Microbio Lab Exam 1

The ability of a lens to show two adjacent objects as discrete objects.

wavelength of light and numerical aperture of the lens

• -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)

D protist

• -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

• -methylene blue
• -crystal violet
• -safranin (red)

to kill the bacteria, make them adhere to slide, and coagulate cytoplasmic proteins to make them more visible upon staining

Eosin, Nigrosin

A staining technique that allows you to see the bacteria as clear on a dark background.

the cell wall is negative and the dye is negative, so the cell repels the stain.

Because negative stains are used to study morphology and arrangement and most cells requiring negative stains are too delicate to withstand the heat.

• -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

• -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

• 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

purple/blue

reddish/pink

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.

Glycolax or slime layer composed of polysaccharides

• 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

No, because it causes the cells to shrink and the appearance of an artificial white halo that can be misinterpreted as a capsule

B) Bacillus spp; gram +

E. coli (bacillus-coccus); gram -

S. aureus, gram +

A hydrophobic molecule present in some cell walls that requires cabolfuschin to acid-fast stain it

Endospore stain

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.

They kill the bacteria

They inhibit the growth of the bacteria

A substance produced naturally by microbes (fungi)

Minimum Inhibitory Concentration; the basis quantitative measure of an antimicrobial

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

Because you do not want side effects to the host

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.

• 1) Diffusion rate of the antimicrobial
• 2) Degree of sensitivity of the microorganism
• 3) Growth rate of the bacterium

• 1) Protein synthesis
• 2) Cell wall synthesis
• 3) Folic acid synthesis
• 4) Nucleic acid synthesis

Tetracyclines

Rifampin

Sulfonamides

b-lactams penicillins

By mutation or acquiring DNA carrying a resistance gene

• 1) Altered permeability of the antimicrobial agent
• 2) Inactivation of the antimicrobial agent
• 3) Altered target site
• 4) Replacement of an antimicrobial sensitive pathway

• 1) UTI
• 2) surgical site infections
• 3) pneumonia or bloodstream infections

methicillin-resistant staphylococcus aureus; spreads quickly and is resistant to a lot of antimicrobials

Glycerol yeast extract agar - selects for growth of hyphae like soil bacteria - Actinomycetes

Nutrient Agar - grows numerous bacteria but not fungal growth

Sabouraud Dextrose Agar - selects for growth of fungi