Microbiology Lab Exam #1
Quiz to study for McNeely's Lab Exam #1:Includes: oil immersionaseptic techniquestreaking for isolationgram stainingacid-fast stainingspecial staining
Questions and Answers
- 1.
The process by which a bacteriophage integrates its genetic material into the host bacterium's genome is called __________.
Explanation
Lysogeny is a fascinating example of viral reproduction where the bacteriophage, a virus that infects bacteria, doesn't immediately kill its host. Instead, it inserts its DNA into the bacterium's chromosome, becoming a prophage. This prophage replicates along with the bacterial DNA, remaining dormant for generations. Certain environmental triggers can cause the prophage to activate, leading to the production of new phages and the lysis (destruction) of the bacterial cell. This complex relationship between virus and bacteria highlights the intricate interactions in the microbial world.Rate this question:
- 2.
What are the three optical parts of a microscope?
Explanation
The three optical parts of a microscope are the eyepiece, abbe condenser, and objective lens. The eyepiece is the part that you look through to view the specimen, while the abbe condenser is responsible for focusing and directing light onto the specimen. The objective lens is the part that is closest to the specimen and magnifies the image. Together, these three parts work in conjunction to provide a clear and magnified view of the specimen under the microscope.Rate this question:
- 3.
Red colored objective is called what?
- A.
Scanning
- B.
Low-dry
- C.
Oil immersion
Correct Answer
A. ScanningExplanation
The red colored objective is called scanning.Rate this question:
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- 4.
What total magnification does the scanning objective have?
- A.
4
- B.
40
- C.
10
Correct Answer
B. 40Explanation
The total magnification of a microscope is calculated by multiplying the magnification of the objective lens with the magnification of the eyepiece. In this case, the question specifically asks for the magnification of the scanning objective. Since the answer provided is 40, it can be inferred that the scanning objective has a magnification of 40.Rate this question:
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- 5.
What is the real name for the blue-rimmed objective?
- A.
High-dry
- B.
Low-dry
- C.
Scanning
Correct Answer
A. High-dryExplanation
The correct answer is "high-dry" because it refers to a type of objective lens used in microscopy. High-dry objectives have a blue rim around them, which helps to distinguish them from other types of objectives. They are designed for use with a coverslip and a thin layer of immersion oil, allowing for higher magnification and resolution compared to low-dry objectives. Scanning objectives, on the other hand, are used for low magnification and are not characterized by a blue rim.Rate this question:
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- 6.
What is the real name for the yellow-rimmed objective?
- A.
Low-dry
- B.
High-dry
- C.
Oil immersion
Correct Answer
A. Low-dryExplanation
The correct answer is low-dry because it refers to a type of objective lens commonly used in microscopy. Low-dry objectives have a lower magnification power compared to high-dry or oil immersion objectives. They are designed for viewing specimens that do not require high levels of magnification and are often used for initial scanning or locating specific areas of interest on a slide. The term "low-dry" comes from the fact that these objectives are typically used with a lower amount of immersion oil or no oil at all.Rate this question:
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- 7.
What is the real name of the white-rimmed objective?
- A.
Scanning
- B.
Low-dry
- C.
Oil immersion
Correct Answer
C. Oil immersionExplanation
The correct answer is oil immersion. Oil immersion is the real name of the white-rimmed objective. This type of objective lens is used in microscopy to achieve higher magnification and resolution by immersing the lens in a special oil with a refractive index similar to that of glass. This allows for better light transmission and minimizes the loss of light due to refraction.Rate this question:
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- 8.
What is the total magnification for low-dry?
- A.
40
- B.
1000
- C.
100
Correct Answer
C. 100Explanation
The total magnification for low-dry is 100.Rate this question:
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- 9.
What is the total magnification for high-dry?
- A.
400
- B.
40
- C.
1000
Correct Answer
A. 400Explanation
The total magnification for high-dry is 400. This means that the image seen through the high-dry objective lens appears 400 times larger than the actual size of the specimen.Rate this question:
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- 10.
