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Bacteria Changing Colour - (Jul/21/2009 )

hello everybody,
i have a bacteria that is gram negative cocci. special thing about it is that it changes colour with growth, means growing freshly on nutrient agar its Red and then turns Cream colour with time, but again it is Red at the outer ends of colony means where it has access to media and growing fresh there,
So can anybody tell me more about this....

Arvind Behal


This reminds me of Serratia marcescens. It's has a pinkish red pigmentation when it grows due to prodigiosin. Usually bacteria display discoloration under certain environmental condition, such as cell density in the colony. This might explain why it changes from red to cream color over time. Although, I doubt what you plated is S. marcescens as it is a bacillus instead of a cocci... ;)


Serratia marscens doesn't usually show that degree of color diversity. How fast do the colonies appear and does it ferment glucose and show bile resitance - grow on such media as MacConkey and EMB? Could you send us a picture?


I am working on it and soon will post the pics of colony as well as stained slide, and biochemicals tests will take sme time also.


here is a pic of bacteria, they are gram negative small coccus bacteria
Attached Image


Thanks - I see no change in color here and pigmentation sure looks like Serratia marcescens.

In any case, pigmentation is not an end point in identification - can you not complete that?


can you please suggest me further tests i should follow for it.


Look at "unidentified soil bacterium" discussion here in microbiology.