why is a smear of bacteria heated after it has dried and before it is stained?
To keep bacteria from washing off during the staining process
What is the function of the oil when the oil immersion lens (100x) is used?
To prevent refraction of light, so the rays focus into the lens rather than scattering out, allowing you to see the image.
Computers, tablets, cell phones, and other electronic devices should not be used in the lab.
True
What does it mean when a microscope is referred to as "parfocal"?
When the microscope is in focus at lower magnifications, it will stay in focus as magnification increases
What does the Indole test test for?
a bacterium's ability to digest tryptophan into indole
___ are microorganisms in the Kingdom Protista that have chloroplasts and carry on photosynthesis.
algae
Chemicals that kill or stop the growth of pathogens on living tissue are referred to as ___.
antiseptics
The position of the ___ is/are determined by the numerical aperture of the objective lens that is being used.
aperture iris diaphragm lever
When streaking on a plate, how often will you flame the loop?
between each streak
After switching from the 40X objective to the 100X objective, adjustments should be made to which of the following?
brightness control knob fine focus knob field iris diaphragm aperture iris diaphragm
An antimicrobial drug that is effective against many different bacterial species is referred to as being ____.
broad spectrum
A(n) ____________________ will form on the surface of a plate of nutrient agar as an isolated bacterial cell repeatedly divides.
colony
Capsules will be ___ following the capsule stain.
colorless
Why are petri plates incubated upside down?
condensation
Members of the Kingdom Protista and Kingdom Fungi are considered to be eukaryotic because their cells:
contain nuclei
In doing these streak plate techniques, why is it important to put the lid on the plates between streaks while the inoculating loop is being flamed?
contamination
In the Gram stain, ___ is the primary stain.
crystal violet
During periods of environmental stress, some protozoa form dormant vegetative structures known as ____.
cysts
When it is added, the liquid nutrient agar splashes up on the inside of the lid during mixing.
decrease, the agar on the lid dries out, preventing the cells in the dried agar from growing colonies.
After being added, the liquid nutrient agar was not mixed sufficiently with the volume of water that was already in the plate.
decrease, the cells would not be distributed throughout the plate, resulting in multiple cells growing together into one colony, rather than individual colonies.
When it is added, the liquid nutrient agar was too hot.
decrease, the heat would kill all of the bacterial cells and result in no growth.
The Gram stain is an example of a ___ stain.
differential
Most people will have a difference in the vision of their right eye and their left eye. Which of the following parts of the microscope can be adjusted to compensate for this difference?
diopter adjustment ring
Counting the number of cells while looking through a microscope.
direct microscopic count
Chemicals that kill or stop the growth of pathogens on inanimate objects are referred to as ___.
disinfectants
The purpose of a streak plate is to..
distribute and separate individual cells within a mixed culture to allow for separate colony growth.
Which of the following microorganisms is the most difficult to kill?
endospore-forming bacteria
Which one of the following is a distinguishing characteristic of the microorganisms in the Domain Archaea?
extremophilic
After you are finished working with them, petri plates may be discarded in the garbage cans in the lab.
false
Backpacks or book bags can be kept at the lab benches as long as they are not on top of the lab bench.
false
If the results of my test don't fit what I think the bacterium is, the test must be wrong because I know I'm right.
false
Most fungi are heterotrophic decomposers, but a few are photosynthetic.
false
Your work area on the lab bench only needs to be disinfected at the beginning each laboratory period.
false
In lab, drinking from water bottles is allowed as long as the bottle is clearly labeled and is filled with water from outside the lab.
fase
Counting the number of colonies on a membrane that has trapped bacteria from a known volume of fluid.
filteration
Endospores will be ____ in color following the endospore stain.
green
Blood agar tests for..
hemolysis
When locating the specimen on a slide and initially focusing the microscope, which of the following objective lens or lenses should not be used?
high power or oil immersion
In the fungi, a ___ is an individual strand or filament that consists of many cells
hypha
Pipettes were not changed between dilutions
increase, the high concentration from the original sample would be carried through the dilutions.
What is a measure that can be taken to prevent a disease?
intervening in the transmission from the reservoir to new hosts protecting susceptible hosts eliminating the pathogen from the reservoir
Agar originates from ____.
marine algae
The ___ is used to move the slide on the stage as the slide is scanned.
mechanical stage control
Measurement of consumption of nutrients or measurement of production of a waste.
metabolic activity
In the Gram stain, iodine acts as the _____
mordant
noculation of tubes of lactose broth and estimating cell numbers by looking at the number of tubes positive for lactose fermentation
most probable number
The third requirement for an infectious disease to be spread is that the pathogen must enter a human host who is ____________ through the proper portal of entry
not immune
On the microscope, the objective lens with the highest magnification is the ___ lens.
oil immersion
Beef extract and peptone are added to culture media to ____.
provide nutrients
The protozoa in the phylum Rhizopoda (such as the amoeba) move by means of:
pseudopodia
A _____________________ culture consists of bacterial cells that all belong to the same species.
pure
After the completion of the Gram stain, Gram-positive bacterial cells are ____ in color.
purple
After the completion of the Gram stain, Gram-negative bacterial cells are ____ in color.
red
Which of the following is not a characteristic of the protozoa?
reproduce only by spore production
A filter paper disk containing an antimicrobial drug is placed on a plate that has been streaked with Escherichia coli. After incubation, it is observed that E. coli was not inhibited but grew right up to edge of the disk. Based on these results, E.coli is said to be ____ to the effects of the drug.
resistant
The coarse focus knob may be used with which of the following objectives?
scanner or low power
MacConkey agar is a...
selective and differential agar
what is considered a reservoir
soil water animals insects food
what factor could affect the size of the zone of inhibition
stability of drug the incubation time and temp growth rate of bacteria
Hemolysis means
the lysis and digestion of red blood cells
What is the index case?
the original infected person
A colony arises from just 1 bacterial cell.
true
Agar is sterilized by heating, but does not melt in the incubator.
true
All injuries, including minor ones, need to be reported to Sister Byington.
true
Petri plates should be labeled on the bottom half and not on the lid.
true
Students should wash their hands both at the beginning and at the end of the lab period.
true
Test tubes should not be picked up by their caps alone
true
The gas burners should be turned off when they are not being used.
true
Measurement of light transmission through a broth culture of bacteria.
turbidity
___ are fungi that are unicellular.
yeast
The halo of no growth of bacteria around a filter disk soaked with a chemical or drug is referred to as _________.
zone of inhibition