Hi, recently I encountered a protocol for plating which was not the usual method I have been practicing (pour LB agar onto plate, allow it to solidify, pipette bacterial suspension onto plate, spread with hockey stick, incubate overnight). This method pipettes the bacterial suspension directly onto the empty petri dish, followed by pouring of the agar broth, then incubation). Is anyone using this method and may I have the reference for it? I also recently came across a paper (Phytochemical analysis of Andrographis paniculata extract and its antimicrobial activity) where the bacterial suspension was first mixed into the molten agar and then poured onto the plate. My question is, will the colony not form inside the agar, making counting difficult/will there be variations with the growth due to the variability of temperature of the agar?-too hot, bacteria are killed.
Would appreciate your help.
Thank you.
Hello
The method which you mentioned is called the 'pour plate' method. The advantage of using this method is that no prepared agar plates are required which is not the case with 'streak plate' method which you are using.
The disadvantage of 'pour plate' method is that on an average this method will give a lower count as heat-sensitive micro organisms may die once they come in contact with the hot agar medium.
The 'pour plate' method is often used to check bacterial contamination in food stuff.
I hope this information is helpful.
Regards.
Hi Wee Mei Yuin Joanne
Cells that do survive this method will still propagate colonies. However, they will be harder to count as rather than being on the same level as if plated on top of the agar, they will be situated in different levels inside the agar. If your current method works, then I would stick with it.
Thanks Malcolm Nobre and Jack Hopkins for the helpful information.
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