Microbiology Lab Exam # 2- 2023/ 57
Questions and solved Answers/
Verified.
Mycolic acid - -Bacteria such as mycobacterium and nocardia have cell walls with a high
lipid content. One of the cell wall lipids is a waxy material. This material is a complex
lipid that is composed of fatty acids and fatty alcohols that have hydrocarbon chains up
to 80 carbons in length.
It significantly affects the staining properties of these bacteria and prevents them from
being stained by many of the stains routinely used in microbiology.
-Aseptic technique - -The purpose of this technique is to insure that no contaminating
organisms are introduced into culture materials when the latter are inoculated or
handled in some manner. It also insures that organisms that are being handled do not
contaminate the handler or others who may be present.
-Robert Koch - -The father of medical microbiology. One of the first to recognize that if
he was going to prove that a particular bacterium causes a specific disease, it would be
necessary to isolate the agent from all other bacteria and characterize the pathogen.
From his studies on pathogenic bacteria, his laboratory contributed many techniques to
the science of microbiology, including the method for obtaining pure cultures of
bacteria.
-Pure culture - -Contains only a single kind of organism.
The purpose of this is to study the cultural, morphological, and physiological
characteristics of an individual organism.
, Two commonly used procedures are the streak plate and pour plate. Both procedures
involve diluting the bacterial cells in a sample to an end point where a single cell divides.
-Pure colony - -The colony is assumed to be the identical progeny of the original cell
and can be picked and used for further study of the bacterium.
-Smear preparation - -Virtually all staining procedures depends upon this preparation.
Goals of a successful preparation:
1. Cause the cells to adhere to the microscope slide so that they are not washed off
during subsequent staining and washing procedures.
2. Insure that shrinkage of cells does not occur during staining, otherwise distortion and
artifacts can result.
3. A thin preparation is ideal because the thickness will determine if you can visualize
individual cells, their arrangement, or details regarding micro-structures associated
with cells.
To enhance the contrast of bacterial cells so they can be visualized with a brightfield
microscope.
-Simple staining - -The use of a single stain to color a bacterial cell. Can be used to
determine the morphology of bacterial cells.
-Basic dyes - -Dyes used for simple staining are methylene blue, basic fuchsin, and
crystal violet. They have color-bearing ionic groups (chromophores) that are positively
charged (cationic).
They work well with bacterial cells that have chemical groups on their surfaces that
confer a net negative charge to the cell. Therefore, there is a pronounced electrostatic
attraction between the cell and the cationic chromophore of the stain.
Questions and solved Answers/
Verified.
Mycolic acid - -Bacteria such as mycobacterium and nocardia have cell walls with a high
lipid content. One of the cell wall lipids is a waxy material. This material is a complex
lipid that is composed of fatty acids and fatty alcohols that have hydrocarbon chains up
to 80 carbons in length.
It significantly affects the staining properties of these bacteria and prevents them from
being stained by many of the stains routinely used in microbiology.
-Aseptic technique - -The purpose of this technique is to insure that no contaminating
organisms are introduced into culture materials when the latter are inoculated or
handled in some manner. It also insures that organisms that are being handled do not
contaminate the handler or others who may be present.
-Robert Koch - -The father of medical microbiology. One of the first to recognize that if
he was going to prove that a particular bacterium causes a specific disease, it would be
necessary to isolate the agent from all other bacteria and characterize the pathogen.
From his studies on pathogenic bacteria, his laboratory contributed many techniques to
the science of microbiology, including the method for obtaining pure cultures of
bacteria.
-Pure culture - -Contains only a single kind of organism.
The purpose of this is to study the cultural, morphological, and physiological
characteristics of an individual organism.
, Two commonly used procedures are the streak plate and pour plate. Both procedures
involve diluting the bacterial cells in a sample to an end point where a single cell divides.
-Pure colony - -The colony is assumed to be the identical progeny of the original cell
and can be picked and used for further study of the bacterium.
-Smear preparation - -Virtually all staining procedures depends upon this preparation.
Goals of a successful preparation:
1. Cause the cells to adhere to the microscope slide so that they are not washed off
during subsequent staining and washing procedures.
2. Insure that shrinkage of cells does not occur during staining, otherwise distortion and
artifacts can result.
3. A thin preparation is ideal because the thickness will determine if you can visualize
individual cells, their arrangement, or details regarding micro-structures associated
with cells.
To enhance the contrast of bacterial cells so they can be visualized with a brightfield
microscope.
-Simple staining - -The use of a single stain to color a bacterial cell. Can be used to
determine the morphology of bacterial cells.
-Basic dyes - -Dyes used for simple staining are methylene blue, basic fuchsin, and
crystal violet. They have color-bearing ionic groups (chromophores) that are positively
charged (cationic).
They work well with bacterial cells that have chemical groups on their surfaces that
confer a net negative charge to the cell. Therefore, there is a pronounced electrostatic
attraction between the cell and the cationic chromophore of the stain.
