There are actually five different types of mold that have the ability to grow on bread. They are:
- penicillium
- rhizopus nigricans
- aspergillus
- mucon
- Rhizopis stolnifer.
The last is the most common.
You should never eat moldy bread. The mold has invisible 'threads' that weave through the bread, so as soon as you see visible mold, the entire loaf must go.