Micro Lab Quiz 2

Front 1

______, or ________ charged, dyes used to stain bacteria are attracted to negatively charged cell components and stain the cell making it readily visible.

Back 1

Basic or positively charged.

Front 2

______, or _______ charged, stains are attracted to the glass slide surface leaving the bacterial in stained in a stained background.

Back 2

Acid or negatively charged stains.

Front 3

True or false: The process of fixing and staining usually kills the cell.

Back 3

True.

Front 4

________ stains use a single basic dye to increase contrast between the cell and the background.

Back 4

Simple stains.

Front 5

_________ stains are acidic dyes which color the background only and not the cell.

Back 5

Negative stains.

Front 6

_________ stains use a combination of dyes to distinguish between cells with different chemical properties.

Back 6

Differential stains.

Front 7

True or false: When creating a smear “more is better.”

Back 7

False. More is not better. The smear should be barely cloudy. If this mirror is too thick, you won’t be able to see individual cells. Solid clumps will not stain properly.

Front 8

Methylene Blue is a ______ dye, meaning it will stain what?

Back 8

Basic dye. It is positively charged and is attracted to the negatively charged cell structures. Therefore, it will stain all the cells blue.

Front 9

Nigrosin is a(n) _______ dye. It will color what?

Back 9

Nigrosin is an acidic dye and stains the background (the glass slide) and not the cells.

Front 10

What is the purpose of staining?

Back 10

To visualize cells. Bacterial cells have the same refractive index as water which makes them almost invisible when viewed under a bright field microscope. In order to increase the contrast between the cell and the background a variety of techniques can be used, usually staining!

Front 11

What is the difference between a simple stain and a differential stain?

Back 11

A simple stain uses a single basic die to increase contrast between the cell and the background. A differential stain uses a combination of dies to distinguish between cells with different chemical properties.

Front 12

What do negative staining and positive staining have in common?

Back 12

They increase the contrast between the specimen and the background.

Front 13

During staining, the slide & organism is heat fixed in order to…

Back 13

Kill the organism and attach the organism firmly to the slide.

Front 14

What cellular morphology features are observed after a simple stain?

Back 14

Cell shape and cell arrangement.

Front 15

True Or false: The purpose of simple staining is to elucidate the morphology and arrangement of bacterial cells.

Back 15

True.

Front 16

Grams bacterial stains can be characterized by the amount of _________ in the cell wall.

Back 16

Peptidoglycan.

Front 17

Gram-positive bacteria have cell walls that contain thick layers of peptidoglycan (90%). These stain _____.

Back 17

Purple.

Front 18

Gram negative bacteria have walls with thin layers of peptidoglycan, and high lipid content. These stain _______.

Back 18

Pink.

Front 19

The performance of the Gram stain on any sample requires four basic steps that include… List the steps.

Back 19

(1) apply a primary stain (crystal violet) to a heat fixed smear.

(2) add a mordant. (Grams iodine.)

(3) rapid decolorization with alcohol, acetone, or a mixture of alcohol and acetone.

(4) counterstain with safranin.

Front 20

What are the three basic morphological shapes of bacteria?

Back 20

Round shaped cells are cocci, rod shaped cells are bacilli, and spiral shaped cells are spirilla.

Front 21

Why is Gram’s iodine called a mordant?

Back 21

The iodine acts as a mordant and binds to the crystal violet.

Front 22

By omitting the iodine step in the Gram-staining procedure, what color would you expect Gram+ bacteria to stain and what color would you expect Gram- bacteria to stain?

Back 22

Gram+ : Red.

Gram- : Red.

Front 23

True or false: The Gram stain technique is based on the different structure of the cell walls of the two groups.

Back 23

True.

Front 24

Gram+ organisms contain a highly cross-linked layer of PTG that retains the primary dye, _______.

Back 24

Crystal violet.

Front 25

State 2 mistakes that you could make that would make a gram stain less reliable.

Back 25

Over-lengthy decolorization.

Putting too much dye & leaving it on too long.

Front 26

True or false: Both gram+ & gram- will be the same color purple if you forgot to use iodine.

Back 26

False.

Front 27

Why do we apply more heat in endospores stain?

