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Micro Lab Final
Terms in this set (156)
both numerical aperture and wavelength of light.
The resolving power of a microscope is a function of
the stage and the objective lens.
The coarse and fine focus knobs adjust the distance between
A microscope that maintains the focus of a specimen even when the magnification is increased is called _______.
The total magnification achieved when using a 100X oil immersion lens with 10X binocular eyepieces is ________.
closing down the diaphragm
The most useful adjustment for increasing image contrast under low-power magnification is
center the object of interest and add a drop of oil to slide.
Before the oil immersion lens is rotated into place, you should
Use both hands with one on the base and one around the arm
Which of the following correctly describes the position of your hands while carrying a microscope to and from the laboratory bench?
The larger field of view enables you to easily locate the specimen.
Starting with the low-power lens when viewing a slide offers what advantage?
The ______ the working distance of an objective lens, the ______ the magnification.
A microscope that allows light to pass directly through the condenser to the eye is called a _______ microscope.
Which of the following lenses does NOT affect the magnification of the specimen?
unstained living cells.
Darkfield microscopes are preferred over brightfield microscopes when observing
What type of microscope is particularly useful for diagnosing syphilis by observing living spirochaetes in a patient specimen?
When using a ______ microscope, the background of the field is dark and the specimen is brightly illuminated.
If a darkfield condenser causes all light rays to bypass the objective, where does the light come from that makes an object visible in the dark field?
diaphragm with an annular stop and a phase plate.
A phase-contrast microscope differs from a brightfield microscope by having a
Motility of cells
Which of the following would be best observed in a bacterial cell by using phase-contrast microscopy?
living organisms on a slide with a cover glass.
The phase-contrast microscope is best suited for observing
When direct and diffracted light rays are brought into exact phase with each other, the result is _______, increasing the amplitude of these waves and the brightness of the object.
When two light waves of equal amplitude are in reverse phase, a dark object is produced and this is called ________.
The heat filter in a fluorescent microscope is used to eliminate nonuseful, heat-generating
Specific proteins on or in a cell can be tagged with fluorochromes that have been chemically linked to
screen out exciting light rays.
The barrier filter in the fluorescence microscope is kept in position to
Fluorescence eventually diminishes with continued exposure to UV light due to _______.
If 10 divisions of the ocular micrometer line up with two divisions of the stage micrometer, what is the correct mathematical calculation used in calibration?
The size of the field changes with increased magnification.
Why must the entire calibration procedure be performed for each objective lens of a microscope?
If the calibrated value for the ocular micrometer at this magnification is 2 microns, what is the total length of the yeast cell and bud on the right?
The discovery of rRNA and its use in analyzing genetic relatedness
Please choose the development that led to the new three-domain system of classification.
Please choose the answer that best fills in the blanks of this sentence in the correct order. Algae and protozoa are in Domain ______ and cyanobacteria are in Domain _____.
The genus _______ is an extremely important member of the apicomplexan group because several of its species are the causative agents of malaria.
_______ are marine algae that are responsible for "red tides" when great numbers of cells form blooms in the water.
What were previously known as "blue-green algae?"
Which of the following does not describe cyanobacteria?
You are looking at a drop of pond water and in the field of view, you observe a moving unicellular organism with short hairlike structures surrounding the outside surface of the cell. You are most likely observing an example of a/an ________.
Bacteria are _______, meaning that they are distributed everywhere.
The level of microbial contamination on an agar plate is measured as the ______ of colonies.
50 to 100 colonies
You exposed this TSA plate to the air of the laboratory for 30 minutes, and then you incubated the plate for 24 hours at 37 degrees Celsius. What would be the correct quantitative evaluation of the degree of contamination on this plate?
A mass of intermeshed hyphae is a _______.
Please choose the answer that best completes the blanks of this sentence in the correct order. ________ are fungi that contain microscopic intertwining filaments called hyphae, whereas _______ are fungi that lack hyphae.
_______ fungi are those species that occur as either molds or yeast, depending on environmental conditions such as temperature and nutrient availability.
What medium is commonly used when culturing molds on agar plates?
Which of the following is not a type of asexual fungal spore?
Which of the following is not a type of sexual fungal spore?
_______ are nonmotile asexual fungal spores that form on specialized hyphae and may include phialospores, blastospores, chlamydospores, or arthrospores.
Asexual spores that form within a thin-walled sac are referred to as ________.
Passing the slide through the flame of a burner several times after the smear has completely dried.
What is heat fixation?
Before heat fixation, a wet smear of bacterial cells on a slide must first be
Water is applied to the slide before emulsifying cells from a solid medium.
How does smear preparation of cells from a liquid medium differ from preparation of cells from a solid medium?
