Microbiology Lab Quiz 2

Brightfield microscope

A microscope that allows light rays to pass directly to the eye without being deflected by an intervening opaque plate in the condenser

Diapraghm

Regulates the amount of light that reaches the slide

Condenser

Collects and directs the light from the lamp to the slide

Resolving power

A lens ability to completely separate two objects in a microscopic field

0.2 micrometers

Limit of resolution of light microscope

Parfocal

Microscope that maintains focus when the objective magnification is increased

Parcentral

Microscope that maintains a centrally located specimen while switching to a different objective lens

Heat fixation

Method used to kill bacteria and fix organisms to a slide

Simple staining

Use of a simple stain to color a bacterial cell

Basic dyes

Dyes that have color-bearing ionic groups that are positively charged; Ex: methylene blue, basic fuchsin, crystal violet

Acidic dyes

Dyes that have color-bearing ionic groups that are negatively charged; Ex: eosin

Morphology

Simple stain used to determine..........of bacterial cells

Bacilli

Rod shaped bacteria

Cocci

Spherical shaped bacteria

Spirals

Corkscrew-shaped bacteria

Pleomorphism

Pertains to irregularity of form, or demonstrating several different shapes

Metachromatic granules

Masses of volutin that are distinct reddish-purple granules within cells that show up when the organisms are stained with methylene blue

Palisade arrangement

Parallel arrangement of rod-shaped cells

India ink and nigrosin

Two examples of negative stains

Hans Christian Grams

Danish physician that certain stains were retained by some types of bacterial cells, but removed from others during the staining process; developed gram-staining

treatment

For a physician, a Gram stain of a specific specimen may be used to determine a(n)............

Differential Stain

Staining reactions that take advantage of the fact that cells or structures within cells display dissimilar staining reactions that can be distinguished by the use of different dyes--example is a gram stain

Primary Stain

The original stain used; will color the gram-positive bacteria; crystal violet

Mordant

Substance that combines with a dye or stain and thereby fixes it in a material; iodine

Decolorizer

Substance that only affects gram-negative cells; alcohol

Counterstain

Substance that colors gram-negative cells, but does not affect gram-positive cells; safranin

Peptidoglycan

Comprises the cell wall of bacteria and is important in Gram staining, distinguishes between gram positive and negative

Decolorization

The most critical step in the Gram staining procedure

Endospores

Structures that allow certain bacteria to survive environmental conditions that are not favorable for growth; genera Bacillus and Clostridia

Exosporium

Protein coat around endospores that form a protective barrier

Autoclave

Machine that produces the proper conditions needed to kill endospores

Mycolic Acid

A waxy, cell wall material in bacteria such as mycobacterium; prevents bacteria from being stained routinely; acid-fast stain

Blue

Color non-acid fast bacteria appear after undergoing acid-fast staining

Carbol-fuschin

Primary stain in acid-fast stain

Green

Color spores appear after spore staining

Thermoduric

Bacteria that can that can survive high temperatures and cause spoilage and souring in foods

Membrane filter method

Reliable procedure for determining coliforms in water

Coliforms

Gram-negative, facultative anaerobes that live in the intestines of animals