A rapidly growing nonseptate mold produced colonies resembling cotton candy. What is the most likely identification?

The identification of a rapidly growing nonseptate mold with colonies resembling cotton candy aligns closely with Rhizopus species. Rhizopus spp. are known for their fast growth and characteristic appearance. They typically form dense, fluffy colonies that can appear white or grayish and have a cotton candy-like texture due to their aerial hyphae.

The term "nonseptate" indicates that the hyphae are coenocytic, which is a defining characteristic of the Zygomycetes, the division that includes Rhizopus. This trait helps in differentiating it from other molds that may have septate hyphae.

Other molds listed, such as Absidia, Penicillium, and Aspergillus, have different growth characteristics and morphological features. For example, Absidia also belongs to the Zygomycetes but may not have the same cotton candy appearance; Penicillium is typically septate and has brush-like conidiophores, while Aspergillus has distinctive conidial heads and is also septate. Thus, based on the rapid growth, nonseptate nature, and the visual description, Rhizopus spp. is the most accurate identification.