Please choose the answer that best completes the blanks of this sentence in correct order. Basic or cationic dyes have a ______ charge which are attracted to negatively-charged bacteria, whereas acidic or anionic dyes have a ______ charge and do not stain bacteria.
There may be cells of different shapes, sizes, and arrangements.
You make a smear of E. coli and then simple stain the slide with methylene blue. If you failed to use correct aseptic technique by not sterilizing the loop before picking up the bacterial sample for the smear, what results may be seen under the microscope?
A _______ stain is one that colors the background surrounding the cell, leaving the cell itself unstained.
either India ink or nigrosin
For the negative stain procedure, one can use
Heat fixation is not performed so cells do not shrink.
Why is negative staining useful for accurately determining cell size?
What type of microscopy produces an image of unstained cells that is similar to one achieved by negative staining?
crystal violet; copper sulfate
Please choose the answer that best completes this sentence in the correct order. In the Anthony method of capsular staining, the stain used is _________ and the decolorizer used is an aqueous solution of 20% ___________.
They are able to evade immune defenses.
Why are encapsulated strains of Streptococcus pneumoniae much more likely to cause disease than strains that do not produce a capsule?
The Gram stain is an example of a _______ staining procedure, which takes advantage of the fact that cells or parts of cells react differently and can be distinguished by the use of two different dyes.
Please choose the answer that best fills in the blanks of this sentence in the correct order. Gram-________ cells stain purple whereas gram-_______ cells stain pink or red when using the Gram stain technique.
Please choose the answer that best completes this sentence in the correct order. The figure on the left represents gram-______ cell envelope whereas the figure on the right represents a gram-______ cell envelope.
It is gram-negative.
You collected a sample from a patient with a suspected STI. After Gram staining, you observed this under the microscope. What can you conclude about this microbial agent?
Malachite green; safranin
Please choose the answer that best completes the blanks of this sentence in the correct order. _______ is used to stain the endospore, and _______ is the stain used to stain the vegetative cell in the Schaeffer-Fulton method of spore staining.
Older cultures are most likely to produce spores due to depleted nutrition.
Why does culture age affect the results of a spore stain?
Please choose the answer that best completes the blanks of this sentence in the correct order. After acid-fast staining, Mycobacterium tuberculosis would be _______ in color, whereas Proteus vulgaris would be ________ in color.
The presence of mycolic acid in their cell walls
What makes Mycobacterium particularly resistant to staining?
Motility can be observed by creating a __________, a slide preparation in which a drop of living organisms is placed onto a slide and covered with a cover glass for microscopic examination.
Long movements of objects in multiple directions in the same field
Which of the following describes a motile bacterium as observed in a wet mount?
What bacterial cellular structure(s) is/are detected through the use of wet mounts or SIM tubes?
It decreases the potential for infection of the handler.
Why is a SIM tube often preferred over a wet mount when working with pathogenic bacteria?
Which of the following CANNOT serve as a nitrogen source?
onsider a medium with the following ingredients:
Ammonium phosphate (NH4H2PO4)
Sodium chloride (NaCl)5.0g
Magnesium sulfate (MgSO4.7H2O)0.2 g
Potassium phosphate (K2HPO4)
Water (H2O) 1.0 liter
Which term correctly describes this type of medium?
Media which contain substances such as antibiotics, dyes, and other compounds to inhibit the growth of certain types of bacteria are called ________ media.
Please choose the description that best fits a medium that has been designed to indicate the growth of Staphylococcus aureus based on its ability to ferment mannitol.
Which of the following descriptive terms fit Medium 1?
Both selective and differential
Which of the following descriptive terms fit Medium 2?
You are interested in studying the gram-negative bacteria that may be found in ground meat. You would like to use a medium that will enable the growth of most species of gram-negative bacteria, while inhibiting gram-positive bacteria. This would be a __________________ medium.
Bring the medium to a boil while stirring.
What is the best way to dissolve agar in a medium as you are preparing it?
It is solid at room temperature, but liquid at temperatures that are tolerated by bacteria.
Why is agar a useful solidifying agent in microbiology?
Add several drops of HCl and recheck the pH.
Upon checking the pH of the medium you are preparing, you realize that the pH is 8.0 and ideally should be 7.0. Which of the following steps should be used to adjust the pH?
Which method is usually used to sterilize most agar media?
Bacterial cultures can be preserved by freeze-drying, also known as _________.
Suspend bacteria in a small vial of glycerol and place in a -196oC freezer.
Choose the most appropriate method to freeze a bacterial culture for preservation.
Endospores will promote and enable culture preservation.
Predict the effect of endospores on preservation of a bacterial culture.
Most Probable Number (MPN)
Which method is often used to test for the presence of coliforms in drinking water?