Back 27

This extended heat fix is used to soften the endospore layer of keratin, to help the malachite green penetrate the endospore coat.

Front 28

What is the counter stain, primary stain, and decolorizer in that order in the endospore stain?

Back 28

Safranin, malachite green, & water.

Front 29

The endospore is ___ resistant to environmental stresses ___ the vegetative cell.

Back 29

More; than.

Front 30

Capsule stain is similar to what other staining procedure?

Back 30

Negative stain.

Front 31

A few genera of bacteria form endospores, ____ & ____.

Back 31

Bacillus & Clostridium.

Front 32

_______ are called “resting bodies” because they do not metabolize and are resistant to heat, desiccation, nutrient deprivation, extremes in temp, chemical agents including antibiotics, & ionizing radiation. They are formed when essential nutrients or water are not available.

Back 32

Endospores.

Front 33

Endospores are impermeable to most stains, so ____ is used to drive the stain into the endospore.

Back 33

Heat.

Front 34

True or false: bacterial stains are non-ionic, so neither acidic nor basic stains will adhere to their surfaces.

Back 34

True.

Front 35

True or false: endospores will easily form when the culture is growing in a fresh medium.

Back 35

False.

Front 36

Why are flagella so hard to stain?

Back 36

Flagella are so think & thread-like.

Front 37

True or false: fewer than 30 colonies on serially diluted and plated culture will give the correct estimate of colony forming units in original sample.

Back 37

False.

Front 38

What is the objective of the serial dilution method?

Back 38

To estimate the number of viable (living) cell concentration in the original sample.

Front 39

What is the objective of the serial dilution method?

Back 39

To estimate the number of viable (living) cell concentration in the original sample.

Front 40

Certain strains of bacterial species produce capsules and slime layers. These structures are composed of layers of polysaccharide or peptide covering the surface of the cell forming a viscous coat. This structure is a ______ when it is round or oval in shape & a ______ when it is irregularly shaped and loosely bound to the bacterium.

Back 40

Capsule; slime layer.

Front 41

Capsule staining is a _____ stain.

Back 41

Negative.

Front 42

To visualize flagella, we stain them. The stain coats the flagella, thereby increasing their ______.

Back 42

Diameter.

Front 43

To visualize flagella, we stain them. The stain coats the flagella, thereby increasing their ______.

Back 43

Diameter.

Front 44

2 main types of flagella: ??

Back 44

Peritrichous (all around) & polar (at one or both ends).

Front 45

(Special structures lab.) Enterobacter aerogenes or Serratia marcescens are the cultures used for _______ stain.

Back 45

Capsule stain.

Front 46

(Special structures lab.) Proteus vulgaris & Escherichia coli are used for _______ stain.

Back 46

Flagella stain.

Front 47

What type of stain is used for flagella staining?

Back 47

Leifson Flagella Stain.

Front 48

What stains are used in capsule staining?

Back 48

Copper sulfate & crystal violet.

Front 49

When endospore staining you counter stain with ____.

Back 49

Safranin.

Front 50

True of false: When capsule staining you need to heat fix your smear before you begin staining.

Back 50

False!!! Do not heat fix your capsule stain!!!

Front 51

True or false: When you are preparing your flagella stain you must heat fix your smear.

Back 51

False!!! Do NOT heat fix your smear, this will destroy the flagella structure.

Front 52

The ________ method involves applying a measured quantity of sample to a petri dish and counting the number of colonies that form. The number of colonies obtained is referred to as a(n) ______________ because only living cells are capable of reproducing and forming a colony.

Back 52

Serial dilution; viable cell count.

Front 53

(Serial dilution.) The number given by viable cell count method is called “_________”.

Back 53

Colony forming units (CFU)

Front 54

(Serial dilution.) To count individual colonies, it is necessary to have a sample with a low concentration, usually about _____ - _______ CFU/ml.

Back 54

100 - 1000.

Front 55

(Serial dilution.) on standard sized petri dishes only, plates with between ____ & _____ colonies can be counted accurately.

Back 55

30 and 300

Front 56

What type of stain is this? What kind of shape are the bacteria? What color dye is used?

Back 56

Simple stain. Rod shaped E. coli with Methylene Blue stain.

Front 57

What color/type dye is this?

Back 57

Methylene blue.

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