26/01/2022
🔶Why petri dishes inverted during incubation??🔶
🔴1-When the plates are incubated in the normal position, water evaporation from media occurs.
These vapours condense on the lid of the petri dishes and drops fall on the colonies developed on the media surface.This cause colony mix-up with each other and spread through out the plate surface.This creates the problem in counting and proper determination of microbial count.
🔴2-The evaporation of water from media can cause media dryness that can affect the microbial growth but when the plates are incubated in an inverted position, the rate of evaporation decreases that results in proper microbial growth.
🔴3-The lid of petri dishes may contain any contamination that spreads on the media and grows with the sample microbes.This may create an error in microbial count determination.
🔴4-It is easy to handle the inverted petri dishes because the lid of the petri dish may open during handling when incubated in normal position and it may cause contamination from air.
For best practise:
*We label the petri dishes at the bottom part because lid may exchange with other petri dishes creating confusion and inverted position makes it easy to read the labeling of petri dishes.
