quiz number 2 micro

Coccus/cocci

round

Bacillus/Bacilli

rods

Vibrio

curved rods (like comma or lima bean)

spirillum/spirilla

spirals

Spirochete

flexible spirals

single cells

photo

diplo

pairs of cells,

strepto

chain of cells,

tetrad

group of 4 cocci

sarcina

cube of cocci

staphylo

clusters of cocci

palisade/angular

bacilli side by side like a picket fence

o   Know the steps in creating a bacterial smear for bacteria on solid medium:

§  Add a small drop of water onto a slide

§  Sterilize inoculating loop and let cool for at least 10 seconds

§  Touch inoculating loop to one colony to remove a very small amount of bacteria

§  Using the inoculating loop, mix the bacteria into the drop of water on your slide and spread the water/bacteria mix out into a thin layer/film

§  Allow the slide to air dry. This can be on the slide warmer.

§  Once the slide is dry, your bacterial smear is ready to be heat-fixed.

functions of heat fixing:

§  Kills bacteria

§  Causes cells to stick to the slide

§  Causes cytoplasmic proteins to coagulate = denser cell contents so more visible

o   Know how to heat fix a slide using a Bunsen burner and a microincinerator

§  Bunsen burner: Pass slide quickly through tip of inner flame 2 to 3 times

§  Microincinerator: Hold smear in front of the opening of the microincinerator for about 5 seconds

o   Know how to sterilize an inoculating loop using a Bunsen burner:

§  Hold loop at 60 degree angle

§  Slowly pass loop through the tip of the inner cone of the flame, starting at the base of the wire and moving to the loop until each part becomes orangish-red

o   Know how to sterilize an inoculating loop using a microincinerator

§  Insert loop and wire into pre-heated microincinerator for 10 seconds and then remove

o   Allow inoculating loop to cool for 10-20 seconds after sterilizing before touching bacteria

§  If you hear a sizzling sound, the loop was not cool enough and most likely killed your cells.

Chromogen

o   colored molecule that is dissolved in a solvent to make a stain

Chromophore

portion of chromogen that gives color

Auxochrome

portion of chromogen that is charged and allows chromogen to interact with cell

o   Basic stain

§  Positively charged (cationic)

§  Positive charge is attracted to negative charge of cell wall, cell membrane, and DNA

§  Stains cells so is more commonly used

§  Examples: Methylene blue, Crystal violet, Safranin, Malachite green

Acidic stain

§  Negatively charged (anionic)

§  Negative charge is repelled by negative charge on surface of cells

§  Stains background but not cells

§  Useful for cells that distort when heat-fixed (since no heat-fixing is required) and to see capsules around cells

§  Examples: Nigrosin, Eosin

o   Know the basic procedure for staining cells using a basic stain

create a thin smear of cells on a slide, heat-fix it to the slide, and then apply the basic dye (like crystal violet or methylene blue), allowing it to bind to the negatively charged bacterial cells