Microbiology Lab Practical Exam Study Guide

Round Bacterial Colony

Irregular Bacterial Colony

Filamentous Bacterial Colony

Rhizoid Bacterial Colony

Smooth Bacterial Colony Margin

Lobate Bacterial Colony Margin

Convex Colony Elevation

Umbonate Colony Elevation

Raised Colony Elevation

Pigmented Colony

COLOR

Dull Colony Surface

Shiny Colony Surface

Dry Colony Consistency

Moist Colony Consistency

Mucoid Colony Consistency

Opaque Colony

Not See Through

Translucent Colony

Sediment Growth

settlement at the bottom of the liquid media

Flocculent Growth

masses in the subsurface area of broth culture

Fine Turbidity Growth

Cloudy throughout

Broth Surface Ring

Pellicle

growth on top of broth culture

Tetrad Arrangment

in groups of 4

Sarcina Arrangement

in groups of 8

Gram Postive

Purple -- THICK cell wall

Gram Negative

Pink -- THIN cell wall

Negative Stain

stains BACKGROUND

Acid Fast Stain

Stains Fuchsia (pink)

NON ACID FAST STAIN is BLUE/GREEN

Endospore Stain

CYTOPLASM stained RED

SPORES stained DARK GREEN

Capsule Stain

Successful Streak Plate

Has Isolated Colonies

What are EMB and McConkey Agar selective for?

Gram Negative Bacteria

How does EMB agar select gram negative bacteria?

it uses eosin and methylene blue dyes to inhibit the growth of gram positive bacteria

How does McConkey agar select gram negative bacteria?

it uses blue salts and crystal violet dyes to inhibit the growth of gram positive bacteria

What are EMB and McConkey Agar differential for?

lactose and non-lactose fermenters

How does EMB agar differentiate between lactose and non-lactose fermenters?

it uses lactose as its medium and when the acid is fermented, the dyes react on the colony surface, coloring it and eosin and methylene blue inhibit gram positive bacteria

How does McConkey agar differentiate between lactose and non-lactose fermenters?

the medium contains a natural pH red dye and lactose and when lactose is fermented, the clear colonies become pink on the agar and crystal violet and bile salts inhibit gram positive bacteria

How many colonies are on a countable plate?

between 30-300 CFUs

NON-LACTOSE FERMENTERS on the EMB and McConkey agars appear ____________________.

Colorless

On EMB agar, LACTOSE FERMENTERS appear ____________________ (small and large acid production).

Metallic Green for large acid production Purple for small acid production

Beta-hemolysis (complete cell lysis)

Clearing around growth

Alpha-hemolysis (partial cell lysis)

Greening around growth

Gamma-hemolysis (no cell lysis)

No change in the medium

Positive Result For Catalase Test

Bubbles

Negative Result For Catalase Test

No Bubbles

Positive Result For Coagulase Test

Plasma forms a clot

Negative Result For Coagulase Test

Plasma remains liquid

Positive Result For Gelatin Liquidification Test

Gelatin Liquified

Negative Result For Gelatin Liquidification Test

Gelatin remained solid

What is the importance of the Coagulase Test?

It distinguishes Staphylococcus aureus from other Gram positive cocci

What is the enzyme used in the Gelatin Liquidification Test?

Gelatinase

Positive Result For Hydrolysis of Milk Protein Test

clearing around bacteria

What is the ENZYME used in the Hydrolysis of Milk Protein Test?

Casease

What is the SUBSTRATE used in the Hydrolysis of Milk Protein Test?

Casein

What does the Phenol Red Fermentation Test determine?

Whether the carbohydrate (glucose, lactose, sucrose) was fermented

Positive Result For the Phenol Red Fermentation Test

A and A/G (acid & acid/gas) = YELLOW FOR ACID PRODUCTION

Negative Result For the Phenol Red Fermentation Test

Red (No color change)

How do you know if there is acid production?

YELLOW

What is the pH Indicator used in the Phenol Red Fermentation Test?

Phenol Red

Postive Result for Starch Hydrolysis Test

clearing around the bacteria

Negative Result for Starch Hydrolysis Test

no clearing around bacteria

What is the reactant used in the Starch Hydrolysis Test to detect the presence of starch?

Gram's Iodine

Positive Motility Test

Raspberry diffuse growth extending outward from the stab line

Negative Motility Test

Raspberry colored growth along the stab line only

Positive Urease Test

Pink (Basic)

Negative Urease Test

Phase I Nitrate Reduction Test Postive Result

red

Phase I Nitrate Reduction Test Negative Result

no change

Phase II Nitrate Reduction Test Postive Result

no change

Phase II Nitrate Reduction Test Negative Result

pink

Positive Result For Sulfur Reduction Test

Black Precipitate

What is the black precipitate formed in a positive sulfur reduction test?

Ferric Sulfide

What does Blood Typing identify?

the presence of an Antigen

What is a positive result for blood typing?

(Agglutination) Clumping in the well for the antigen/antibody; Rh factor = + blood type

Mold -- MACROscopic View

hairy and fuzzy

Mold -- MICROscopic View

Yeast -- MACROscopic View

colorless and smooth -- similar to bacteria

Yeast -- MICROscopic View

bigger than bacteria and large

Euglena -- Locomotion Tool

Flagella

Euglena -- Image

green in color

Amoeba -- Locomotion Tool

Pseudopodia

Amoeba -- Image

Paramecium -- Locomotion Tool

Cilia

Paramecium -- Image

Bacterial Lawn

a thick layer of bacteria coated onto a plate

Translucent Colony

see through

Opaque Colony

not see through

Total Magnification Formula

take the power of the objective (4X, 10X, 40x, or 100x) and multiply by the power of the eyepiece, 10X

INCLUDE UNITS = x

If a microorganism is able to produce, ______________________ an exoenzyme, it can destroy the red blood cells and hemoglobin in the sheep blood present in the blood agar.

hemolysins

Catalase producing bacteria can be easily identified by using ______________________.

hydrogen peroxide

Phenol red broth is used to distinguish members of the _____________________ family.

Enterobacteriaceae (Entric) -- Found in intestinal lining

Microbes that produce the enzymes to digest carbohydrates will form various end products from pyruvate such as __________________, __________________, _________________, __________________.

acid, hydrogen gas, carbon dioxide gas or alcohol

Phenol red, the pH indicator, will turn _______________ in the presence of acid

yellow

Phenol red, the pH indicator, will turn _______________ when basic

fuchsia

The __________________ is present in order to capture any gas that might be produced during the fermentation process

Durham tube

A positive indication of gas production is a ______________ in the top of the Durham tube

bubble

Starch hydrolysis is a test that is performed in order to distinguish among bacteria that produce the enzyme ________________.

amylase

The Urease Test determines whether a microorganism can hydrolyze urea into _____________ and _______________.

ammonia and carbon dioxide

Kirby-Bauer Test

a type of antibiotic sensitivity testing used to determine the susceptibility of bacteria to various antibiotics

Zone of Inhibition

indicates the degree of sensitivity of bacteria to a drug OR the size of this zone depends on how effective the antibiotic is at stopping the growth of the bacterium