Molds

Phylum Mucoromycota

This contains many of the bread molds (e.g., Mucor), fruit mold (Rhizopus stolonifer), as well as root endophytes and plant decomposers. This group was formerly called the Zygomycota.

Ecology and Form

- Mostly saprotrophic (feed on dead & decaying material)
- No motile cells
- Siphonous or coenocytic (long tubes without cross-walls)

Diversity

- About 1,000 species; e.g., Rhizopus

Classification

Eukaryotes

└Unikonts: fungi, slime molds, animals

└Fungi

└Zygomycota

Above: Rhizopus infecting a tomato

Above: Rhizopus infecting sweet potato

Above: mucoromycete with sporangia

Above: Dry Head Rot of sunflowers, caused by Rhizopus

Life Cycle

- Reproduce asexually, or sexually through a haplontic life cycle
- Sexual reproduction begins with gametangia on different strands (hyphae) fusing cytoplasm, mixing organelles but nuclei do not fuse (plasmogamy)
  - This is a form of conjugation.
- Nuclei fuse (=karogamy) to produce a diploid spore case (=zygo-sporangium)
- Zygosporangium goes through meiosis to produce haploid spore case (sporangia) on stalks.
- Sporangia produce haploid spores for dispersal.
- Spores germinate into new "body" (=mycelium)

Geologic Age

Ordovician - present

Questions for Thought

How are mucoromycetes similar to the chytrids?
How is the life-cycle of a mucoromycetes similar to the club or sac fungi

Additional Reading

The fungus among us: Study shows fungi form living bridges to share water between neighboring plants (Phys.org 30Jul2025)

└Bock et al. (2025) Evidence for common fungal networks among plants formed by a Dark Septate Endophyte in Sorghum bicolor

Study finds certain fungi boost the micronutrient content of bread wheat (Phys.org 23Jul2025)

└Nguyen et al. (2025) Arbuscular mycorrhizal fungal inoculation increases the bioavailability of zinc and iron in wheat grain

Plant partnership: Fungi help spruce trees fight off budworm attacks (Phys.org 23May2025)

└Ullah et al. (2025) Alliance Between Conifer Trees and Endophytic Fungi Against Insect Defoliators

Pilobolus fungi can accelerate spores at 20,000 times gravity

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