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microbial culture

One of the diagnostic methods of microbiology and it is used to determine the cause of an infectous disease by allowing the microorganism to multiply in certain specific media under controlled lab conditions.


contains nutrients for growth of microbes.


visible mass of microorganisms growing on a solid medium; in general it is formed from reproduction of a single cell so that all the members of a colony are desendant from that original cell

mixed culture

two or more kinds of microbial species are found

pure culture

one kind of microbial species is found

stock culture

a culture of a microorganism maintained solely for the purpose of keeping the organism in a viable condition by subculture into fresh medium

selective medium

allows the growth of certain kinds of bacteria while inhibiting the growth of others

differential medium

allows you to differentiate microbes based on thier metabolic activity

Types of differential Mediums

Blood Agar, gelatin, SIM Tubes, Simmons Citrate

Types of Selective Medium

Sabouraud Dextrose

Both Selective & Differential Medium

Kligler Iron Agar, Mac Conkey Agar, Mannitol Salt Agar

Neither Selective nor Differential

Mueller-Hinton Agar, Nutrient Agar

total Magnification

determined by multiplying the eye piece power (usually 10x) by the objective lens in place. EX. a 10x eyepiece and a 4x objective yields a total magnification of 40x

working distance

distance between the objective lens and the specimen. At low mag the working distance is longer


specimens that appear in focus or centered in the field of view at one magnification level will also appear centered when mag level is changed


cloudiness of broth


cottony or wooly masses floating in broth


"skin" that forms on the surface of a broth culture

primary stain

Stains what you want to see;crystal violet


sets dye; fixes crystal violet to cell wall;iodine


makes cells or structures more visible;safranin

Why is a dilution series often done before making colony counts?

By diluting it becomes easier to identify viabile colonies when using streak plate method.
Determining # of organisms in original culture
# if colonies x plating dilution factor x tube dilution factor

What is meant by "Zone of Inhibition"?

The area on an agar plate where growth of a control organism is prevented by an antibitic, usually placed on the agar surface. If the organism is suseptible to the abntibiotic there will not be growth where the anitibiotic is.

For what reasons might a chemical that is usually thought to be a good antimicrobial show no zone of inhibition?

• They have acquired antibiotic resistance
• The antibiotic disk isn't carefully pressed down enough into agar plate before being inverted and incubated

Why is it important for many of the media used this semester to set up a negative control tube?

For the comparison to see exactly what and how much growth.

How would you test for the ability of a microbe to produce catalase?

Use loop to transfer some growth from bacteria to a clean microscope slide. Use sterile dropper to apply several drops of hydrogen peroxide to bacteria. Bubbling indicates the release of oxygen gas and a positive reaction for the enzyme catalase

What medium is used to test for hemolysis?

Blood Agar
Hemolysis destroys red blood cells

What chemical is added to starch plates to test for reaction?


What is enzyme that breaks down starch?


Gram positive


Gram Negative


Basic Shape of bacteria

coocus, rod(bacillus), and spiral

Basic Shape of Endospore


Basic Shape of Algea on wet mount


Basic Shape of Aspergillus


Basic Shape of Penicillium

skeleton fingers

Basic Shape of Rhizopus

Tootsie Pop

Basic Shape of Plasmosium

circle, crescent, sausage shaped

Basic Shape of Trypanosoma


Basic Shape of Balantidium

Oval (kind of flask shaped)

Process used to grow lytic phages

Pour mixture of bacterial stock, viral dilution, and soft agar over agar plate. These mixtures solidify and are then incubated.

Voges-Proskauer Test

Mixes with reagants A & B after 4 days. After adding the reagants look closely for color change which indicates acetoin production.

Heat fix

Pass slide through flame 3 times.

obligate aerobes

Must have oxygen in order to breakdown organic molecules for energy


Microbes that can produce energy through both anaerobic and aerobic . Organisms remove electrons from organic fuels and pass these electrons to other organic compounds. Final product often includes some type of acid and gas.

Faculative anaerobes

Can survive with or without oxygen

Obligate anaerobes

Can only produce energy anaerobically and oxygen is toxic

What do you use to test for motility?

SIM tube (Sulfide, Indole, Motility)


hair like structures that allow bacterial cells to attach to each other.

What are Durham tubes used for?

To test for the ability of microbes to ferment a variety of different carbohydrates.

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