Microbiology Chapter 3

Heat fixing a sample in microscopy is done for which purpose? A. Drying the liquid used to make the smear B. Highlighting cell structure for observation C. Simultaneously killing and securing the sample to the slide D. Preserving various cellular components in a natural state E. Making a more permanent mount for long-term study

-Simultaneously killing and securing the sample to the slide -Preserving various cellular components in a natural state -Making a more permanent mount for long-term study

How does a bacterial colony appear?

As an individual isolate on solid agar

Which one of the following is not part of the six basic techniques used to grow, examine and manipulate microorganisms in the A. laboratory? A. Inspection B. Infection C. Isolation D. Inoculation

B. Infection

Identify the selective agent in MacConkey agar that allows isolation of intestinal pathogens.

Bile salts

How much resolution can an electron microscope obtain (i.e. what can it see)?

Can see structures as small as 0.5 nm

Viruses, Rickettsia, and Chlamydia are described as obligate intracellular parasites because they can only be propagated inside living host cells. Which of the following would be appropriate for their cultivation?

Cell or tissue cultures

_________are large masses or mounds of cells, all belonging to a single type of microorganism.

Colonies or Colony

What is the typical "color" of microorganisms?

Colorless

What is the defining difference between compound microscopes and simple microscopes?

Compound microscopes have multiple lenses.

Which of the following microscopes uses a laser beam?

Confocal

Which of the following terms is used to describe a collection of bacteria growing in broth or on agar?

Culture

Media that allows the growth of multiple types of microbes but are designed to distinguish characteristics among members of the culture are called which of the following?

Differential media

Identify a medium which contains complex organic substances and/or special growth factors which allows even fastidious organisms to thrive.

Enriched medium

Which of the following reagents reacts with crystal violet as the mordant?

Gram's iodine

Which of the following six "I'"s deals with the evaluation of cultures both macroscopically and microscopically?

Inspection

_________is the ability of a microscope to make objects appear enlarged.

Magnification

_________staining involves any staining technique in which the dye actually sticks to the specimen and gives it color.

Positive Staining

At room temperature, agar will always be which of the following?

Solid

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?

The culture is contaminated.

The streak plate technique works by using an inoculating loop to spread a bacterial sample in a pattern that thins it out but this only works if which of the following is done?

The inoculating loop is re-sterilized at each thinning step of the pattern.

Why is identification of bacteria on the macroscopic appearance limited?

Very different species of bacteria may appear quite similar.

The primary purpose of staining cells on a microscope slide is to

add contrast in order to see them better

Which chemicals are used to fix microbial cells?

alcohol and formalin

______dyes have a positive charge, whereas _____dyes have a negative charge.

basic-positive charge Acidic- Negative charge

Which is a common component found in feces and, therefore, used in media to selectively culture Gram-negative bacteria?

bile salts

Also known as synthetic media, this type of media has a defined molecular content and varies very little from one source to another

chemically defined media

A common medium used for growing fastidious bacteria is?

chocolate agar.

The type of microscope in which you would see brightly illuminated specimens against a black background is

dark-field.

Staphylococcus aureus can be identified on mannitol salt agar (MSA) because it ferments the mannitol, changing the color of the agar from pink to yellow.

differntial media

Blood agar uses sheep blood to help grow fastidious microbes including streptococc.

enriched media

The ______ stain is the most universal differential staining technique for bacteria, and it differentiates bacteria based on their cell wall structure.

gram

What is the process of adding a microbe to a growth material called?

inoculation

What are the steps for microbial culture and identification in the correct order?

inoculation, incubation, isolation, inspection, identification

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

inoculation.

Different types of culture ________ provide nutrients for microbial growth.

media or Medium

A pure culture contains only

one species of microorganism

A __________ stain is one where the dye adheres to the cell whereas a __________ stain is one that colors the background surrounding the cell, leaving the cell unstained.

positive; negative

MacConkey agar isolates gram-negative enteric bacteria by inhibiting growth of gram-positive bacteria

selective media

The first microscopes were _______, meaning they contained just one magnifying lens and few working parts.

simple

_______ stains require only a single dye.

simple

Another name for chemically defined media is called _______ media.

synthetic

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

synthetic.

