Do not remove the lid unnecessarily or for prolonged periods of time. Do not lay the lid down on the counter or put the bottom of the Petri dish into the inverted lid. While inoculating the agar plate, you may either:
Set
the covered plate upside down on the counter. When you are ready to inoculate
it with the loop, lift the bottom half (with the media in it), and hold it up
vertically for a moment while streaking it. Replace it into the lid while re-flaming
the loop. Lift bottom again to continue streaking, etc.
OR
Set
the plate right side up on the counter. Lift the lid slightly ajar and hold
it at an angle, while you are streaking the plate. While this prevents contaminated
dust from falling on plate, it may be difficult to see what you are doing.
Note: Method No. 1 is recommended for examining a plate which has been incubated in an inverted position. Otherwise, water may condense on the lid and drip down onto the medium, causing the colonies to coalesce.
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