2nd lab exam

What is the function of the Primary stain, Mordant, Decolorizers, and Counterstains

used in the various differential stains.

What was the function of tetrazolium in the culture medium? How did it help you determine if cells were motile?

to make interpretation easier, it is motile when red is seen radiating outward from stab line

Be able to identify photomicrographs of cells with amphitrichous or peritrichous flagella arrangements

amphitrichous

Be able to identify photomicrographs of cells with amphitrichous or peritrichous flagella arrangements

petritrichous

How does the KOH test work?

gram positive has a thick peptidoglycan layer resisting; gram negative has thin layer that breaks apart

Can you explain why the KOH test produces a "snotty" liquid when Gram negative cells are placed into it and stirred?

they are being lysed due to the release of chromosomal DNA

Know the function of the reagents used in Gram Stain

(CV, I, acetone/alcohol, safranin)

initial stain, helps trap purple in cells, removes dye from peptidoglycan layer, stains colorless cells

what color are negative cells in Gram testing?

red/pink

what color are positive cells in Gram testing?

purple

what reagents are used in Gram staining

crystal violet, iodine, alcohol, safranin

Describe the function of the Congo red (negative)

stains background red, doesn't penetrate capsule

Describe the function of the Maneval's stain

stains cell body purple

Why are capsule stain cells treated differently when the smear is made – no water or heat fixing? (Capsule stain)

heat can cause cells to distort and water will rinse off cells from slide

Identify the staining reagents used in acid fast staining?

carbol fuchsin, methylene blue, decolorizer

what are the functions of reagents used in acid fast staining?

carbol fuchsin

methylene blue

decolorizer

stains cells and penetrates waxy mycolic walls (acid fast cells retain this color)

removes stain from non acid fast cells

stains non acid fast cells

What is different about acid-fast cells compared to non-acid fast cells?

acid fast cells have a waxy mycolic acid cell wall that resists colorization while non acid fast cells do not

Explain how a plaque is formed in a lawn of host cells

occurs when contiguous cells have been lysed by the virus

What is the difference between the proglottid and the scolex segments on tapeworms?

proglottid: adult body divided into segments and carried both egg and sperm

Scolex: the head that is modified with suckers, hooks used for attachment to the intestinal wall

How can bacteriophages be used to treat a disease in people that is caused by bacteria?

they infect, replicate, and lyse harmful bacteria without damaging human cells

Where do restriction enzymes come from and how do they cut DNA?

bacteria; they recognize specific specific DNA sequences and cuts DNA at those sites

What was the function of the Agarose used with the gel?

a filter that separates DNA fragments by size

What was the function of the electrophoresis buffer solution (TAE) used with the gel?

carries electrical current and keeps pH stable so DNA moves correctly

Why do smaller DNA fragments move quicker through Agarose gels?

they pass through gel pores easily

Why use heat with certain stains and not with other ones?

To help certain stains penetrate tough cell structures

How does CHROMAgar™ distinguish between the different Candida species - how is it selective and differential?

Selective: has contents to stop bacterial growth allowing fungi to grow

Differential: contains substrates that react with specific enzymes. Different speices produce different colors

identify this worm

Schistosoma male - Trematoda

identify this worm

Taenia (tapeworm) - cestode

identify this worm

Clonorchis (human liver fluke) - Trematoda

identify this worm

Fasciola (sheep fluke) - Trematoda

identify this worm

Schistosoma female - Trematoda

identify this worm

Enterobius (pinworm) - nematode

identify this worm

necator (hookworm) - nematode

identify this worm

trichinella - nematode

identify this worm

Trichinella (encysted larvae in muscle) - nematode

identify this worm

Ascaris - nematode

identify this spore

Aspergillus mycelium

identify this spore structure (Aspergillus)

condida - asexual

identify this fungus

corpinus

identify this fungus

penicillium mycelium

identify the spore structure

produces conidia; asexual

identify the spore structure

basidiospore; sexual

identify this spore structure; which is sexual, asexual?

Rhizopus - (L) asexual (R) sexual

identify this fungus

Saccharomyces

identify this spore structure

Sordaria; sexual

identify genus name and type

Balantidium coli - trophozoite

identify genus name and type

Entamoeba histolytica - (L) cyst (R) trophozoite

identify genus name and type

Giardia lamblia - (L) cyst (R) trophozoite

identify genus name

Plasmodium

identify genus name

Trypanosoma

identify genus name and type

Trichomonas vaginalis - trophozoite

How did you "enrich" for spore forming bacteria from your soil sample during the Microbe Hunt experiment?

1. Took your soil sample.

2. Suspended it in broth or water.

3. Heated the sample

4. Then plated it on agar

Identify which stain reagents are used (malachite green and safranin). What is the decolorizer?

Malachite green: primary stain

Safranin: counterstain

Decolorizer: water