Micro Lab midterm

5 I's of Microbiology

Inoculation, Incubation, Isolation, Inspection, Identification

Inoculation

Introducing microorganisms into culture media

Incubation

Growing microorganisms under suitable conditions

Isolation

Separating microorganisms into pure cultures

Inspection

Observing characteristics of microbial growth

Identification

Determining the identity of a microorganism

Culture medium

Nutrient material used to grow microorganisms

Inoculum

Microorganisms introduced into media to begin growth

Sterile

Free of microorganisms

General purpose media

Media that supports growth of many different microorganisms

Examples of general purpose media

Nutrient agar, Nutrient broth, TSA

Enriched media

Media containing special nutrients for fastidious organisms

Examples of enriched media

Blood agar and Chocolate agar

Fastidious organism

Organism requiring special nutrients to grow

Selective media

Media that inhibits some microorganisms while allowing others to grow

Keywords for selective media

Inhibit, Restrict, Isolate

Differential media

Media that distinguishes microorganisms based on visible reactions

Keywords for differential media

Detect, Distinguish, Determine, Identify

Liquid media

Media without solidifying agents

Example of liquid media

Nutrient broth

Semi-solid media

Media containing a small amount of agar

Example of semi-solid media

Motility medium

Solid media

Media containing enough agar to remain solid

Example of solid media

Nutrient agar

Agar

Seaweed-derived solidifying agent used in microbiological media

Gelatin

Collagen-derived solidifying agent that can be broken down by bacteria

Function of agar

Solidifies media for bacterial growth

EMB agar

Selective and differential medium used for Gram-negative rods

EMB selects for

Gram-negative bacteria

EMB differentiates

Lactose fermentation

E. coli appearance on EMB

Green metallic sheen with dark purple-black colony

Green metallic sheen indicates

Strong lactose fermentation by E. coli

PEA agar

Selective medium for Gram-positive bacteria

PEA allows growth of

Gram-positive bacteria

PEA inhibits

Gram-negative bacteria

MSA

Mannitol Salt Agar

MSA is

Selective and differential

Why is MSA selective?

High salt concentration

MSA selects for

Staphylococci

MSA differentiates

Mannitol fermentation

Mannitol fermentation positive result

Yellow media

Mannitol fermentation negative result

Red or pink media

MacConkey agar

Selective and differential medium

MacConkey selects for

Gram-negative bacteria

MacConkey differentiates

Lactose fermenters from non-lactose fermenters

Lactose fermenter on MacConkey

Pink to red colonies

Non-lactose fermenter on MacConkey

Colorless colonies

Bacterial colony

Visible mass of growth originating from a single bacterial cell

Colony morphology

Macroscopic appearance of a colony

Six characteristics of colony morphology

Pigmentation, Form, Margin, Elevation, Texture, Size

Pigmentation

Color of a colony

Positive pigmentation

Any color other than white, beige, or off-white

Negative pigmentation

White, beige, or off-white colony

Circular colony

Round colony with even borders

Irregular colony

Colony with asymmetrical shape

Filamentous form

Colony with thread-like extensions

Rhizoid form

Colony with root-like extensions

Spindle form

Long, thin colony shape

Entire margin

Smooth colony edge

Undulate margin

Wavy colony edge

Lobate margin

Edge with deep lobes

Erose margin

Serrated colony edge

Filamentous margin

Thin thread-like projections

Curled margin

Circular rings resembling tree rings

Flat elevation

Colony level with agar surface

Raised elevation

Colony above agar with even height

Convex elevation

Colony with slightly elevated center

Pulvinate elevation

Colony with highly elevated center

Umbonate elevation

Colony with raised center and flatter edges

Smooth texture

Even colony surface

Rough texture

Uneven colony surface

Mucoid texture

Slimy appearance

Dry texture

Crusty appearance

Opaque colony

Cannot see through colony

Translucent colony

Light passes through colony

Punctiform colony

Tiny dot-like colony

Uniform growth

Growth evenly distributed throughout broth

Floccular growth

Floating clumps in broth

Sedimentary growth

Growth at bottom of broth

Pellicle growth

Growth on surface of broth

SIM stands for

Sulfide, Indole, Motility

Purpose of SIM test

Differentiates enteric bacteria based on sulfur reduction, indole production, and motility

Positive sulfur reduction

Black precipitate formation

Black precipitate indicates

Hydrogen sulfide production

Positive indole test

Red or pink ring after Kovac's reagent

Kovac's reagent

Reagent used to detect indole production

Positive motility result

Growth spreading away from stab line

Motile bacteria in SIM

Produce cloudy growth throughout medium

Starch hydrolysis test

Detects production of amylase

Amylase

Enzyme that breaks down starch

Iodine作用 in starch test

Turns starch blue-black

Positive starch hydrolysis

Clear halo around bacterial growth

Negative starch hydrolysis

Blue-black color right up to the colony

Clear zone around colony

Amylase is present

Fermentation

Breakdown of carbohydrates producing acids and sometimes gas

Sugars commonly tested

Glucose, Lactose, Sucrose

Positive carbohydrate fermentation

Yellow broth

Yellow broth indicates

Acid production from fermentation

Negative carbohydrate fermentation

Blue broth

Blue broth indicates

No fermentation, protein breakdown