The flashcards below were created by user
tasha081
on FreezingBlue Flashcards.
-
What does resolving power measure?
The ability of a lens to show two adjacent objects as discrete objects.
-
What is resolution?
wavelength of light and numerical aperture of the lens
-
What are some differences between prokaryotes and eukaryotes?
- -prokaryotes do not not have membrane bound organelles; eukaryotes do
- -prokayrotes only have a single circular chromosome
- -prokayrote ribosomes are 70S; eukaryotic ribosomes are 80S (larger)
-
A Euglena is a:
a) coccus
b) spirochete
c) fungus
d) protist
D protist
-
What is a simple stain?
- -quick way of staining most pro and eukaryotic cells
- -used to characterize a bacterial spec morphology and arrangement
- -most bacterial cells have negatively charged wall and stain is positively charged
-
What are some common basic stains?
- -methylene blue
- -crystal violet
- -safranin (red)
-
Why are basic stains heat fixed?
to kill the bacteria, make them adhere to slide, and coagulate cytoplasmic proteins to make them more visible upon staining
-
What are common acidic stains (negative)?
Eosin, Nigrosin
-
What is a negative stain?
A staining technique that allows you to see the bacteria as clear on a dark background.
-
What are the charges on a negative stain?
the cell wall is negative and the dye is negative, so the cell repels the stain.
-
Why doesnt negative stains involve heat fixing?
Because negative stains are used to study morphology and arrangement and most cells requiring negative stains are too delicate to withstand the heat.
-
What are the steps in a simple stain?
- -add sample of bacteria to slide
- -allow bacteria to dry
- -heat fix bacteria
- -cover smear with dye (meth blue, crystal violet, or safranin)
- -incubate for 5 minutes to allow organism to absorb @ room temp
- -rinse side w/ distilled water
- -blot w/ bibulous
- -observe
-
What are the steps in a negative stain?
- -Add nigrosin at one end of clean slide
- -add loop full of bacteria to stain and mix
- -take second slide and drag stain along
- -air dry and observe
-
What are the procedures for performing a gram stain?
- 1) Primary stain - crystal violet added to heat fixed sample
- 2) Iodine - mordant; enhances color of crystal violet and forms complex which is retained by thick Gram + cell wall but not Gram - wall
- 3) Decolorization - extracts dye from gram - but not gram +
- 4) Counterstain - safranin; bind to gram - cells showing up as red/pink
-
what color would a gram + cell be?
purple/blue
-
what color would a gram - cell be?
reddish/pink
-
What is the difference in composition between a gram - and gram + wall?
A gram - wall has thin layers of peptidoglycan that the alcohol creates pores in therefore releasing the crystal violet. The gram + wall has a thick layer of peptidoglycan that dehydrates and compresses in response to alcohol which traps the crystal violet thus retaining the dye and showing up as purple/blue.
-
What is a capsule composed of?
Glycolax or slime layer composed of polysaccharides
-
How is a capsule stain performed?
- 1) Bacterial cells are chemically adhered to slide
- 2) Add acidic/negative stain (congo red or nigrosin) to stain background
- 3) Add basic stain to (crystal violet or safranin) to stain cell
-
Is a capsule stain heat fixed? why?
No, because it causes the cells to shrink and the appearance of an artificial white halo that can be misinterpreted as a capsule
-

Is this:
A) K. pneumoniae
B) E. coli
C) Bacillus spp
D) S. Aureus
C) Bacillus spp; gram + (this multiple choice question has been scrambled)
-

What is shown here?
E. coli (bacillus-coccus); gram -
-

What is shown here?
S. aureus, gram +
-
What is mycolic acid?
A hydrophobic molecule present in some cell walls that requires cabolfuschin to acid-fast stain it
-
What is malachite green stain used for?
Endospore stain
-
An endospore is....
A bacterial cell that has become dormant and most dyes will not stain because it is resistant; malachite green forces the stain into the cell by steaming.
-
An antiobiotic is bactericidal if:
They kill the bacteria
-
An antimicrobial is bacteriostatic if:
They inhibit the growth of the bacteria
-
An antibiotic is:
A substance produced naturally by microbes (fungi)
-
What is MIC?
Minimum Inhibitory Concentration; the basis quantitative measure of an antimicrobial
-
What is the therapeutic index?
the ratio of the dose toxic to the host to the effective therapeutic dose. Higher index = better antibiotic.
- dose causing toxicity to 50% of the population
- --------------------------------------------------------
- min effective dose for 50% poplulation
-
Why would you want an antimicrobial with a selective toxicity towards the bacterium?
Because you do not want side effects to the host
-
What is the Kirby-Bauer test?
Test for antibiotic susceptibility. It is a disk diffusion test where zones of inhibition are measured with selective antimicrobial discs which are placed on plates of agar. Zones of inhibition are measured.
-
What are the three things that influence the zone of inhibition?
- 1) Diffusion rate of the antimicrobial
- 2) Degree of sensitivity of the microorganism
- 3) Growth rate of the bacterium
-
What are the 4 main targets that antimicrobial agents interefere with?
- 1) Protein synthesis
- 2) Cell wall synthesis
- 3) Folic acid synthesis
- 4) Nucleic acid synthesis
-
What is an antibiotic that intereferes with protein synthesis?
Tetracyclines
-
What is an antibiotic that intereferes with Nucleic acid synthesis?
Rifampin
-
What is an antibiotic that intereferes with Folic Acid
Sulfonamides
-
What is an antibiotic that intereferes with the cell wall?
b-lactams penicillins
-
How can a bacterium acquire resistance to an antimicrobial?
By mutation or acquiring DNA carrying a resistance gene
-
What are the mechanisms of bacterial resistance?
- 1) Altered permeability of the antimicrobial agent
- 2) Inactivation of the antimicrobial agent
- 3) Altered target site
- 4) Replacement of an antimicrobial sensitive pathway
-
What are the 3 most common nosocomial infections?
- 1) UTI
- 2) surgical site infections
- 3) pneumonia or bloodstream infections
-
What is MRSA and why is it so deadly?
methicillin-resistant staphylococcus aureus; spreads quickly and is resistant to a lot of antimicrobials
-
GYEA
Glycerol yeast extract agar - selects for growth of hyphae like soil bacteria - Actinomycetes
-
NA
Nutrient Agar - grows numerous bacteria but not fungal growth
-
SDA
Sabouraud Dextrose Agar - selects for growth of fungi
|
|