What is the total magnification for oil immersion?
- A.
10
- B.
400
- C.
1000
Correct Answer
C. 1000Explanation
Oil immersion is a technique used in microscopy to increase the resolving power and clarity of the image. It involves placing a drop of oil between the specimen and the objective lens. The oil has a refractive index similar to that of glass, which reduces the loss of light due to refraction. The total magnification for oil immersion is typically higher than other types of microscopy, such as dry lenses, because the oil allows for higher numerical aperture. Therefore, the correct answer of 1000 indicates that the total magnification for oil immersion is 1000x.Rate this question:
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- 11.
What are the functions of the abbe condenser?
- A.
Shuts off the light
- B.
Collects light
- C.
Condenses light
- D.
Alternate light source
- E.
Only light source
Correct Answer(s)
B. Collects light
C. Condenses light
D. Alternate light sourceExplanation
The Abbe condenser is a device used in microscopy to enhance the illumination of the specimen. It collects light from the light source and focuses it onto the specimen, increasing the intensity and uniformity of the light. By condensing the light, it improves the resolution and contrast of the image. Additionally, the Abbe condenser can also serve as an alternate light source when the primary light source is not available or not suitable for the specific observation.Rate this question:
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- 12.
What is the function of the iris diaphragm?
- A.
Turns light on, controls light
- B.
Adjustment for light coming through the abbe condenser; want it to ideally be in the middle; when looking through lens, light shouldn't be blinding.
Correct Answer
B. Adjustment for light coming through the abbe condenser; want it to ideally be in the middle; when looking through lens, light shouldn't be blinding.Explanation
The function of the iris diaphragm is to adjust the amount of light coming through the abbe condenser. Ideally, it should be set in the middle so that when looking through the lens, the light is not blinding. It helps control the amount of light that reaches the specimen, allowing for better visibility and clarity during microscopy.Rate this question:
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- 13.
Four microscopic morphologies of bacteria?
Correct Answer
cocci, coccobacilli, bacilli, spiralsExplanation
The question is asking for the four microscopic morphologies of bacteria. The correct answer includes four different shapes: cocci, coccobacilli, bacilli, and spirals. Cocci are spherical-shaped bacteria, coccobacilli are oval-shaped bacteria, bacilli are rod-shaped bacteria, and spirals are spiral-shaped bacteria. These different morphologies are important for classifying and identifying different types of bacteria.Rate this question:
- 14.
Parfocal lenses allow for us to be able to go between objectives with little adjustment of ___.
- A.
Iris diaphragm
- B.
Abbe condenser
- C.
Fine focus
Correct Answer
C. Fine focusExplanation
Parfocal lenses are designed to maintain focus when switching between objectives, meaning that little adjustment of the fine focus knob is necessary. This allows for smooth and efficient transitions between different magnifications without losing focus on the specimen. The iris diaphragm and Abbe condenser are not directly related to the ability to maintain focus when switching objectives.Rate this question:
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- 15.
What is the purpose of oil immersion?
- A.
To use oil to replace air and to prevent refraction at a glass-air interface.
- B.
To use oil to replace air to prevent absorption of bacteria
Correct Answer
A. To use oil to replace air and to prevent refraction at a glass-air interface.Explanation
The purpose of oil immersion is to use oil to replace air and prevent refraction at a glass-air interface. When examining specimens under a microscope, using oil immersion helps to increase the resolution and clarity of the image. By replacing the air between the glass slide and the objective lens with oil, the light rays can pass through without any refraction or distortion, resulting in a sharper image. This technique is commonly used in high-power microscopy, especially in fields like microbiology and pathology.Rate this question:
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- 16.