Please select the statement which is incorrect regarding fixed preparations.

Fixed preparations are used to view live cells.

Which of the following is an optical microscope that uses UV radiation as the illuminating source?

Fluorescence

How will E. coli appear in a Gram stain if the mordant is not applied?

Gram-negative

What is a common method for attaching bacteria to a glass slide?

Heat fixation

Which of the following determines the type of microbe at the species level?

Identification

The wavelength of light used plus the numerical aperture governs

resolution.

A microbiologist makes a fixed smear of bacterial cells and stains them with Loeffler's methylene blue. All the cells appear blue under the oil lens. This is an example of?

simple staining.

A collection of bacteria on a loop which is thinly spread across a glass slide, allowed to air-dry, and heat fixed is called a ________.

smear

Which of the following media are chemically definable?

Synthetic

General-purpose media are characterized by which of the following?

They allow the growth of a broad range of microbes.

Which describes fastidious organisms?

They require growth factors and/or complex nutrients.

Why is immersion oil often used when viewing specimens under the microscope?

To increase the resolution

True or false: All specimens are prepared in the same manner for microscopic examination.

False

True or false: Isolation of colonies usually requires a large number of cells to be inoculated over an expansive area of medium.

False

What is defined as the magnification of the ocular lens times the magnification of the objective lens?

Total magnification

What are some descriptions for basic dyes used in microbiology?

*positively charged *binds to negatively charged parts of the cell *Crystal violet is an example.

What is involved in making a smear?

- Air drying a liquid application on a glass slide - Spreading a thin film of suspended cells on a glass slide

Which of the following describes general-purpose media? (multiple answers) - They are usually nonsynthetic. - They include nutrient agar and broth. - They are usually chemically defined synthetic media. - They include Mannitol salt and MacConkey agar. - They usually contain a mixture of nutrients. - They grow a broad spectrum of microbes.

- They are usually nonsynthetic. - They include nutrient agar and broth. - They usually contain a mixture of nutrients. - They grow a broad spectrum of microbes.

To be effective, a microscope must have which of the following characteristics? A. UV fluorescence capabilities B. Adequate magnification C. Resolution D. Clarity of image

-Adequate magnification -Resolution -Clarity of image

What are considered growth factors typically added to enrich culture media.?

-Amino acids -Vitamins -Blood

Identify which of the following media are considered nonsynthetic media? -Blood agar -Minimal media for fungi -Brain heart infusion media

-Blood agar -Brain heart infusion media

Media ingredients that cannot be chemically defined include which of the following?

-Blood and serum -Cell secretions -Extracts of animals, plants, or yeasts

Media ingredients that cannot be chemically defined include which of the following? A. Blood and serum B. Disodium hydrogen phosphate C. Extracts of animals, plants, or yeasts D. Sodium chloride E. Cell secretions

-Blood and serum -Extracts of animals, plants, or yeasts -Cell secretions

What are characteristics of an enriched medium?

-Can be used to aid in the growth of fastidious organisms -May contain organic substances such as blood, serum or hemoglobin -May contain special growth factors

Negative staining of a cell can yield results concerning which of the following? A. The presence of flagella B. Cell shape and arrangement C. The type of cell wall D. The presence of a capsule E. Cell size

-Cell shape and arrangement -The presence of a capsule -Cell size

Identify disadvantages of wet mount preparations.

-Easy contamination of handler's fingers -Slide very susceptible to drying -Damage to large cells by cover glass

Identify what could potentially affect the manner in which a specimen is prepared for microscopic examination.

