Lab Quiz 1 Flashcards by Rene Galindo

Where is the stage, nose piece, course focus, eye piece, and fine focus

3-1 Microscopy

Stage- Where slide sits
Nose piece - Rotating lenses
Course focus - Moves stage up and down quickly
Eye piece - Adjustable to eye width
Fine focus - Smaller stage movements to get clear focus

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What are the four names of the lenses?

3-1 Microscopy

Scanning
Low power
High power
Oil immersion lens

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What is the ocular magnification, object magnification, and total magnification

3-1 Microscopy

Ocular magnification is 10x for the microscope
Object magnification can be adjusted to 4x,10x, 40x, and 100x
Total mag. = ocular x object. therefore 40x, 100x, 400x, 1000x

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What is oil immersion?

3-1 Microscopy

Oil has similar refraction to glass and helps focus light through lens
Must only be used on 100x and NOT 40x

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What is aseptic technique? What is innoculation?

1-3 Aseptic Technique

Aseptic technique is when bacteria is transfered without contamination
Innoculation is the introducing of microorganisms to the environment

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Outline the steps involved in a slant culture.

1-3 Aseptic Technique

Sterilize innoculation loop with burner
Flame the tube’s lip and when loop cools pass wire over growth
Flame tube and streak sterile agar surface in a zig zag pattern
Flame tube and innoculation loop

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What is a chromagen and what are it’s two components?

3-5 Simple Stain

Colored molecule to increase visibility on slide
Auxochrome is the charged portion allowing binding
Chromophore is colored portion

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What are four examples of Basic stains? What is their charge?

3-5 Simple Stain

Methylene Blue
Crystal violet
Safranin (red-pink)
Malachite green (teal)
(+)

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What is the purpose of a streak plate?

1-4 Streak Plate

Identify what bacteria are in a sample
Allows us to isolate colonies of bacteria

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What is the purpose of a negative stain?

3-6 Negative Stain

(-) charge repels (-) of cell resulting in outlining the morphology, arrangement, and cell size

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Why is the negative stain medically important?

3-6 Negative Stain

Some bacteria can only be seen with negative stain (spirochetes)

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What is the charge of Negative dyes? Give 4 examples.

3-6 Negative Stain

Negative charge to repel from cell’s charge
Congo Red
Nigrosin (black)
India Ink
Eosin

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What is the purpose of a capsule stain?

3-9 Capsule Stain

Identify capsule producing cells and non encapsulated cells

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What are stains? What do they consist of?

3-5 Simple Stain

Stains are solutions that help make transparent cytoplasm and organelles visible
Solutions consisting of a solvent and colored molecule

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What is a chromophore? An auxochrome? What kind of charge does the auxochrome have in basic stains?

3-5 Simple Stain

Chromophore - Portion of chromagen that gives color
Auxochrome - Charged portion of chromagen
Basic charges (+) are attracted to cell surface (-)

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Why are most bacteria most easily stained by basic stains (hint: think about the charges)?

3-5 Simple Stain

Most cells have a negative charge. Thus a basic charge (+) is attracted to the charge of bacteria

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Name 3 common basic stains.

3-5 Simple Stain

Methylene Blue
Crystal Violet
Safranin

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List 3 reasons for heat-fixing bacterial smears.

3-5 Simple Stain

Kills bacteria
Causes adhesion to slide
Coagulates cytoplasm proteins increasing visibility

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Why is it usually necessary to stain bacterial cells in order to see them?

3-5 Simple Stain

Bacterial cells have transparent cytoplasms and by staining you can see cytoplasm as well as organelles

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In the medical laboratory, bacterial characteristics such as morphology and arrangement are usually determined by a _____________ stain.

3-5 Simple Stain

Gram

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What is wrong with the heat-fixing technique illustrated on pg 186?

3-5 Simple Stain

Allow the flame to completely pass through the flame and cool off on the other side. do not swipe it through the fire quickly.

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Why do we use a needle when making a smear from slant culture instead of using a loop?

3-5 Simple Stain

Allows for more precise culture collection and avoids getting too much sample.

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How does the chromogen in a negative stain differ from the chromogen in the simple stain?

3-6 Negative Stain

Negative stain has (-) charge that creates an outline to be able to see morphology, arrangement, and cell size. Chromagen in a simple stain has a positive charge that attaches to bacteria and stains them.

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The chromogen in a negative stain carries a ___________ charge. Is the negative stain, acidic or basic?

3-6 Negative Stain

Study These Flashcards

Negative
Negative stain is acidic

Why do the bacterial cells remain unstained in a negative stain? ## Footnote 3-6 Negative Stain

- The similar charges makes the stain repel from the cell

Two stains often used in negative staining are ________________ and ____________________. ## Footnote 3-6 Negative Stain

- Congo Red - Nigrosin

Negative stains are used to determine ____________________ and _______________________ in bacteria that are: ## Footnote 3-6 Negative Stain

- Morphology - Arrangement and cell size - Fragile and heat sensitive

A spirochete that is usually stained by a negative stain is ___________________________. This organism causes the disease __________________________. Another spirochete is ______________________________, which causes the disease _________________________. ## Footnote 3-6 Negative Stain

- Treponema pallidum - Syphilis (STI) - Borrelia burgdorferi - Lyme disease

Why are negative stains used when determining the accurate size of a micro-organism is crucial? ## Footnote 3-6 Negative Stain

Heat fixing can result in microorganisms shrinking. Negative staining does not

In a good negative stain, what should the background of the slide look like? ## Footnote 3-6 Negative Stain

Uniformly dark

Simple stains stain the __________________ and not the _________________; negative stains stain the ______________________ and not the ________________________. ## Footnote 3-6 Negative Stain

- Microorganism - Background - Background - Microorganism

What is wrong with the amount of acidic dye that the pg 192 recommends that you use? How much dye should you use? ## Footnote 3-6 Negative Stain

A whole drop was used. A half drop can be used by touching the dropper to the slide.