How do you get total magnification (equation)
Correct Answer
objective magnification x ocular magnificationExplanation
The total magnification is calculated by multiplying the magnification of the objective lens with the magnification of the ocular lens. This equation is used to determine the overall magnification of a microscope. The objective lens is responsible for magnifying the image of the specimen, while the ocular lens further magnifies the image for the observer. By multiplying these two magnifications together, the total magnification of the microscope can be determined.Rate this question:
- 17.
What is the appropriate order of clean up?1. clean stage with used alcohol swab2. clean ocular lenses with alcohol swab and take lense paper to clean/wipe of oculars, polish3. clean yellow, blue, white objectives
- A.
3, 2, 1
- B.
1, 2, 3,
- C.
2, 3, 1
Correct Answer
C. 2, 3, 1Explanation
First, the ocular lenses should be cleaned with an alcohol swab and then wiped with a lens paper to polish them (step 2). Next, the yellow, blue, and white objectives should be cleaned (step 3). Finally, the stage should be cleaned using a used alcohol swab (step 1). This order ensures that the lenses are properly cleaned and polished before moving on to clean the objectives and stage.Rate this question:
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- 18.
Why is sheep's blood used as media?
- A.
Non-fastidious bacteria
- B.
Fastidious bacteria
- C.
Requires extra nutirents
Correct Answer(s)
B. Fastidious bacteria
C. Requires extra nutirentsExplanation
Sheep's blood is used as a media for fastidious bacteria because it provides the necessary nutrients that these bacteria require for growth. Fastidious bacteria are unable to synthesize certain essential nutrients on their own and therefore rely on external sources. Sheep's blood contains a variety of nutrients, such as vitamins, minerals, and amino acids, that can support the growth and metabolism of these bacteria. By using sheep's blood as a media, it ensures that the fastidious bacteria have access to the extra nutrients they need to survive and thrive.Rate this question:
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- 19.
What are five characteristics of bacterial colonial morphologies?
- A.
Differences in size
- B.
Shape
- C.
Color or pigment
- D.
Weight
- E.
Toxicity
- F.
Texture
- G.
Density
Correct Answer(s)
A. Differences in size
B. Shape
C. Color or pigment
F. Texture
G. DensityExplanation
The five characteristics of bacterial colonial morphologies are differences in size, shape, color or pigment, texture, and density. These characteristics describe the physical appearance of bacterial colonies and can vary greatly depending on the species and conditions in which they grow. Size refers to the overall dimensions of the colony, shape describes the form or outline of the colony, color or pigment refers to the pigmentation or lack thereof in the colony, texture describes the surface or consistency of the colony, and density refers to the compactness or thickness of the colony. These characteristics are important for identifying and classifying different bacterial species.Rate this question:
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- 20.
Why should a petri dish not be left open for an extended period of time?
Correct Answer(s)
air contaminationExplanation
Leaving a petri dish open for an extended period of time can lead to air contamination. This is because the open dish allows airborne particles, such as dust, bacteria, or fungi, to settle on the agar surface. These contaminants can interfere with the growth of the desired microorganisms and introduce unwanted organisms into the culture. To maintain a controlled environment and prevent contamination, petri dishes should be covered and sealed properly after inoculation.Rate this question:
- 21.
What does streaking for isolation mean?
Correct Answer(s)
to break up colonies from two speciesExplanation
Streaking for isolation refers to a technique used in microbiology to separate and obtain pure colonies of bacteria or other microorganisms. It involves streaking a sample onto a solid growth medium in a pattern that gradually dilutes the cells, leading to the formation of isolated colonies. In the context of the given answer, streaking for isolation is used to break up colonies from two different species, allowing for the separation and identification of individual species present in a mixed sample.Rate this question:
- 22.
Purpose of inverting plates during incubation?
- A.
To not allow bacteria to unnecessarily clump or to let it dissolve into agar
- B.
