Chapter 2: Tools of the Laboratory

Question 1

The Five I’s

Answer 1

Inoculation Incubation Isolation Inspection Identification

Question 2

Culture

Answer 2

the propagation of microorganisms with various media

Question 3

Medium

Answer 3

a nutrient used to grow microorganisms outside their natural habitat

Question 4

Inoculation

Answer 4

the implantation of microorganisms into or onto culture media

Question 5

Usual incubation temperatures

Answer 5

between 20°C and 40°C

Question 6

Pure Culture

Answer 6

container of medium that grows only a single known species

Question 7

Mixed Culture

Answer 7

Contains two or more identifiable species

Question 8

Contaminated Culture

Answer 8

Was once pure or mixed, but has since been contaminated; can’t identify all the organisms

Question 9

Physical States of Media

Answer 9

liquid semisolid solid (can be converted to liquid) solid (cannot be liquefied)

Question 10

Agar

Answer 10

complex polysaccharide from the alga Gellidium; liquefies at 100°C and solidifies at 42°C and can be poured in liquid form that will not harm the microbe or the handler

Question 11

General Purpose Media

Answer 11

Grows a broad spectrum of microbes; complex; Nutrient agar, broth, brain-heart infusion, & TSA

Question 12

Selective Media

Answer 12

Contains one or more agents that inhibit growth of certain microbes but not others; for samples containing dozens of different species (saliva, skin, water, soil)

Question 13

Enriched Media

Answer 13

Contains complex organic substances; for growing certain species (fastidious microbes); Blood agar, Chocolate agar

Question 14

Differential Media

Answer 14

Allows multiple types of microorganisms to grow; causes different reactions (dyes make microorganisms easily identifiable)

Question 15

Transport Media

Answer 15

Used to maintain and preserve specimens that have to be held for a period of time before clinical analysis; also used to sustain species that die quickly

Question 16

Reducing Media

Answer 16

Contains sodium thioglycollate or cystine that absorbs oxygen or slows the penetration of oxygen; grows anaerobic bacteria or determines oxygen requirements of isolates

Question 17

Carbohydrate Fermentation Media

Answer 17

Contains sugars that can be fermented (converted to acids) and a pH indicator to show this reaction; identifies bacteria and fungi

Question 18

Streak Plate

Answer 18

Easy and effective; method of choice

Question 19

Loop Dilution

Answer 19

Allows colonies to grow deep in the solution, not just on the surface

Question 20

Viruses measurements

Answer 20

between 20 – 800 nm

Question 21

Smallest bacteria measurements

Answer 21

200 nm

Question 22

Protozoa and Algae measurements

Answer 22

3-4 mm

Question 23

Objective Lens

Answer 23

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

Question 24

Ocular Lens

Answer 24

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

Question 25

Resolution

Answer 25

the capacity of an optical system to distinguish or separate two adjacent objects or points from one another.

Question 26

Human eye can resolve objects that are no closer than___________apart

Answer 26

0.2 mm

Question 27

Oil Immersion Lens

Answer 27

uses oil to capture light that would otherwise be lost to scatter which in turn increases resolution; oil immersion lens can resolve images that are at least 0.2 μm in diameter and at least 0.2 μm apart

Question 28

Bright-field Microscope

Answer 28

Forms its image when light is transmitted through the specimen; produces image that is darker than the surrounding illuminated field.

Question 29

Dark-field Microscope

Answer 29

Puts a “block” on a bright-field microscope that blocks all light from entering the objective lens except peripheral light; creates image of brightly illuminated specimens surrounded by a dark field

Question 30

Phase-Contrast Microscope

Answer 30

Transforms subtle changes in light waves passing through specimen into differences in light intensity (different parts of specimen have different densities); best for internal detail

Question 31

Interference Microscope

Answer 31

Manipulates light like phase-contrast but adds contrasting colors to the image and two beams of light rather than a single one; produces extremely well-defined images that are vividly colored and appear 3-D

Question 32

Fluorescent Microscope

Answer 32

Modified compound microscope with an Ultraviolet radiation source and a filter that protects the viewer’s eye; specimen must be coated with a source of fluorescence

Question 33

Confocal Microscope

Answer 33

Overcomes problem of cells or structures being too thick causing microscopes to have trouble focusing; Uses a laser beam of light to scan various depths in the specimen; captures highly focused view at any level

Question 34

Transmission Electron Microscope

Answer 34

Produces image by transmitting electrons through the specimen; specimens must be sectioned in extremely thin slices and stained or coated with metals

Question 35

Scanning Electron Microscope

Answer 35

Bombards surface of a whole metal-coated specimen with electrons while scanning back and forth over it; electron pattern is displayed on a TV screen; color is added afterwards

Question 36

Wet Mount

Answer 36

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

Question 37

Hanging Drop

Answer 37

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

Question 38

Purpose of short term mounts

Answer 38

provide a true assessment of size, shape, arrangement, color, and motility

Question 39

Steps in Smear Technique

Answer 39

(1) spread a thin film made from a liquid suspension of cells on a slide (2) air dry (3) heat fix: heat gently to kill the specimen and attach to the slide

Question 40

Basic dyes have a ________ charge

Answer 40

positive

Question 41

Acidic dyes have a ________ chage

Answer 41

negative

Question 42

Positive Stain

Answer 42

dye sticks to the specimen and gives it color

Question 43

Negative Stain

Answer 43

does not stick to the specimen but settles some distance from its outer boundary, forming a silhouette

Question 44

Simple Stain

Answer 44

only require a single dye and an uncomplicated procedure; causes all the cells in the smear to appear more or less the same color, regardless of type; reveal shape, size, and arrangement

Question 45

Differential Stain

Answer 45

use two differently colored dyes: the primary dye and the counterstain

Question 46

Crystal Violet

Answer 46

Primary Stain in Gram Staining

Question 47

Iodine

Answer 47

The mordant in Gram Staining

Question 48

Alcohol Rinse

Answer 48

the decolorizer in Gram staining

Question 49

Safranin

Answer 49

the counterstain in Gram staining

Question 50

Gram-Positive Color

Answer 50

Blue/purple

Question 51

Gram-Negative Color

Answer 51

Pink/red

Question 52

Acid Fast Stain

Answer 52

differentiates acid-fast bacteria (pink) from non-acid-fast bacteria (blue)

Question 53

Endospore Stain

Answer 53

Forced by heat into resistant bodies called spores; distinguishes between spores and vegetative cells

Question 54

Capsule Stain

Answer 54

used to observe the microbial capsule, an unstructured protective layer surrounding the cells of some bacteria and fungi

Question 55

Flagellar Stain

Answer 55

flagella are enlarged by depositing a coating on the outside of the filament and then staining it