I want to apologize first for asking this, But I want to know if any of you know about bacterial growth media.Nutrient agar media when used as a growth medium for Pseudomonas aeruginosa during incubation for more than 24 hours, about 2 days, when viewed again, the results were that the nutrient agar media became slightly darker (became black) And the colonies that were originally white become slightly brownish. Has it been contaminated? I need help for this. Thank you🙏🏻

If the whole plate changes colour, it is more likely some kind of component in there. Whether that is likely or expected depends on the medium, of course. Often, metals can be involved. Darkening of bacterial colonies can also caused by metals or by pigments such as melanin.

If you have bacterial or fungal contamination you would see them on growing on the plates (which is kind of the point of agar plates in the first place).

On 6/10/2022 at 11:43 PM, CharonY said:

If the whole plate changes colour, it is more likely some kind of component in there. Whether that is likely or expected depends on the medium, of course. Often, metals can be involved. Darkening of bacterial colonies can also caused by metals or by pigments such as melanin.

If you have bacterial or fungal contamination you would see them on growing on the plates (which is kind of the point of agar plates in the first place).

thank you so much for ur explaning Mr. CharonY, fortunately yesterday i've checked again my plates it still a bit darkening/brownish colour on my nutrient agar media and yes there is no fungal or other bacteria on it, and on my MHA media that i used for checkin bacterial inhibiton of pseudomonas turned into greenish. it's a relief that my plates did not get any contamination. Thank you once again