To prevent buildup of condensation that would ruin the culture
Correct Answer
B. To prevent buildup of condensation that would ruin the cultureExplanation
Inverting plates during incubation helps to prevent the buildup of condensation that could potentially ruin the culture. By placing the agar side on top, any condensation that forms will fall away from the bacterial colonies, reducing the risk of contamination or interference with the growth of the culture. This method also helps to ensure that the agar remains intact and that the bacteria do not dissolve into the agar or clump together unnecessarily.Rate this question:
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- 23.
What is normal flora?
- A.
Air contamination
- B.
Buildup of condensation
- C.
Grows on different mucosal surfaces of the body
Correct Answer
C. Grows on different mucosal surfaces of the bodyExplanation
Normal flora refers to the microorganisms that naturally reside on various mucosal surfaces of the body, such as the skin, respiratory tract, gastrointestinal tract, and urogenital tract. These microorganisms, including bacteria, fungi, and viruses, coexist with the human body in a symbiotic relationship. They provide benefits such as aiding in digestion, producing vitamins, and preventing the colonization of harmful pathogens. Therefore, the correct answer is that normal flora grows on different mucosal surfaces of the body.Rate this question:
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- 24.
Four places normal flora exists
- A.
GI tract
- B.
Vagina
- C.
Armpit
- D.
Throat, mouth
- E.
Nose
- F.
Sinuses
Correct Answer(s)
A. GI tract
B. Vagina
D. Throat, mouth
F. SinusesExplanation
The correct answer includes four places where normal flora exists: the GI tract, vagina, throat, mouth, and sinuses. Normal flora refers to the microorganisms that naturally inhabit these areas of the body without causing harm. The GI tract is home to a diverse range of bacteria that aid in digestion. The vagina has a unique microbial community that helps maintain a healthy pH balance. The throat, mouth, and sinuses also have their own populations of bacteria that play a role in oral and respiratory health.Rate this question:
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- 25.
What color is serratia at room temperature?
Correct Answer(s)
redExplanation
Serratia is a type of bacteria that is commonly red in color at room temperature. This color is due to the production of a red pigment called prodigiosin, which gives the bacteria its distinctive red appearance. Therefore, the correct answer is red.Rate this question:
- 26.
What two things should you always do to enhance isolation of bacteria?
- A.
Flame and cool needle after primary inoculum
- B.
Firm touch, don't scoop
- C.
Scoop up bacteria
Correct Answer(s)
A. Flame and cool needle after primary inoculum
B. Firm touch, don't scoopExplanation
To enhance isolation of bacteria, two important steps should be followed. Firstly, after the primary inoculum, it is necessary to flame and cool the needle. This helps to sterilize the needle and prevent any contamination. Secondly, it is important to have a firm touch while handling the bacteria and avoid scooping. This ensures that the bacteria are properly isolated and prevents cross-contamination.Rate this question:
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- 27.
What is media?
- A.
Where bacteria is taken from originally
- B.
Broth or agar based
- C.
"base" for bacteria to be added to
Correct Answer(s)
B. Broth or agar based
C. "base" for bacteria to be added toExplanation
The correct answer is broth or agar based. Media refers to the substance used to cultivate and grow bacteria in a laboratory setting. It provides the necessary nutrients and environment for bacterial growth. In this case, the "base" refers to the medium on which bacteria are added. It can either be a broth or agar-based medium, both of which are commonly used in microbiology for bacterial culture.Rate this question:
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- 28.
What and where is agar from?
- A.
Solid form of media
- B.
Liquid form of media
- C.
Comes from seaweed
- D.
Comes from pebbles
Correct Answer(s)
A. Solid form of media
C. Comes from seaweedExplanation
Agar is a substance that is commonly used in laboratories as a solid form of media. It provides a solid surface for the growth of microorganisms. Agar is derived from seaweed, specifically red algae. It is extracted from the cell walls of these algae and then processed into a gel-like substance. Agar is preferred over other types of media because it is inert, meaning it does not react with the microorganisms being cultured. It also has a high melting point, allowing it to remain solid at higher temperatures, making it suitable for a wide range of experiments.Rate this question:
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- 29.
