Which group of molds can be ruled out when septate hyphae are observed in a culture?

When septate hyphae are observed in a culture, Zygomycetes can be ruled out because they are characterized by coenocytic (aseptate) hyphae. Zygomycetes lack septa, which means that their hyphae do not have cross-walls dividing them into individual cells. Instead, they typically form long, multinucleate filaments. This morphological trait distinguishes Zygomycetes from other types of molds, such as Dematiaceous, Dermatophytes, and Dimorphic molds, all of which can exhibit septate hyphae.

Dematiaceous molds, for example, are a diverse group that includes various fungi with pigmented (dark) hyphae and can display septate hyphae. Similarly, Dermatophytes, which are responsible for skin infections, also exhibit septate hyphae. Dimorphic molds can switch between yeast and mold forms and likewise show septate structures in their mycelial phase. Therefore, the presence of septate hyphae effectively rules out the Zygomycetes group.