CHAPTER 3 MICROBIOLOGY

6 I's

Inoculation, Incubation, Isolation, Inspection, Information Gathering, Identification

Staining

Using dyes to increase contrast and make microorganisms easier to observe

Charge of bacterial cells

Generally negative

Basic dye

Positively charged dye that stains the negatively charged bacterial cell

Acidic dye

Negatively charged dye that is repelled by bacterial cells and stains the background

Positive stain

Stains the microorganism

Negative stain

Stains the background

Simple stain

Uses one dye and shows cell shape, size, and arrangement

Differential stain

Uses multiple dyes to distinguish different cells or structures

Three differential stains

Gram stain, acid

Does Gram stain refer to charge?

No

Gram

positive color

Gram

negative color

Gram stain primary stain

Crystal violet

Gram stain counterstain

Safranin

Gram stain mordant

Iodine

Gram stain decolorizer

Alcohol

Acid

fast primary stain

Acid

fast counterstain

Acid

fast positive color

Acid

fast negative color

Endospore primary stain

Malachite green

Endospore counterstain

Safranin

Endospore color

Green

Vegetative cell color in endospore stain

Red/pink

Capsule stain

Used to visualize capsules

Pure culture

Contains one type of microorganism

Mixed culture

Contains more than one type of microorganism

Culture medium

Material providing nutrients and conditions needed for microbial growth

Liquid medium

Broth

Semisolid medium

Medium containing a lower concentration of solidifying agent

Solid medium

Medium containing enough solidifying agent to form a solid surface

General

purpose medium

Enriched medium

Provides additional nutrients for organisms with greater nutritional requirements

Selective medium

Encourages some organisms while inhibiting others

Differential medium

Allows organisms to grow but distinguishes them based on visible characteristics

MSA

Selective and differential medium; high salt selects and mannitol fermentation differentiates

Blood agar

Enriched and differential medium; can differentiate based on hemolysis

Total magnification

Objective magnification multiplied by ocular magnification

Ocular lens

Usually 10×

Scanning objective

4×

Low

power objective

High

power objective

Oil

immersion objective

40× objective with 10× ocular

400× total magnification

100× objective with 10× ocular

1000× total magnification