Question 1

A microbiologist must culture a patient's feces for intestinal pathogens.Which of the following would likely be present in selective media for analyzing this fecal specimen?

Accepted Answer

Bile salts are often added to selective media for analysis of fecal specimens as they inhibit the growth of certain bacteria while allowing the growth of others. NaCl, sheep red blood cells, thioglycolic acid, and peptone are not typically added to selective media for this purpose.

Question 2

A nutrient medium that has all of its chemical components identified and their precise concentrations known and reproducible would be termed

Accepted Answer

A nutrient medium that has all of its chemical components identified and their precise concentrations known and reproducible would be termed synthetic.

Question 3

Which of the following magnifies the specimen to produce the real image of the specimen?

Accepted Answer

The objective lens is responsible for magnifying the specimen to produce the real image of the specimen.

Question 4

A pure culture contains only

Accepted Answer

A pure culture contains only one species of microorganism, which means that it is not a mixture of different species of microbes. Choices B and C are not fully accurate since there are other microorganisms besides bacteria that can be in a pure culture, and a variety of microbes from one source would not be considered a pure culture.

Question 5

All of the following are examples of different types of microbiological media except

Accepted Answer

Petri dish is not a type of microbiological media; it is a container used to hold the media. Broth, enriched media, agar, and gelatin are all types of media used for growing microorganisms.

Question 6

A common medium used for growing fastidious bacteria is

Accepted Answer

Fastidious bacteria are those that require specific growth factors that are not present in standard culture media. Chocolate agar, also known as heated blood agar, is a type of agar that is made by adding sterile, defibrinated blood to a nutrient-rich base. The heating process causes the blood cells to release factors that support the growth of a wide range of fastidious bacteria, making it an ideal medium for their cultivation.

Question 7

A microbiologist inoculates Staphylococcus aureus into a culture medium.Following incubation, both Staphylococcus aureus and Staphylococcus epidermidis are determined to be growing in this culture.What is the most likely explanation?

Accepted Answer

The presence of two different species, Staphylococcus aureus and Staphylococcus epidermidis, in the same culture suggests that the culture is contaminated with more than one type of bacteria.

Question 8

Which of the following is essential for development of discrete, isolated colonies?

Accepted Answer

Solid medium is essential for development of discrete, isolated colonies as it provides a surface for microbial growth that allows for individual colonies to form without being disturbed or in contact with each other. Broth medium, differential medium, selective medium, and assay medium do not provide this type of surface and may lead to overlapping or mixed colonies.

Question 9

A reducing medium contains

Accepted Answer

A reducing medium contains substances that remove oxygen, which creates an anaerobic environment suitable for the growth of anaerobic bacteria.

Question 10

The term that refers to the purposeful addition of microorganisms into a laboratory nutrient medium is

Accepted Answer

Inoculation is the term used to describe the purposeful addition of microorganisms into a laboratory nutrient medium. It is a common technique used in microbiology to grow and study different types of bacteria, viruses, and fungi.

Question 11

Which method often results in colonies developing down throughout the agar and some colonies on the surface?

Accepted Answer

The pour plate method involves adding melted agar to a small amount of inoculum before pouring the mixture into a Petri dish. This allows the bacteria to grow throughout the depth of the agar, resulting in colonies both on the surface and down throughout the agar. The streak plate and spread plate methods typically only result in colonies on the surface of the agar.

Question 12

A microbiologist inoculates Staphylococcus epidermidis and Escherichia coli into a culture medium.Following incubation, only the E.coli grows in the culture.What is the most likely explanation?

Accepted Answer

The culture medium must be selective, which means it allows the growth of certain types of organisms while inhibiting the growth of others. In this case, the medium was selective for E. coli and inhibited the growth of Staphylococcus epidermidis.

Question 13

The Six "I's" of studying microorganisms include all of the following except

Accepted Answer

The six "I's" of studying microorganisms are inoculation, incubation, isolation, inspection, information gathering, and identification. Infection is not one of the "I's" involved in studying microorganisms.

Question 14

Mannitol salt agar is selective for which bacterial genus?

Accepted Answer

Mannitol salt agar contains high levels of salt that only Staphylococcus species can grow on, making it selective for this bacterial genus.

Question 15

If a microbiologist is studying a specimen at a total magnification of 950X, what is the magnifying power of the objective lens if the ocular lens is 10X?

Accepted Answer

The total magnification is the product of the magnifying powers of the ocular lens and the objective lens. Given a total magnification of 950X and an ocular lens of 10X, the objective lens magnification is 950X / 10X = 95X.

Question 16

A microbiologist decides to use a nutrient medium that contains thioglycolic acid.What type of microbe is she attempting to culture?

Accepted Answer

Thioglycolic acid is a reducing agent that helps create an anaerobic environment, so the microbiologist is attempting to culture anaerobic microbes.

Question 17

Which of the following characteristics refers to the microscope's ability to show two separate entities as separate and distinct?

Accepted Answer

Resolving power, also known as resolution, refers to the microscope's ability to distinguish two separate entities as separate and distinct. Magnification and refraction are important features of microscopes, but they do not directly affect the microscope's resolving power.

Question 18

Which of the following will result when 1% to 5% agar is added to nutrient broth, boiled and cooled?

Accepted Answer

The addition of 1% to 5% agar to nutrient broth, followed by boiling and cooling, will result in a solid medium. The agar serves as a solidifying agent, turning the liquid medium into a solid, gel-like substance that is ideal for culturing microorganisms.

Question 19

Syphilis is diagnosed either with microscopy or serology because the causative agent (Treponema pallidum) does not grow on any microbiological media.Which term best describes this aspect of the T.pallidum?

Accepted Answer

T. pallidum is nonculturable which means it cannot be grown on any microbiological media. Therefore, diagnosis is based on microscopy or serology tests. The term "nonculturable" describes this aspect of T. pallidum.

Question 20

Which type of medium is able to distinguish different species or types of microorganisms based on an observable change in the colonies or in the medium?

Accepted Answer

Differential medium is specifically designed to distinguish between different species or types of microorganisms by using indicators that result in a visible change in the colonies or the medium. This visible change may include a color change, precipitation, or other observable characteristics that differentiate one type of microorganism from another. Selective, enumeration, enriched, and reducing media do not have the same capacity to distinguish between different types or species of microorganisms.

Quiz 3: Tools of the Laboratory: Methods of Studying Microorganisms