Microscope which allows light rays to pass directly from the light source through various other components of the microscope to the observers eye
characteristic of microscope design that allows changing objective lenses without significant change in position of center of field of view.
test tubes containing solid medium that has been allowed to solidify at an angle and the surface of the agar is used for the maintenance of stock cultures of microorganisms, used fro long term bacteria storage 3mo or longer,
isolation technique using a series of serial dilutions to separate CFUs, mixed with liquid agar which then solidifies
repelled from bacteria. Background in stained. Negative stains usually have a negative charge which is repelled by the negatively charged proteins on the surface of bacteria. Note: a negative stain does not mean a gram negative.
Staining procedure which causes cells to stain differently based on properties of the cell wall
has four steps. 1. Primary stain: crystalline violet that stains all bacteria purple 2. mordant: Gram's iodine sets the stain 3. decolorizer: ethanol washes out the stain from gram negative bacteria only 4. counterstain: safranin stains gram negative bacteria pink
A thin protective structure loosely bound to the cell wall that protects the cell against drying, helps trap nutrients, and sometimes binds cells together
A sticky layer that surrounds the cell wall of some prokaryotes, protecting the cell surface and sometimes helping to glue the cell to surfaces.
a thick-walled protective spore that forms inside a bacterial cell and resists harsh conditions
Under harsh environmental conditions, such as loss of a nutritional requirement, bacteria can convert from a vegetative state to THIS or a spore. THIS allows the bacteria to exist in "suspended animation"
used to stain small group of organisim that do not readily take up stain, the cell walls of these bacteria contains high concentrations of lipids, perventing uptake of dyes
Ways to prevent contamination
flame loop, inverted postition of plate, hand washing, work near bunsen burner, hold slant caps while removing sample, flame rim of slant...
Precautions used with microscope
make sure microscope is off before plug in, always start with lowest objective, carry with two hands, never use coarse adj for 40x or higher, clean lens after use of oil...
condenser should be as high, iris diaphragm should be open, immersion oil used at 100x
What is purpose of streak method?
"thin out" bacterial growth in successive sectors of a plate until individual colonies are obtained
What are the sources of contamination when transferring bacteria?
Not flaming loop, Not working near flame, touching loop to any contaminated surface while cooling
What is the purpose of heat fixing?
1. kills the bacteria 2. makes them adhere to the slide 3. coagulates their protein for better staining.
What is the primary function of the capsule?
Eliminates waste, prevents dehydration, less vulnerable to phagocytosis
What factors determine composition of a capsule?
Environment and the type of nutrients in which the bacterium is growing