Differential stains allow a microbiologist to: ## Footnote 3-7 Gram Stain

Differentiate gram (+) and gram (-) bacteria

Which are used more frequently, differential stains or simple stains? ## Footnote 3-7 Gram Stain

Differential Stains are used 95% of the time

The most commonly used differential stain in bacteriology is the _______________ stain. ## Footnote 3-7 Gram Stain

Gram

Besides the gram stain, other differential stains test for the presence of _____________, _____________, _________________, or __________________ in bacteria. ## Footnote 3-7 Gram Stain

- Acid-fastness - Capsule - Spores - Flagella

In the gram stain a _____________________ step occurs between the application of two ___________ stains. ## Footnote 3-7 Gram Stain

- Decolorization - Basic

The primary stain in the gram stain is _____________________. What do bacterial cells look like after application of this primary stain? ## Footnote 3-7 Gram Stain

- Crystal violet - Purple

Iodine acts as a ___________________ in the gram stain. What is the purpose of adding iodine? ## Footnote 3-7 Gram Stain

- Mordant - Binds negative charge to positive charge of crystal violet allowing more purple to stay on the cells

The most critical step in the gram stain is the ______________________ step. ## Footnote 3-7 Gram Stain

Decolorization

The decolorizing solution we use in the gram stain is _______________________________. ## Footnote 3-7 Gram Stain

Acetone Alcohol

In the last step in the gram stain, gram negative cells are colored by safranin, which is a ____________________________. ## Footnote 3-7 Gram Stain

Red (basic) counterstain

The ability to resist or not resist decolorization in the gram stain is based on: ## Footnote 3-7 Gram Stain

Composition of the cell wall in Gram positive and Gram negative cells

What do gram negative and gram positive cells look like before crystal violet is added in the gram stain? ## Footnote 3-7 Gram Stain

They are transparent

What do gram negative and gram positive cells look like after the mordant is added in the gram stain? ## Footnote 3-7 Gram Stain

- Gram positive cells will look purple - Gram negative cells will be red - Over exposure results in redish gram positive cells - Underexposure results in purple gram negative cells -Red bc iodine as safranin hasn't been added yet

What do gram negative cells look like after the decolorization step in the gram stain? Why? ## Footnote 3-7 Gram Stain

They will appear transleucent because both the crystal violet and iodine will have been washed off.

What do gram positive cells look like after the decolorization step in the gram stain? Why? ## Footnote 3-7 Gram Stain

They will look purple because the crystal violet and iodine would have stained the cells and remained attached after the wash.

What will happen to gram negative cells if you don’t add enough alcohol in the gram stain? ## Footnote 3-7 Gram Stain

They will maintain a red hue from the iodine

What will happen to gram positive cells if you add too much alcohol in the gram stain? ## Footnote 3-7 Gram Stain

The gram positive cells will become more red in addition to purple giving poor visibility

Why is it best to use cultures that are 24 hours old or less for gram staining? ## Footnote 3-7 Gram Stain

Bacillus and Staphylococcus can lose the crystal violet-iodine complex in more than 24 hours

Name 3 Gram negative bacterial genera and 2 Gram positive bacterial genera other than the genera used in this exp. ## Footnote 3-7 Gram Stain

Gram Negative: - Eschericha coli - Citrobacter freundii - Klebsiella pneumoniae Gram Positive: - Staphylococcus aureus - Streptococcus pyogenes

What do the gram negative cells look like after successful completion of the gram stain? Gram positive cells? ## Footnote 3-7 Gram Stain

- Gram positive cells will be purple - Gram negative cells will be pink

Why are you asked to gram stain a mixture of gram positive and gram negative bacteria on the same slide? ## Footnote 3-7 Gram Stain

To create clear contrast between gram positive and gram negative bacteria

Why do you need a counterstain in the gram stain? ## Footnote 3-7 Gram Stain

1. Crystal violet attaches to both gram positive and negative cells 2. Mordant fixes crystal violet onto gram **positive** cells 3. Acetone alcohol Washes the crystal violet off gram **negative** cells 4. Saffranin **is then used to stain gram negative cells to provide visual contrast as the gram positive cells remain purple while the gram positive cells become pink**

Why do gram-negative bacteria stain differently than gram-positive bacteria in the gram stain? Be specific! ## Footnote 3-7 Gram Stain

Gram Positive: - Thick Peptidoglycan layer - Crystal violet is retained by PG layer with the help of mordant even after acetone alcohol wash Gram Negative: - Thin Peptidoglycan layer - Lipid A dense layer - Crystal violet is washed out by acteone alcohol due to thinner PG and Lipid A layer - Safranin is then used to stain the transparent gram negative cells

What is the Optic lense? What is the objective lense? ## Footnote 3-1 Microscope

Optic Lens - Where your eyes go Objective lens - Lenses on the nose piece

What are teichoic acids? ## Footnote 3-7 Gram Stain

- Unique to gram positive bacteria - Teichoic acids are supporting structures embedded in the PG layer of gram positive bacteria

What is the charge of an auxochrome in a simple stain? What about a negative? ## Footnote 3-6 Negative Stain

- In a simple stain an auxochrome would be basic and therefore have a positive charge - In a negative, an auxochrome would be acidic and therefore have a negative charge

Which is easier to get antibiotics for, gram positive or negative bacteria? ## Footnote 3-7 Gram Stain

- Harder for gram negative as meds struggle to pass lipid A layer - Most medicine is water based and cannot cross the lipid layer

Lab Quiz 1 Flashcards

(59 cards)