MadSci Network: Microbiology

Re: How do Rhizopus Stolonifer, Pencillum, and Aspergillus differ/same?

Date: Sun Feb 21 22:29:43 2010
Posted By: Billy Carver, Grad student, Biomedical Sciences, Vanderbilt University
Area of science: Microbiology
ID: 1266774442.Mi

Hey Kayla –

This is a really interesting question. I am personally very interested in fungi so I’ll tell you what I know. As you’ve mentioned all of these fungi are pretty common on bread. Rhizopus colonies tend to be grayish brown and sort of fuzzy. Penicillium colonies are almost always teal with a white outline. Aspergillus colonies can range from brown to black and are usually fuzzy, like Rhizopus. All three of these genera contain several species – you mentioned, for instance, Rhizopus stolonifer. This is certainly a common species of Rhizopus, but not the only one that grows on bread.

Fungi as a kingdom are separated into roughly four major phyla based on how they sexually reproduce.

The genera Aspergillus and Penicillium belong to Actinomycota. Rhizopus is a Zygomycete.

Now, I’ve already mentioned what these three genera look like as colonies. On a microscopic level Penicillium is definitely the most striking; it sort of looks like long, elaborate fans made of cells. They branch off like coral almost, and are sort of a pale green color under the microscope. Aspergillus gets its name from the tool that Catholic priests use to sprinkle holy water, called an aspergillum. They have long stalks with a fuzzy ball at the end. The fuzzy ball is where the spores are. Finally, under the microscope Rhizopus species just look like tangles of hyphae (fungal cells) with big balls interspersed between them (these are the zygospores). I suggest you use a search engine to find some of the great pictures of these fungi on the internet – there are good ones out there.

As far as what they eat, fungi aren’t especially finicky eaters. All fungi release enzymes into their surroundings that digest large macromolecules (like the starch in bread, for instance) and then absorb the smaller molecules to use for energy. Starch can be easily converted into glucose by these enzymes, and glucose is a great source of carbon and energy. The most important factor for fungi to grow is moisture – they require a lot of moisture. That’s why you don’t often see fungus on dried bread crumbs.

I hope this has helped you out. I do enjoy talking about fungi… I guess you could say I am one fun guy.


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