Microbiology Lab Report B

The dilution series illustrated here has been performed on a pure culture, and a 1 ml sample from each tube plated on a supportive medium. Following incubation, the plate that derived from the most dilute tube shows 50 colonies. The original culture must have had _____ cfu/ml.

5.0 X 105

Which of these is not a good reason to use agar as a solidifying agent for culture media?

Acts as a microbial nutrient

Which two of the following techniques aid in the removal of oxygen from media used to culture anaerobes?

Add reducing agents like thioglycollate Boil the medium to drive off any oxygen present

Which three of the following ingredients could be used to make defined culture media?

Ammonium sulfate Glucose Potassium phosphate

The colonies on this medium have two different morphologies. Which two of the statements below are correct about these colonies?

Both colony types illustrate a circular form. From the image, elevation cannot be determined.

Which two of the following statements regarding new approaches to culturing microbes are correct?

Co-culture of two organisms is often more successful than culturing them separately. In situ cultivation using dilute samples in an enclosure permits axenic cultures to form.

Which technique is used to increase the number of microbes with specific metabolic activities in a culture?

Enrichment culture

Which two of the following describe important limitations to the use of enrichment cultures?

Enrichment cultures are not representative of the population sampled. Enrichment cultures yield the organism that grows the fastest.

True or false: Enrichment cultures are pure cultures.

False

A method for separating cells by inoculating molten agar with the cells and then adding the agar to a sterile petri dish is plating.

Pour

Which of these is not a use of culture medium?

Reviving dead cultures

Media that allow the growth of some microbes but not others are called media.

Selective

Which technique can be used to enumerate the cells in a liquid culture?

Serial dilution

Oxygen is provided to organisms grown in laboratory culture by which two of the following methods?

Shaking flasks to provide aeration Bubbling O2 gas through the medium

"Dilution on a surface" best describes which technique?

Streak plate

Laboratory culture techniques like the use of a GasPak or anaerobic chamber are important for which of the following reasons?

The primary challenge to providing sufficient oxygen to aerobes grown in laboratory culture is that _____.

True or false: A dilution equivalent to the most dilute tube on the far right could also be achieved by two serial dilutions, each transferring 1 ml to 99 ml of saline.

True

True or false: Co-culture of a microbe of interest with plant tissue is often successful in the laboratory cultivation of some plant pathogens.

True

Which medium is not a differential medium?

Tryptic soy agar

Which two ingredients, when present, would render a bacterial medium complex?

Tryptic soy broth Yeast extract

Microbial colonies separated from each other on agar plates are each assumed to arise from _______.

a single cell

The most commonly used solidifying agent for supportive medium is .

agar

To be effective, a culture medium must contain

all nutrients required for growth

In this list of ingredients for a minimal medium used to grow Escherichia coli, the nitrogen source is _____.

ammonium sulfate

This apparatus is designed for working with microbes.

anaerobes

A pure culture is also referred to as a(n) ____ culture.

axenic

A pure culture is also referred to as a(n) culture.

axenic

The medium illustrated in this image is _____.

blood agar

Match the differential medium with the property that it can distinguish. -blood agar -MacConkey agar -mannitol salt agar

blood agar-hemolysin production MacConkey agar-acid production from lactose mannitol salt agaracid production from mannitol

Reaction of chemicals in the GasPak gas generator envelope forms _____ to fill the atmosphere of the apparatus.

carbon dioxide

Yeast extract, an aqueous extract of brewer's yeast, is often used in complex media where it provides _____. [Choose three.]

carbon sources nitrogen compounds B vitamins

A macroscopically visible cluster of microorganisms on a solid growth medium is called a(n) .

colony

In which of the following aspects of colony morphology do the two colony types illustrated here differ? yellow dots

color size

Culture media that contain ingredients of unknown chemical composition are referred to as _______.

complex

The medium tryptic soy broth, ingredients listed here, is a _____ medium.

complex

The colony elevation type depicted third from the left is _____.

convex

Which two of the ingredients in MacConkey agar are responsible for its selective nature?

crystal violet bile salts

A solid or liquid preparation used to grow, transport, and store microorganisms is termed a(n) ______.

culture medium

Culture media that contain only ingredients of known chemical composition are referred to as

defined

Culture media that contain only ingredients of known chemical composition are referred to as ______.

defined

Media used to distinguish among groups of microbes based on their reaction to the media are called media.

differential

Media used to distinguish among groups of microbes based on their reaction to the media are called ______.

differential media

The purpose of performing the streak plate technique is to _____.

dilute a culture on the surface of a medium so that single colonies form

General purpose media fortified with blood to encourage the growth of fastidious microbes are called _______.

enriched media

To increase the number of microbes with specific metabolic activities in a culture microbiologists use a technique known as culture.

enrichment

The colony margin type depicted on the far left is _____.

entire

Blood agar is an enriched medium that provides a broad range of nutrients and growth factors required for the cultivation of _____ microbes.

fastidious

In this list of ingredients for a minimal medium used to grow Escherichia coli, the carbon source is _____.

glucose

Growth of microbes on blood agar permits the distinction of _____.

hemolytic and nonhemolytic bacteria

The colony form depicted third from the right is _____.

irregular

The colony margin type depicted third from the left is _____.

lobate

The colonies that develop on this differential medium can be classified according to their ability to _____.

lyse blood cells

A liquid preparation used to supply energy and nutrients to microorganisms in the laboratory is called a culture

medium

Peptones are protein hydrolysates prepared from meat, soya, gelatin, and other proteins, and serve as sources of _____ in complex media. [Choose three.]

nitrogen carbon energy

The primary challenge to providing sufficient oxygen to aerobes grown in laboratory culture is that _____.

oxygen is poorly soluble in liquids

Which ingredient in MacConkey agar is its nitrogen source?

peptic digest

The two nitrogen sources in tryptic soy broth are

peptone tryptone

A method for separating cells by inoculating molten agar with the cells and then adding the agar to a sterile petri dish is _____.

pour plating

Peptones, a source of carbon, energy, and nitrogen in complex media, are derived from _____.

protein sources

The colony form depicted on the far left is _____.

punctiform

Oxygen is eliminated from the atmosphere in an anaerobic chamber like the one illustrated here by _____.

reacting with hydrogen to form water

Media that allow the growth of some microbes but not others are called _______.

selective media

When a microbial culture is diluted several times before plating to count the number of cells in the original sample, the technique of dilution is used.

serial

A suspension of cells is distributed over the surface of a plate with a sterile bent rod in plating.

spread

A suspension of cells is distributed over the surface of a plate with a sterile bent rod in _____.

spread plating

The method for separating cells by dragging samples over different sectors of a plate using a microbial loop is called plating.

streak

General purpose media that sustain growth of many microbes are called media.

supportive

General purpose media that sustain growth of many microbes are called _______.

supportive media

This plate can be identified as a streak plate because

the pattern of colonies illustrates the inoculation style

The colony elevation depicted on the far right is _____.

umbonate

Beef extract is an aqueous extract of lean beef and contains _____. [Choose two.]

vitamins amino acids

A user can verify the absence of oxygen in a GasPak system by inspecting the anaerobic indicator strip, shown here with a red arrow. A color of _____ on the strip indicates that the internal atmosphere lacks oxygen.

white (colorless)