45 terms

Lab practical 2 study

Few questions to study for lab practical 2
In an acid fast stain, what color do non-acid-fast organisms stain?
In an acid fast stain, what color do acid-fast organisms stain?
In a Gram's stain, what color do gram+ organisms stain?
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?
nigrosin and Indian ink are used in what type of stain?
This type of stain does not penetrate the bacterial cell but rather causes the area around the cell to be dark.
What is used as a mordant in spore staining to help the uptake of the stain?
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.
The best way to determine bacterial size and cell morphology is to prepare a slide by a process called ________ staining.
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.
Some bacterial cells are surrounded by an extracellular slime layer called a ________, and staining this layer cannot be accomplished by ordinary simple staining procedures.
Capsular staining combines the methods for the simple stain and the negative stain. True or False?
Most bacteria are killed by the effects of ultraviolet light. True or False?
Bacteria that form endospores are less resistant than vegetative cells to the effects of UV light. True or False?
Ultraviolet rays can cause eye injury if looked at directly. True or False?
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?
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?
Acid-fast organisms will stain red or pink and non-acid fast organisms will stain blue.
Gram positive organisms will stain pink and gram negative organisms will stain purple.
The major organelles of motility in bacteria are:
Bacterial motility decrease with time so it is best to examine a wet mount slide immediately after it is prepared.
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:
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.
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:
__________ 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 ________
A basic dye is utilized to stain bacterial cells
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:
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.