Chapter 2 Flashcards by Alyssa Leach

How are microorganisms collected?

From environment: soil, water

From clinical specimens: blood, cerebrospinal fluid, sputum, urine, feces, diseases tissue

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What are the five I’s of microbiology?

Inoculation
Incubation
Isolation
Inspection
Identification

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What is inoculation?

The implantation of microorganisms into or onto culture media

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What is incubation?

Media containing inoculates are placed in temperature controlled chambers (20-40C)

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What happens during incubation?

Microbes grow and multiply, producing visible growth in the media

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What is isolation?

A cell separated from other cells on a nutrient surface, it will form a colony

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What is a colony?

A macroscopic cluster of cells appearing on a solid medium arising from the multiplication of a single cell

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What does isolation require?

medium with a firm surface
petri dish
inoculating tools

Ex) streaking

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What is inspection and identification?

Microbes can be identified thru

microscopic appearance
characterization of cellular metabolism
genetic and immunological characteristics

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What is a culture?

A propagation of microorganisms with various media

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What is a medium?

A nutrient used to grow microorganisms outside their natural habitat

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What are the physical states of media?

liquid
semisolid
solid (can convert to liquid)
solid (can’t convert to liquid)

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Semisolid is to test for?

Motility

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What are the different types of media?

Chemically defined(recipe)
Complex media (don’t know every ingredient)
Selective media
Differential media

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What is chemically defined media?

Media whose composition are precisely chemically defined
contain organic and inorganic compounds
molecular content specified by a specific formula(recipe)

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What is complex media?

contains at least 1 ingredient that is not chemically definable
extracts of animals, plants, or yeast
blood, serum, meat extracts, or infusions

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What is selective media?

Contains one or more agents that inhibit the growth of a certain microbes but not others

-important when isolating a specific type of microorganism from samples containing dozens of species

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What is differential media?

Allows multiple types of microorganisms to grow but are designed to display differences among those microorganisms

-it shows variations in colony size or color, media changes color, formation of gas bubbles or precipitates

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What are methods for isolating bacteria?

Streaking
Dilution
Spread plate

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What does the objective lens do?

Closest to the specimen, forms the initial image called the real image

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What does the ocular lens do?

Forms the second image called the virtual image that will be received by the eye and converted to the retinal and visual image

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What is oil immersion lens?

uses oil to capture light that would otherwise be lost to scatter
liquid bends light onward towards lens

What does reducing scatter do?

Increases resolution

What is light field microscopy?

Light shining from under

What is dark field microscopy?

Light shining from side (makes background dark)

What is phase contrast microscopy?

See outside structures of the cell better and can move light source wherever

What is confocal microscopy?

Adding dyes and bacteria will light the bacteria up while the background is dark

What is electron microscopy?

Shows intense detail

Preparing specimens depends on what?

Condition of specimen, aims of the examiner, types of microscopy available

What mounts allow you to observe as near to the natural habitat state as possible?

1. Wet mount | 2. Hanging drop

What is a wet mount?

Consists of a drop or two of culture placed on a slide and overlaid with a cover slip

What is a hanging drop?

A drop of culture is placed in a concave slide, Vaseline adhesive or sealant, and cover slip are used to suspend the sample

What do short term mounts assess?

Size, shape, arrangement, color, and motility

What are permanent mounts?

Smear technique, stains

Who developed the smear technique?

Robert Koch

What is smear technique?

Spread a thin film made from a liquid suspension of cells on a slide, air dry, heat fix: heat gently to kill the specimen and attach to the slide

What dye has a positive charge?

Basic dyes

What dye has a negative charge?

Acidic dyes

Bacteria attract what dye?

Basic dyes even tho they attract negatively charged substances

Negative vs positive staining

Positive: dye sticks to the specimen and gives it color Negative: does not stick to the specimen but settles distance from its outer boundary, forming a silhouette

Simple vs differential staining

Simple: only require a single dye, causes all the cells in the smear to appear more or less the same color regardless of type, reveals shape, size, and arrangement Differential: uses 2 colored dyes; primary and counter stain, distinguish cell types or part, more complex and require additional chemical reagents to produce the desired reaction

What are the type of differential stains?

1. Gram stain 2. Acid fast stain 3. Endospore stain

What is the most important differential stain?

Gram stain

Who developed the gram stain?

Hans Christian Gram

What does the gram stain consist of?

Crystal violet(primary stain), iodine(the mordant), alcohol rinse(decolorizer), safranin(counterstain)

What is a practical aid in diagnosing infection and guiding drug treatment?

Gram stain

What is acid fast stain?

Differentiates acid fast bacteria (pink) from non acid fast bacteria (blue)

What stain detects Mycobacterium tuberculosis?

Acid fast stain

What is endospore stain?

Similar to acid fast stain in that a dye is forced by heat into resistant bodies called spores or endospores

What does endospore stain distinguish?

Spores and vegetative cells

What are the special stains?

Capsule staining and flagellar staining

What is capsule staining?

- used to observe the microbial capsule, an unstructured protective layer surrounding the cells of some bacteria and fungi - neg. stained with India ink

What is flagellar staining?

- used to reveal tiny, slender, filaments used by bacteria for locomotion - flagellar are enlarged by depositing a coating on the outside of the filament and then staining it

What are the types of electron microscopy?

1. Scanning =surface ( low powered) | 2. Transmission=internal