Agar plate discoloration


Hello! I am currently a student doing a research paper about using weak organic acids as preservatives and microbial growth inhibition so I did an experiment. However, I got a small problem where there was no growth on the plates and instead a weird discoloration as showed in the picture. I don’t know if this is some sort of microorganism or if it the acids that caused the discoloration.

I was wondering how I should write about it in the discussion and what the cause is. Thank you in advance.

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Esraa 2021-02-15T16:42:54+00:00 1 Answer 29 views 0

Answer ( 1 )


    It seems like if the discoloration of agar is caused by the contaminating bacteria ( useless bacteria ) then you can counter-check its probability by growing its discolored agar area on a new agar plate. If the color appears again without any unnecessary growth then it means this is because of an inorganic acid preservative, but if the growth occurs then the answer will be clear .

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