Lab practical 2 study

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Few questions to study for lab practical 2

Blue

In an acid fast stain, what color do non-acid-fast organisms stain?

Pink

In an acid fast stain, what color do acid-fast organisms stain?

Purple

In a Gram's stain, what color do gram+ organisms stain?

Pink

In a Gram's stain, what color do gram- organisms stain?

Crystal violet, rinse, mordant of iodine, rinse with alcohol, counterstain with safranin

What is used in performing a Gram's stain?

Negative

nigrosin and Indian ink are used in what type of stain?

Negative

This type of stain does not penetrate the bacterial cell but rather causes the area around the cell to be dark.

Heat

What is used as a mordant in spore staining to help the uptake of the stain?

Safranin

Used to stain the vegetative portion in spore staining.

Malachite green

Used to stain the endospore in spore staining.

Pure culture

A culture of microorganisms in which all cells are of a single type.

Negative

The best way to determine bacterial size and cell morphology is to prepare a slide by a process called ________ staining.

Smear

Sucess at bacterial staining depends on the preparation of a suitable _______ of the organism.

To ensure shrinkage will not occur during staining, otherwise, distortion of artifacts will occur or to kill microbes.

Name one of the three goals in preparing a smear for staining.

Capsule

Some bacterial cells are surrounded by an extracellular slime layer called a ________, and staining this layer cannot be accomplished by ordinary simple staining procedures.

True.

Capsular staining combines the methods for the simple stain and the negative stain. True or False?

True.

Most bacteria are killed by the effects of ultraviolet light. True or False?

False.

Bacteria that form endospores are less resistant than vegetative cells to the effects of UV light. True or False?

True.

Ultraviolet rays can cause eye injury if looked at directly. True or False?

Mordant

The function of the ______ in Gram staining is to complex with crystal violet to form a relatively insoluble complex in the gram positive bacteria.

False. (It's gram positive that can do this).

Old cultures of gram negative bacteria can convert to gram positive or gram variable and give erroneous results. True or False?

True.

Heat is used in spore staining to enable the stain to penetrate the endospore, once there is not removed with either decolorizing agents or water. True or False?

True

Acid-fast organisms will stain red or pink and non-acid fast organisms will stain blue.

False.

Gram positive organisms will stain pink and gram negative organisms will stain purple.

Flagella

The major organelles of motility in bacteria are:

True.

Bacterial motility decrease with time so it is best to examine a wet mount slide immediately after it is prepared.

True.

Brownian movement is vibrational movement caused by invisible molecules bombarding bacterial cells.

streak plate and pour plate methods.

The two commonly used procedures to separate organisms into pure cultures are the:

True

Both the streak and pour plate methods involve diluting the number of cells in a sample.

Standard plate count (aka viable count)

The _____ is one of the most common methods for determining bacterial numbers in a sample.

Coliforms

The safety of drinking water is dependent on there being no sewage contamination. The presence of ______ in potable water suggests the potential for disease.

30 and 300

After plates are innoculated and incubated, plates that have between _______ colonies are selected for counting.

Standard plate count.

In this lab exercise, two methods are used to determine the number of bacteria present in a culture sample. Name one of them.

Discard canister

When finished with a pipette, place it in the _______which contains disinfectant.

Streak plate and pour plate

Name two commonly used procedures for obtaining pure cultures.

Pure colony

a colony that is assumed to be the identical progeny of the original cell.

Simple staining

The use of a single stain to color a bacterial cell is commonly referred to as:

Negative

__________ stains such as nigrosin and india ink do not penetrate the bacterial cell but rather cause the background area around a cell to become opaque or dark.

Capsule or glycocalyx

Some bacterial cells are surrounded by an extracellular slime layer called a ________

Simple

A basic dye is utilized to stain bacterial cells

Negative

A stain that does not penetrate cells is used to color the background.

Crystal violet or methylene blue

For the simple stain procedure, one can use:

India ink or nigrosin

For the negative stain procedure, one can use:

Air-dried

Before heat fixation, a wet smear of bacterial cells on a slide must first be:

Mycolic acid

Bacteria which contain a waxy material in their cell walls called _______ are said to be acid-fast and appear pink or red when stained.

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