CHAPTER 3 GUIDE Flashcards
What are the 3 Isolation techniques?
- Streak plate method 2. Loop dilution, or pour plate, technique 3. Spread plate technique
What is the Streak plate method?
a small droplet of sample is spread with a tool called an inoculating loop over the surface of the medium according to a pattern that gradually thins out the sample and separates the cells spatially over several sections of the plate.
What is the Loop dilution, or pour plate, technique?
the sample is inoculated, also with a loop, into a series of cooled but still liquid agar tubes so as to dilute the number of cells in each successive tube in the series.
What is the Spread plate technique?
a small volume of liquid from a diluted sample is pipetted onto the surface of the medium and spread around evenly by a sterile spreading tool (sometimes called a “hockey stick”).
What are the 7 different types of stains?
- Gram staining 2. Acid-fast stain 3. Endospore stain (spore stain) 4. Structural stains 5. Structural stains 6. Capsule staining 7. Flagellar staining
What is Gram staining?
It is an important diagnostic staining technique for bacteria.
What is an Acid-fast stain?
It is another commonly used differential stain. This stain originated as a specific method to detect Mycobacterium tuberculosis in specimens.
What is an Endospore stain (spore stain)?
It is similar to the acid-fast method in that a dye is forced by heat into resistant survival cells called spores or endospores formed in response to adverse conditions.
What are Structural stains?
They are used to emphasize special cell parts such as capsules, endospores, and flagella that are not revealed by conventional staining methods.
What is Capsule staining?
It is a method of observing the microbial capsule, an unstructured protective layer surrounding the cells of some bacteria and fungi.
What is Flagellar staining?
It is a method of revealing flagella, the tiny, slender filaments used by bacteria for locomotion.
What are the 4 processes of Gram staining?
- crystal violet (the primary dye) 2. Gram’s iodine (IKI, the mordant) 3. an alcohol rinse (decolorizer) 4. contrasting counterstain?usually, the red dye, safranin.
Describe the step by step flow of light through a microscope to create image.
- Magnification in most microscopes results from a complex interaction between visible light waves and the curvature of the lens. 2. When a beam or ray of light transmitted through air strikes and passes through the convex surface of glass as the bending or change in the angle of the light ray as it passes through a medium such as a lens. 3. When an object is placed a certain distance from the spherical lens and illuminated with light, an optical replica, or image, of it is formed by the refracted light.
What are the 5 main parts of a microscope that affect the image?
- Lamp filter 2. Iris diaphragm 3. Condenser 4. Objective lens 5. Ocular lens
What is the purpose of lamp filter in the microscope?
The light formed by the lamp is directed through it.
What is the purpose of iris diaphragm in the microscope?
It is the opening before the condenser which receives the light from the lamp filter.
What is the purpose of condenser in the microscope?
It gathers the light rays and focuses them into a single point on the specimen.
What is the purpose of objective lens in the microscope?
It is where the image is formed.
What is the purpose of ocular lens in the microscope?
This is where the image is projected, which forms a final magnification.
Why do we need to culture microbes?
In some ways, culturing microbes is analogous to gardening. Cultures are formed by “seeding” tiny plots (media) with microbial cells.
Differentiate between magnification and resolution.
Magnification is the ability to make objects appear enlarged while Resolution is the capacity of a microscope lens system to accurately distinguish between two separate entities that lie close to each other
Describe how the numerical aperture related to resolution.
The other factor influencing resolution is the numerical aperture (NA), a mathematical constant derived from the physical structure of the lens. This number represents the angle of light produced by refraction and is a measure of the quantity of light gathered by the lens.
Describe how the wavelength related to resolution.
The wavelength of light is an important factor in the resolution of a microscope. Shorter wavelengths yield higher resolution. The greatest resolving power in optical microscopy requires near-ultraviolet light, the shortest effective visible imaging wavelength.
Why do we use oil for oil immersion lenses?
We need oil immersion lenses to maximize its resolving power. This transmits a continuous cone of light from the condenser to the objective, thereby increasing the amount of light and, consequently, the numerical aperture. Without oil, some of the peripheral light that passes through the specimen is scattered into the air or onto the glass slide; the scattering decreases resolution.
