Chapter 3 Tools of the Laboratory: The Methods for Studying Microorganisms

Question 1

ability to enlarge objects extent of enlargement is the

Answer 1

Magnification

Question 2

ability to show detail

Answer 2

Resolving power

Question 3

The objective lens forms the magnified ___________

Answer 3

real image

Question 4

The real image is projected to the ocular where it is magnified again to form the ____________

Answer 4

virtual image

Question 5

______________ of the final image is a product of the separate magnifying powers of the two lenses

Answer 5

Total Magnification

Question 6

The capacity to distinguish or separate two adjacent objects and depends on
The wavelength of light that forms the image along with characteristics of the objectives

Answer 6

Resolution

Question 7

of lens ranges from 0.1 to 1.25
Shorter wavelength and larger numerical aperture will provide better resolution

Answer 7

Numerical apertur

Question 8

most widely used; specimen is darker than surrounding field; used for live and preserved stained specimens

Answer 8

Bright-fiel

Question 9

brightly illuminated specimens surrounded by dark field; used for live and unstained specimens

Answer 9

Dark-field

Question 10

transforms subtle changes in light waves passing through the specimen into differences in light intensity, best for observing intracellular structures

Answer 10

Phase-contrast

Question 11

Modified microscope with an ultraviolet radiation source and filter.

Uses dyes that emit visible light when bombarded with shorter UV rays - fluorescence

Useful in diagnosing infections

Answer 11

Fluorescence Microscope

Question 12

Uses a laser beam of light to scan the specimen.

Integrates images to allow focus on multiple depths or planes.

Answer 12

Scanning Confocal Microscope

Question 13

Forms an image with a beam of electrons that can be made to travel in wavelike patterns when accelerated to high speeds

Electron waves are 100,000 times shorter than the waves of visible light

Electrons have tremendous power to resolve minute structures because resolving power is a function of wavelength

Magnification between 5,000X and 1,000,000X

Answer 13

Electron Microscopy

Question 14

transmit electrons through the specimen. Darker areas represent thicker, denser parts and lighter areas indicate more transparent, less dense parts.

Answer 14

Transmission electron microscopes

Question 15

provide detailed three-dimensional view. SEM bombards surface of a whole, metal-coated specimen with electrons while scanning back and forth over it.

Answer 15

Scanning electron microscopes

Question 16

allow examination of characteristics of live cells: size, motility, shape, and arrangement

Answer 16

Wet mounts and hanging drop mounts –

Question 17

are made by drying and heating a film of specimen. This smear is stained using dyes to permit visualization of cells or cell parts.

Answer 17

Fixed mounts

Question 18

Dyes are used to create contrast by imparting color

Answer 18

Staining

Question 19

cationic, positively charged chromophore

Answer 19

Basic dyes

Question 20

surfaces of microbes are negatively charged and attract basic dyes

Answer 20

Positive staining

Question 21

anionic, negatively charged chromophore

Answer 21

Acidic dyes

Question 22

microbe repels dye, the dye stains the background

Answer 22

Negative stainin

Question 23

one dye is used; reveals shape, size, and arrangemen

Answer 23

Simple stains

Question 24

use a primary stain and a counterstain to distinguish cell types or parts (examples: Gram stain, acid-fast stain, and endospore stain)

Answer 24

Differential stain

Question 25

reveal certain cell parts not revealed by conventional methods: capsule and flagellar stains

Answer 25

Structural stains

Question 26

If an individual bacterial cell is separated from other cells and has space on a nutrient surface, it will grow into a mound of cells— a colony. A colony consists of one species.

Answer 26

Isolation

Question 27

If a single species is growing in the container, you have a pure culture but if there are multiple species than you have a mixed culture. Check for contaminants (unknown or unwanted microbes) in the culture.

Answer 27

Inspection

Question 28

Cell and colony morphology or staining characteristics DNA sequence Biochemical tests to determine an organism’s chemical and metabolic characteristics Immunological tests

Answer 28

Ways to Identify a Microbe:

Question 29

liquid, semisolid, and solid

Answer 29

Physical state

Question 30

synthetic (chemically defined) and complex

Answer 30

Chemical composition

Question 31

general purpose, enriched, selective, differential, anaerobic, transport, assay, enumeration

Answer 31

Functional type

Question 32

broth; does not solidify

Answer 32

Liquid

Question 33

contains solidifying agent

Answer 33

Semisolid

Question 34

firm surface for colony formation Contains solidifying agent Liquefiable and nonliquefiable

Answer 34

Solid

Question 35

The most commonly used solidifying agent Solid at room temperature, liquefies at boiling (100oC), does not re-solidify until it cools to 42oC Provides framework to hold moisture and nutrients Not digestible for most microbes

Answer 35

Agar

Question 36

liquid medium containing beef extract and peptone

Answer 36

Nutrient broth

Question 37

solid media containing beef extract, peptone, and agar

Answer 37

Nutrient agar

Question 38

contains pure organic and inorganic compounds in an exact chemical formula

Answer 38

Synthetic

Question 39

contains at least one ingredient that is not chemically definable

Answer 39

Complex or nonsynthetic

Question 40

grows a broad range of microbes, usually nonsynthetic

Answer 40

General purpose media

Question 41

contains complex organic substances such as blood, serum, hemoglobin, or special growth factors required by fastidious microbes

Answer 41

Enriched media

Question 42

contains one or more agents that inhibit growth of some microbes and encourage growth of the desired microbes

Answer 42

Selective media

Question 43

allows growth of several types of microbes and displays visible differences among those microbes

Answer 43

Differential media:

Question 44

contains a substance that absorbs oxygen or slows penetration of oxygen into medium; used for growing anaerobic bacteria

Answer 44

Reducing medium

Question 45

– contains sugars that can be fermented, converted to acids, and a pH indicator to show this reaction

Answer 45

Carbohydrate fermentation medium