How to streak a plate

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How to streak a plate
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It is VERY important to use the aseptic technique
throughout this procedure
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Streak Plate

• Streak for isolated colonies
• Pure culture
• All cells came from same parental cell
• Genetic information is identical for the most
  part
• Isolated colony
• Streak plate used to get isolated colonies ? pure
  culture

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Before you start, get a bottle of O-SYL and
wipe down your bench with it
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You now will need to get an agar plate

• Notice that there are 2 slides to this plate
• You will always label the side with the agar on
  it
• This is the thicker side
• You will also always put it in the incubator with
  the agar side up

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This is a correct labeling of the plate

• You want to include the name of the agar or the
  name of the organism, the date and your initials
• Make sure to label the side of the plate that has
  the agar on it(label the plastic on the petri
  dish)
• You want your label in the corner so that you
  will be able to see the growth of your organism

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This is an INCORRECT labeling of the plate

• The name of the agar, the date and initials are
  correct
• But, the label is on the wrong side of the plate
• Do not label the lid
• It could fall off

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Make sure your lab space is set to streak a plate

• You need a plate, your culture and the flame set
  at a small level
• You also need a loop

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You are ready to begin

• Hold the culture in your right hand
• Use you right pinky to remove the cap from the
  tube
• The loop should also be in your right hand

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Always flame your tube after you open it and
before you close itDo not put the cap down on
the counter
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Keep your loop in the flame until it is red and
hot
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Remove a small amount of culture from the tube
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Put the cap back onto the tube after you have
removed a SMALL amount of culture
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You will start streaking the plate in one corner
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Flame your loop after the first streak but do not
open your culture tube again
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Turn your plate and now streak it in the opposite
direction in quadrant 2
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Flame your loop after the second streak but do
not open your culture tube again
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Continue streaking until you have streaked in 3
quadrants
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Another important point

• After flaming the loop, let it cool briefly
  before you touch any bacteria
• Otherwise, you may kill the bacteria

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Here is an animation on how to do a streak plate

• http//www.sumanasinc.com/webcontent/animations/co
  ntent/streakplate.html

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How to streak a plate

• This picture shows how to streak the plate
• Start out with a dense culture in section A and
  then BRIEFLY cross over in the different
  quadrants to dilute out the culture

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Plate A is a good example of a streak platePlate
B is a bad example of a streak plate
B
A
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Here is another example of a streak plate

• Notice at the end how there are isolated colonies