Standard Plate Count (SPC)
Which method used to determine numbers of bacteria in a sample involves the preparation of a series of dilutions of the sample in sterile water, adding measured volumes of each dilution to melted nutrient agar plates, making pour plates, incubating, counting colonies, and multiplying colony counts by dilution factors to determine the number of bacteria in the sample?
An indirect method of estimating bacterial numbers is based on the turbidity of the sample. A ________ can be used to determine the turbidity by measuring absorbance.
When performing a Standard Plate Count, plates that contain __________________ colonies are selected for counting with the Quebec Colony Counter.
A total of 145 colonies were counted on the plate that received 1.0 mL of the 1:10,000 dilution of a specimen. What is the bacterial count for the original specimen?
A total of 75 colonies were counted on the plate that received 1 mL of a diluted specimen. After calculating, it is determined that the total bacterial count in the original specimen was 75,000,000 colonies per mL. What was the dilution factor for the plated sample?
Which of the following increases as the number of bacteria in a sample increase?
It would increase and then level off.
You measure the absorbance of a bacterial culture two hours after inoculating a sterile medium, and then you continue to measure the absorbance every two hours for a total of 3 days. If you plotted the absorbance over time, what would the graph look like?
to enable staining and observation of fungal sporulating structures in situ.
The primary goal of fungal slide cultures is
Lactophenol cotton blue
Which of the following stains is used for staining slide cultures?
A bacterial species that cannot tolerate the presence of oxygen and will only grow in the absence of oxygen is classified as a(n)
Organisms such as Pseudomonas spp. and Bacillus spp. need oxygen as the final electron acceptor in the electron transport chain and must have adequate oxygen in their immediate atmosphere in order to grow. These organisms are classified as
Some organisms don't require oxygen for growth since they use fermentation to harvest energy, but are able to grow in the presence of oxygen even if they don't use it. These organisms are classified as
Some organisms exhibit flexibility in terms of their energy harvesting reactions. If provided with oxygen, they will obtain energy through aerobic respiration. If in an environment without oxygen, they will turn to fermentation to satisfy their energy needs. These organisms are classified as
Some organisms require oxygen in significantly reduced amounts, such as 5% oxygen. These organisms are classified as
Reazurin indicates the presence of oxygen in the media.
What is the role of reazurin in fluid thioglycollate medium, TGYA shake tubes, and Brewer's anaerobic agar?
An anaerobic environment has been successfully established within the jar.
You have placed cultures in a GasPak anaerobe jar, activated the chemical packet, and sealed the jar. Later in the day, you check the jar and notice that the methylene blue strip is colorless. What does this indicate?
Throughout the tube but more at the top
Where would you predict an facultative anaerobe would grow in a tube of fluid thioglycollate medium?
A little below the surface of the broth
Where would you predict a microaerophile would grow in a tube of fluid thioglycollate medium?
Listeria monocytogenes is a human pathogen, growing readily in the human body. It poses a problem in food storage because of its ability to grow in refrigerated foods, such as unpasteurized milk or deli meats. A mesophilic organism that is capable of growth at refrigerator temperatures is known as a ______.
Taq polymerase is a DNA polymerase enzyme that demonstrates maximal activity around 72° C. The organism from which this enzyme was isolated would most likely be classified as a
You are studying a bacterium found in the normal intestinal biota of humans and most other mammals, and you are doing an experiment to determine the optimum growth rate of this bacteria. You have inoculated five nutrient broths, and are incubating one broth at each of the following temperatures: 5° C, 25° C, 38° C, 42° C, and 55° C. At which temperature would you predict to see the optimum growth rate?
The steep decrease seen in the temperature range growth curve after the optimum is related to the _____________ of enzymes.
At the bottom of the tube
Where would you predict an obligate anaerobe would grow in a tube of fluid thioglycollate medium?
This organism is an obligate anaerobe and requires the absence of oxygen for growth.
You inoculate a plate of general-purpose medium with Clostridium sporogenes, and you incubate it for 48 hours at its optimum temperature. When you remove the plate from the incubator, you notice that there is no growth on the plate. Besides errors made in inoculation, what else could explain this lack of growth?
The working stock culture is used for all subcultures, staining, biochemical testing whereas the reserve stock culture is stored in the refrigerator and used only if the working stock culture becomes contaminated.
How is the reserve culture used differently from the working stock culture?
The slant should be refrigerated.
How should the reserve stock culture be stored over the several weeks that you are working on your "unknown?"
Older cultures of a gram-positive bacteria may stain as gram-negative.
Why are young cultures (24-48 hr) preferred for Gram staining?
KOH string test
Which of the following can confirm the results of the Gram stain?
Endospore stains need only be done on
The organism is nonmotile.
You have inoculated a tube of SIM (sulfide-indole-motility) medium and after incubation, the medium remained clear and you can only see growth right along the inoculation stab. What does this indicate?
do an endospore stain again on an older culture.