What are ways to tell if media is sterile?
- A.
Run controls
- B.
Inoculate with bacteria
- C.
No floaters in agar
- D.
No growth in broth
Correct Answer(s)
A. Run controls
C. No floaters in agar
D. No growth in brothExplanation
The ways to determine if media is sterile are by running controls, observing no floaters in agar, and observing no growth in broth. Running controls involves using a sample of the media without any bacteria to ensure that the media itself is not contaminated. If there are no floaters in the agar, it indicates that there are no visible contaminants present. Similarly, if there is no growth in the broth, it suggests that there are no viable microorganisms present in the media. These methods help to confirm the sterility of the media.Rate this question:
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- 30.
Why are culture tubes held at an angle?
Correct Answer(s)
to prevent air contaminationExplanation
Culture tubes are held at an angle to prevent air contamination because when the tube is tilted, the risk of airborne particles entering the tube is reduced. By keeping the opening of the tube facing downwards, gravity helps to prevent any contaminants from falling into the culture. This is particularly important in microbiology, where maintaining a sterile environment is crucial for the growth and study of microorganisms. Holding the culture tube at an angle is a simple yet effective measure to minimize the risk of air contamination and maintain the integrity of the culture.Rate this question:
- 31.
What are two possible errors which could have occurred if you find your subcultures had no growth after incubation for 48 hours?
- A.
Not a sterile plate
- B.
Forgetting to inoculate
- C.
Could have killed bacteria with heat from un-cooled needle
Correct Answer(s)
B. Forgetting to inoculate
C. Could have killed bacteria with heat from un-cooled needleExplanation
If there is no growth observed after 48 hours of incubation, it suggests that the subcultures were not properly inoculated with bacteria. Forgetting to inoculate means that no bacteria were added to the plate, resulting in no growth. Another possible error could be the use of an un-cooled needle to transfer the bacteria, which could have killed the bacteria due to the heat.Rate this question:
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- 32.
In microbiology, what is the purpose of using a Gram stain in laboratory analysis?
- A.
To determine the bacterial load in a sample
- B.
To differentiate bacterial species based on cell wall composition
- C.
To identify the presence of viruses in a sample
- D.
To assess the viability of bacteria in a sample
Correct Answer
B. To differentiate bacterial species based on cell wall compositionExplanation
The Gram stain is a crucial differential staining technique used in microbiology to classify bacteria into two major groups: Gram-positive and Gram-negative. This classification is based on the differences in cell wall compositions of the bacteria, which affect how they retain the crystal violet dye during the staining process. Gram-positive bacteria retain the dye and appear purple, whereas Gram-negative bacteria do not and appear pink after a counterstain. This technique helps in determining appropriate treatment strategies and understanding bacterial structure.Rate this question:
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- 33.
What does a positive acid-fast stain look like?
Correct Answer
fuscia/pink clusters of rods; blue cocciExplanation
A positive acid-fast stain appears as fuscia/pink clusters of rods and blue cocci. This staining technique is used to identify bacteria that have a waxy cell wall, such as Mycobacterium tuberculosis. The waxy cell wall prevents the stain from being washed out, resulting in the bacteria retaining the pink color. The blue cocci mentioned in the answer might be unrelated to the acid-fast stain, as cocci are typically round-shaped bacteria and not commonly stained using this technique.Rate this question:
- 34.
What group of organisms are considered acid-fast?
Correct Answer
mycobacteriumExplanation
Mycobacterium is a group of organisms that are considered acid-fast. Acid-fast organisms have a unique cell wall structure that allows them to retain a stain even when exposed to acid. This property is mainly due to the presence of a waxy substance called mycolic acid in their cell walls. Mycobacterium includes important pathogens such as Mycobacterium tuberculosis, which causes tuberculosis, and Mycobacterium leprae, which causes leprosy. These organisms are difficult to stain and are resistant to many disinfectants, making them challenging to treat and control.Rate this question:
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