Microbiology lab test

• They can be used to view living organisms. 
• Motility can be viewed.
• Because they are not heat fixed; grouping of oragnisms is not disturbed.

• 1) Using pipet, place small drop of the liquid to be viewed in the center of a slide.
• 2) Place cover slip over the drop, making sure it is droped at 45 deg angle and not straight down to avoid air bubbles.

• 1) hold slip cover with the fingers of one hand.
• 2) with pipet place very small drop on slip cover.
• 3) quickly invert slip cover over the depression of a depression slide.

• Because of increased contrast microbes are easier to see.
• Because a cover slip is not used, oil immersion can be used increasing the magnification.
• Stained slides can be saved for future observation.

• Because the microbes must be heat affixed to the slide which kills the microbes motility can not be seen.
• The natural arrangment of bacteria will be disrupted as a result of the preparation of the slide.

• Make sure you are using a clean slide
• If microbes are settled to the bottom of the tube gently agitate the tube shaking it from side to side not up and down.
• Spread a loop full of broth about the size of a dime on the middle of the slide.
• Air dry the slide never use the burner to dry.
• Heat fix the slide by passing through the cone tip of the blue flame 3 times.

• place a small drop of water on the slide.
• remove the bacteria from the slant and spread them in the water to the size of a dime.
• air dry
• heat affix

• place a few drops of metholyne blue over the smear and wait one minute.
• holding the slide angled down over the sink slowly run water over it.
• blot the slide with bulbous paper

• get the bateria focused with the high-dry objective.
• rotate objectives to in between high dry and oil immersion.
• place a drop of immersion oil directly over condenser.
• rotate immersion objective into place.
• adjust the fine adjustment to focus.
• after use discard slide into container on the counter.
• clean objective with immersion oil cleaner and lens paper a few times.

a simple stain cannot differentiate between different bacteria and a differential stain can

to differentiate between different bacterias

• 1 cover the smear with crystal violet wait 1 min rinse and shake. 
• 2 cover the smear with grams iodine wait 1 min rinse and shake 
• 3 cover smear with denatured alcohol wait 15 secs rinse and shake
• 4 cover the smear with safranin wait 1 min rinse and shake

• crystal violet - primary stain
• grams iodine - mordant (reinforces attachment to cell wall)
• ethonol - decolorizer
• safrinin - counter stain

it could expierience grams variabilty where a slide appears to have both gram positive and gram negative. A heavy smear will also interupt the decolorizing step causing gram neg bacteria to appear gram pos.