-If you want to observe motility -If you want to use fluorescence microscopy -If the specimen is living or preserved -If you want to see the overall structure or something specific

Identify the simple stain(s). A. Methylene blue B. Crystal violet C. Malachite green D. Gram stain

-Methylene blue -Crystal violet -Malachite green

Identify all the benefits of using solid agar compared to using liquid media.. A. Provides a firm surface on which cells can form discrete colonies B. Useful for isolating fungi C. Solid agar allows greater growth of microorganisms. D. Useful for isolating bacteria

-Provides a firm surface on which cells can form discrete colonies -Useful for isolating fungi -Useful for isolating bacteria

What describes general-purpose media?

-They usually contain a mixture of nutrients. -They are usually nonsynthetic. -They grow a broad spectrum of microbes. -They include nutrient agar and broth.

If the ocular is a 10X lens and the nosepiece objective happens to be a 10X objective, then what is the total magnification?

100x

Magnification of an object or specimen by a compound microscope occurs in how many phases?

2

What is the total magnification for a microscope when the ocular is a 10X and you are using the high power objective 40X?

400X

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

A solid medium

Which are correct regarding the six "I"s used for culturing microorganisms? A. It is important to work with a pure culture for proper identification. B. The process is a progression of steps that must be followed in order. C. The six "I"s always begin with inoculation. D. Aseptic technique should be maintained.

A. It is important to work with a pure culture for proper identification. D. Aseptic technique should be maintained.

Which of the following is not true for viruses? A. Some viruses can be grown in nutrient agar B. Cannot replicate on their own C. Must grow within a cell D. Some viruses can be grown in chicken eggs

A. Some viruses can be grown in nutrient agar

Which of the following is a macroscopic discrete cluster of cells that forms on a solid nutrient surface arising from the multiplication of a single cell?

Colony

Which term is used to describe a cluster of visible bacteria of the same species on an agar plate?

Colony

Which of the following microscope components is used to converge (or focus) the rays of light to a single point on the specimen?

Condenser

Which of the following is a medium that works by showing two reaction types, such as a color change in some colonies but not in others?

Differential medium

What staining procedures employ both a primary dye and a counterstain?

Differential stain

Which of the following microscopes uses subatomic particles, not light waves, as an illumination source to provide high magnification and high resolution?

Electron

Magnification results from the interaction of?

Light waves and lens curvature

A wet mount is suitable for observing which of the following?

Living, motile or non-motile cells

Which of the following is a vital characteristic of a reliable microscope?

Magnification

What colors represent examples of positive stains.

Methylene blue; crystal violet; safranin, malachite green

Identify the statement which accurately describes the six "I"s for the culturing of microorganisms.

Microbes must be grown in pure culture

What is absolutely true for all viruses?

Must grow in or on living cells

__________ staining is a general type of staining that does not disrupt the cell structure with heat fixation and can indicate the presence of a capsule.

Negative

Which of the following staining procedures produces a reverse image of that created by a positive stain, thus forming a silhouette around the microorganism's outer boundary?

Negative stain

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

Pour plate

Gram positive bacteria exhibit with color after the Gram-stain?

Purple

What color do Gram-negative bacteria exhibit after Gram staining?

Red

Which type of media can be used to determine if a bacteria is motile?

SIM

You are doing research on a bacterial species, trying to determine the shape, distribution, and arrangement of a number of filamentous structures that protrude from the cell surface. Which type of microscopy would best enable you to do this?

Scanning electron microscopy

Identify the method of spreading a small culture sample over a solid medium in a pattern that gradually thins out the sample resulting in isolated colonies.

Streak plate method

Microbes can be challenging to study because they often grow in complex communities and it may be difficult to separate the various species from one another to study individually. Which of the following laboratory "tools" or techniques may be of the most help with separating out different species from complex mixtures?

Use of selective agars for culture

Also known as non-synthetic media, these media cannot be chemically defined because they are partly produced from organic extracts of tissues, cells, or other biological materials.

complex media

The condenser converges (focuses) light to a single point on the specimen in a ________microscope.

compound