Mucormycetes (formerly known as the Zygomycetes) grow extremely rapid both in vivo and in culture. They are often called "lid lifters" because of their fluffy and voluminous aerial mycelia that can lift the lid off of plates whose lids aren't taped on. Their hyphae are broad and have few septae, making them floppy and ribbonlike. Their branching is infrequent, haphazard and nondichotomoous. Extreme care must be taken not to grind specimens prior to culture if zygomycosis is a consideration as the grinding process can disrupt all of the viable hyphae. Instead, tissue specimens should be minced.
Distinct morphological features permit identification of Mucormycetes, and distinguish them from hyaline and dematiaceous molds. Of note, it is important to document the presence or absence of rootlike structures called rhizoids, and their location, and to determine whether the sporangiosphores are branched or unbranched (simple).
The image to the right shows a lactophenol cotton blue preparation of a Mucor species.
Image courtesy of the CDC.