Multiple Choice: You are working with an organism which is a gram-positive bacillus. You did an endospore stain when it was 24 hours old, but failed to see any endospores. Before ruling out the possibility that this organism is an endospore former, you should
When examining your culture, the colonies appear to be quite uniform in appearance and the culture appears to be pure. Upon observation of a Gram stained slide, you see what looks like cocci and short bacilli. What is the most likely morphology of these microorganisms?
Which of the following is most critical to perform an acid-fast stain on?
Fluid thioglycollate medium
Which of the following can be used to determine the oxygen requirements of an organism?
It is stabbed with an inoculating needle.
How is the gelatin medium inoculated?
The terms, granular, flaky, flocculent, turbid, and pellicle, would be used to describe growth in or on
Any liquefaction of the gelatin medium by an organism indicates the presence of
Oxidative reactions used by aerobic bacteria to generate ATP use ______ as a terminal electron acceptor.
pyruvate or a derivative.
The final electron acceptor in fermentation reactions is usually
substrate level phosphorylation.
The ATP generated during fermentation reactions is generated by
Which biochemical test would be most appropriate for determining whether an organism uses oxidative or fermentative metabolism?
The organism demonstrates oxidative metabolism.
After incubation of a set of O/F glucose tubes, the tube without mineral oil turned yellow, while the tube with mineral oil remained green. What does this indicate?
red in the Voges-Proskauer test.
An organism that ferments glucose via the 2,3-butanediol pathway will be
Which of the following is detected by the methyl red (MR) test?
What is the substrate for the catalase enzyme?
The organism is fermenting glucose.
A phenol red glucose broth with a Durham tube has been inoculated and incubated. After 48 hours, the broth is turbid and bright yellow, and approximately half of the contents of the Durham tube have been displaced with gas. Interpret these results.
the test organism did not hydrolyze starch.
After 48 hours of incubation, the surface of a starch agar plate growing a test bacterium is flooded with iodine. The entire plate turns into a blue-black color. This indicates that
skim milk agar plate.
Casein hydrolysis is detected using a
Spirit blue agar is used to test for
An organism that hydrolyzes starch possesses the enzyme ________.
Which enzyme will hydrolyze casein?
The pH would decrease.
Predict how the pH of a medium might change if triglycerides are hydrolyzed.
the production of indole.
Tryptophan hydrolysis results in
methyl red test.
The "M" in the IMViC reaction set refers to
The substrate for H2S production in Kligler's iron agar is
Provided with the following test results, select the most likely genus designation of this gram-negative bacillus. Refer to the separation outlines in your lab manual for help in determining your answer.
The terms crateriform, umbonate, convex, flat, and raised are all used to describe the _______ of a colony.
Inoculation of MR-VP broth, followed by MR and VP tests
Which of the following can determine the particular fermentation pathway used by a fermenting microorganism?
an increase in pH causing a color change of a phenol red indicator to bright pink.
The presence of urease is detected by
What ingredient is found in both Kligler's iron agar and SIM that enables the detection of H2S?
Based on the separation outlines in your lab manual, which of the following is an organism with these characteristics?
**not acid fast
Using the separation outlines in your lab manual, a motile, gram-negative bacillus that is classified as a facultative anaerobe could be which of the following?
The goal of ______ technique is to minimize the contamination of both original and newly inoculated cultures as well as protect the laboratory handler from contamination.
All of the choices are correct.
A disinfectant is used on your work surface
removed and held with the fingers of the loop hand.
To retrieve a sample from a culture tube with an inoculating loop, the cap of the tube is
until the entire wire is bright red.
An inoculating loop or needle is sterilized in a flame
Please choose the answer that best completes the blanks of this sentence in the correct order. The name of the organism should be labeled on the _______ of an agar plate, and the plate should be incubated with the lid _____.
The plate lid is kept closed or lifted only slightly when inoculating.
How is air contamination prevented when an inoculating loop is used to introduce or remove organisms from an agar plate?
You have a nutrient broth, an agar slant, and an agar plate with bacterial growth in or on each. If you wanted to evaluate the macroscopic appearance of the bacteria growing in or on the medium, which of the cultures would be the best choice?
A ______ is a mound of cells on a solid medium that represents the progeny from one original bacterial cell.
Please choose the answer that best completes the blanks of this sentence in the correct order. The ______ plate method involves spreading an inoculum onto the surface of a plate in a pattern that results in isolated colonies in some areas of the plate after incubation, whereas the ______ plate method involves diluting an inoculum into several melted agar tubes and then adding their contents into plates for solidification and incubation.
reducing the number of inoculated organisms so that isolated colonies can develop.
When preparing pure cultures, dilution is necessary for
It requires less skill.
What advantage does the pour-plate method have over the streak-plate method?
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