Agar PlatesAgar Plates

By: Kristin CangaMatt Hanchey

B NelsonStephanie Slagle

By: Kristin CangaMatt Hanchey

B NelsonStephanie Slagle

Why Use Agar Plates?Why Use Agar Plates?

To obtain single isolated colonies of microorganisms.

The isolated colonies will allow you to observe specific characteristics such as colony size, shape and color.

To obtain single isolated colonies of microorganisms.

The isolated colonies will allow you to observe specific characteristics such as colony size, shape and color.

Types of MediaTypes of Media

Enriched Media: Are a basic nutrient media with extra nutrient added such as blood serum or egg. The blood agar and chocolate agar are examples of this media.

Selective Media: Contain antibacterial substances such as bio-salt or antimicrobials which inhibit or kill all but a few types of bacteria. MacConkey agar is a type of this media.

Differential Media: Allow bacteria to be differentiated into groups of bio-chemical reactions on the media..

Enrichment Media: Are liquid media that favor growth of a particular group of organisms. They contain nutrients that either encourage drugs of the desired organisms or contain inhibitory substances that suppress competitors. Selenite Broth is an example of this media.

Enriched Media: Are a basic nutrient media with extra nutrient added such as blood serum or egg. The blood agar and chocolate agar are examples of this media.

Selective Media: Contain antibacterial substances such as bio-salt or antimicrobials which inhibit or kill all but a few types of bacteria. MacConkey agar is a type of this media.

Differential Media: Allow bacteria to be differentiated into groups of bio-chemical reactions on the media..

Enrichment Media: Are liquid media that favor growth of a particular group of organisms. They contain nutrients that either encourage drugs of the desired organisms or contain inhibitory substances that suppress competitors. Selenite Broth is an example of this media.

Types of Agar PlatesTypes of Agar Plates

Types vary depending on what you are trying to culture. There are many different types of Agar plates Blood Agar: Contain blood cells from an animal (e.g.

sheep). Most bacteria will grow on this medium. MacConkey Agar: Is an agar that is specific to Gram-

negative bacteria growth. Tryptic Soy Agar: Is a basic medium that is used for

culturing many kinds of microorganisms. It is mainly used as an initial growth medium for the purposes of observing colony morphology, and achieving sufficient growth for further biochemical testing; as well as for culture storage.

Types vary depending on what you are trying to culture. There are many different types of Agar plates Blood Agar: Contain blood cells from an animal (e.g.

sheep). Most bacteria will grow on this medium. MacConkey Agar: Is an agar that is specific to Gram-

negative bacteria growth. Tryptic Soy Agar: Is a basic medium that is used for

culturing many kinds of microorganisms. It is mainly used as an initial growth medium for the purposes of observing colony morphology, and achieving sufficient growth for further biochemical testing; as well as for culture storage.

Materials you will need:Materials you will need: Gloves Inoculating loop OR sterilized wooden sticks for

streaking Permanent marker or grease pencil to label your plates

beforehand Bunsen burner or sterilizing heater if intending to

sterilize the inoculating loop between streaks Swab for collecting the primary inoculum, if intending to

collect bacteria from an environmental source Agar plate Incubator, if incubating at a controlled temperature,

such as 37 ｡C. However, many common microbial species will grow on plates left at room temperature, through their growth may be slower than if the plates were incubated at 37 ｡C

Antibacterial soap to wash your hands 5% bleach solution to clean your work area when

finished.

Gloves Inoculating loop OR sterilized wooden sticks for

streaking Permanent marker or grease pencil to label your plates

beforehand Bunsen burner or sterilizing heater if intending to

sterilize the inoculating loop between streaks Swab for collecting the primary inoculum, if intending to

collect bacteria from an environmental source Agar plate Incubator, if incubating at a controlled temperature,

such as 37 ｡C. However, many common microbial species will grow on plates left at room temperature, through their growth may be slower than if the plates were incubated at 37 ｡C

Antibacterial soap to wash your hands 5% bleach solution to clean your work area when

finished.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Touch your inoculating loop (sterile swab, or sterile stick as shown in the picture) to the material you want to spread.

Go back and forth a number of times in a small area of the Agar plate.

The goal is to spread your material completely over this inital area of the plate.

Step One:(The Primary Streak)

If you are right-handed, hold the plate in your left hand, and the inoculating loop in your right - as through you would a paint brush. If you are left-

handed, use the opposite hands.

Step Two:(The Secondary Streak)

Sterilize your inoculating loop, or use a fresh, sterile inoculating stick or swab. Make sure the loop is cool before your next streak. If

you were to use the original loop, you will not be diluting the individual microbes you applied in the first streak.

Step Two:(The Secondary Streak)

Sterilize your inoculating loop, or use a fresh, sterile inoculating stick or swab. Make sure the loop is cool before your next streak. If

you were to use the original loop, you will not be diluting the individual microbes you applied in the first streak.

Pick up the plate and rotate it 1/4 of a turn to your left (if right-handed), or to your right (if left handed).

Run the loop through the previous streak 2-3 times, then draw it along 1/3 of the remaining plate, as shown by the blue line in the image.

Pick up the plate and rotate it 1/4 of a turn to your left (if right-handed), or to your right (if left handed).

Run the loop through the previous streak 2-3 times, then draw it along 1/3 of the remaining plate, as shown by the blue line in the image.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Step Three:(The Tertiary Streak)

Rotate the plate another 1/4 turn and sterilize yourinoculating loop or take a fresh, sterile stick or swab. Again, make sure to cool your

loop between streaks.

Step Three:(The Tertiary Streak)

Rotate the plate another 1/4 turn and sterilize yourinoculating loop or take a fresh, sterile stick or swab. Again, make sure to cool your

loop between streaks.

Run the loop through the previous, secondary streak 2-3 times, and draw the streak over a remaining 1/3 of the plate, as shown.

Run the loop through the previous, secondary streak 2-3 times, and draw the streak over a remaining 1/3 of the plate, as shown.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Step Four:(The Quarternary Streak)

Rotate the plate another 1/4 turn and sterilize the inoculating loop.

Again, cool the loop between streaks, or use a new sterile swab.

Step Four:(The Quarternary Streak)

Rotate the plate another 1/4 turn and sterilize the inoculating loop.

Again, cool the loop between streaks, or use a new sterile swab. Run the loop through the previous tertiary streak 2 times and draw over the remaining free space in the plate, being careful not to contact the primary streak (yellow).

Run the loop through the previous tertiary streak 2 times and draw over the remaining free space in the plate, being careful not to contact the primary streak (yellow).

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

IncubationIncubation

Incubate your plates for 18 - 24 hours to see what you’ve grown!

Sources: www.madsci.org

Incubate your plates for 18 - 24 hours to see what you’ve grown!

Sources: www.madsci.org