MadSci Network: Microbiology

Re: What makes bread mold turn different colors?

Date: Wed Nov 17 08:59:50 1999
Posted By: Don Schaffner, Faculty, Food Science, Rutgers University
Area of science: Microbiology
ID: 942758265.Mi

> One of my students brought in some old hamburger buns that had hot pink 
> mold on it. We had never seen pink mold. 
Actually it was probably not a mold, but a bacterium called Serratia marscencens which has a red or pinkish color. This organism is known to cause bread spoilage some times.

One way to tell if it is a bacterial or mold spoilage would be to look at it under the microscope. Mold will look like small plants, while bacteria will look like round or oblong blobs under high magnification (with a 100X lens). The structure of molds can be easily seen at lower magnification with a 20X lens.

It might also be a yeast like Rhodotorula... although I've never heard of this organism spoiling bread. Yeast also look round under the microscope, but they are bigger than bacteria.

> We are wondering if it is something in this particular kind of bread, or 
> in the environment that makes mold different colors.
The color of molds comes from their ascospores, which are the structures that these organisms use to reproduce. Ascospores are like seeds of plants, but remember molds are not plants or animals. They are part of their own kingdom called "Fungi". Mushrooms are part of this same kingdom.

Generally mold color is determined by the genetics of the organism, and not the environment. Before we had more modern genetic techniques to analyze DNA, mycologists (these are the microbiologists that study molds) classified molds according to color. Many molds still have colors in their names...

Thank you for the question...

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