Microbiology Lab Practical 1 Flashcards
What ingredient is added to nutrient broth to make it solidify?
Agar
Resolving power
Ability to completely separate two objects in a microscopic field.
D=lambda divided by NA
D is limit of resolution
Lambda is wavelength used to observe specimen
NA is numerical aperture
What temp. And pressure are things autoclaved?
121degrees Celsius
15min
15 psi of steam pressure
What temp does agar melt?
100 degrees Celsius
What temp does agar solidify?
45 degrees Celsius
Why are plates incubated upside down
Because if they aren’t then condensation from the dish lid will be deposited on the agar surface, allowing organisms to swim and preventing the formation of individual colonies
When would you use a negative stain?
When studying morphology of bacterial cells and characterizing some of the external structures, such as capsules, that are associated with bacterial cells
Useful for accurately determining cell dimensions
Useful for observing spirochaetes, which tend to be very thin cells that do not readily stain with pos
What dye do you use for neg staining and is it neutral, acidic, or basic
Nigrosin
Acidic
Three basic dyes/stains
Methylene blue
Basic fuchsin
Crystal violet
One acidic dye
Eosin
Types of cocci
Diplococci and tetrads
Streptococci
Staphylococci
Types of Rods(bacillus)
Coccobacillus
Bacilli
Fusiform
Simple stain definition
Use of a single stain to color a bacterial cell
Why are slides heat fixed prior to staining? 2reasons
- Cause them to adhere to slide
2. Preserve the structural integrity of the cells
Reagents used in a capsule stain
Congo red
Manevals stain
How to calculate the scale of a drawing
Scale= drawing size/ actual size
Types of molecules that may be found in a capsule
glycocalyx
Poly-D-glutamic.
Difference between gram pos and neg
Pos- purple
Neg- pink
Stains used during gram staining lab and what they do
Crystal violet- primary stain
Grams iodine- mordant. Combines with crystal violet to form insoluble complex with pos.
Alcohol or acetone- decolorization. Pos will retain purple, but dye mordant is removed from neg leaving it colorless.
Safranin- counterstain. Colors gram neg. pink/ red
Gram pos cell wall vs gram neg cell wall
Pos- thick peptidoglycan. Little phospholipid membrane inside
Neg- outer membrane, peptidoglycan, then phospholipid membrane
Gram pos bacterium
Staphylococcus epidermidis
Gram neg bacterium
Pseudomonas fluorescens
Who do bacteria form spores?
It allows them to survive environmental conditions that are not favorable for growth
Name a genus of a spore forming bacterium
Bacillus
Reagents of schaeffer Fulton spore stain
Malachite green
Safranin
Reagents in acid stain fast
Basic-fuchsin
Acid-alcohol
Methylene blue
Purpose of acid fast stain
It is a diagnostic tool
Name one acid fast bacterium
Tuberculosis
