Difference Between Mucor and Rhizopus

The main difference between Mucor and Rhizopus is that the Mucor does not have rhizoids and stolons while Rhizopus has both rhizoids and stolons. Further, Mucor has branched sporangiophore while the sporangiophore of Rhizopus is generally unbranched. Also, the Mucor does not have apophyses whereas, the Rhizopus has apophyses in the sporangia.

Mucor and Rhizopus are fungi that belong to the phylum Zygomycota. The significant feature of zygomycetes is the formation of the sporangium by the fusion of two fungal hyphae with different mating types (+ and -) as the mechanism of sexual reproduction. Hence, they are called conjugating fungi. They grow on bread and other food products.

 Key Areas Covered

1. What is Mucor
     – Definition, Characteristics
2. What is Rhizopus
     – Definition, Characteristics
3. What are the Similarities Between Mucor and Rhizopus
     – Outline of Common Features
4. What is the Difference Between Mucor and Rhizopus
     – Comparison of Key Differences

Key Terms: Hyphae, Mucor, Rhizoids, Rhizopus, Sporangia, Stolon

What is Mucor

Mucor refers to a genus of molds having round, usually cylindrical or pear-shaped sporangia not clustered and not limited in location to the points. The colonies of Mucor are fast-growing. They are white to yellow in color and become dark gray at the point of the sporangia formation. Mucor hyphae can be simple or branched. The sporangia of Mucor consist of well-developed, subtending columellae. After the dispersal of zygospores, a conspicuous collarette can be identified at the base of the columella. 

Figure 1: Mucor Sporangium

What is Rhizopus

Rhizopus refers to a genus of mold fungi including some economically valuable forms and some plant or animal pathogens. The most significant feature of Rhizopus that helps to distinguish it from Mucor is the presence of rhizoids at the base of the sporangiophore, which is called the nodal position. Rhizoids aid in the absorption of food while attaching the mycelium to the substrate as well. Also, the sporangiophore is attached to the rhizoids through a stolon. Both sporangium and the columella collapse after the dispersal of spores. 

Figure 2: Structure of Rhizopus

Similarities Between Mucor and Rhizopus

• Mucor and Rhizopus are two types of fungi that belong to the phylum Zygomycota.
• Both belong to the order Mucorales and the family Mucoraceae.
• They grow on soil, dung, vegetable matter.
• Their hyphae are broad (6-15μm in diameter), irregular, and ribbon-like.
• They form a sporangium upon the fusion of two fungal hyphae with different mating types.
• Vegetative hyphae lack septa. Hence, nuclei freely move between the cells. Septa are formed only during the formation of the sporangium.
• The cell wall of both fungal types is made up of chitosan rather than chitin.
• They undergo extracellular digestion, secreting digestive enzymes onto the substrate and absorbing nutrients.
• Both undergo asexual and sexual reproduction.
• Sporangiophores bear zygospores.
• Both form gray-white, gray-brown or brown, cottony or wooly colonies on agar rapidly without distinct margins.
• Animals may encounter them through inhalation or ingestion.
• Both are associated with sinus and pulmonary disease in individuals with a predisposition to immunosuppression, burns, diabetes, malnourishment, and intravenous drug abuse.

Difference Between Mucor and Rhizopus

Definition

Mucor: A genus of molds having round, usually cylindrical or pear-shaped sporangia not clustered and not limited in location to points

Rhizopus: A genus of mold fungi including some economically valuable forms and some plant or animal pathogens

Commonly Called

Mucor: Pin mold

Rhizopus: Black mold

Rhizoids

Mucor: No rhizoids

Rhizopus: The branch point of the sporingophor consists of rhizoids

Sporangiophore

Mucor: Branched sporangiophore

Rhizopus: Generally unbranched

Stolons

Mucor: No stolons

Rhizopus: Stolons connect sporangiophores with the rhizoids

Apophyses

Mucor: No apophyses

Rhizopus: Contain apophyses in sporangia

Sporangial Collarette

Mucor: Produces sporangial collarette on dissolving

Rhizopus: No sporangial collarette

At 40 °C

Mucor: Cannot grow

Rhizopus: Pathogenic species can grow

Pathogenicity

Mucor: Generally a contaminant

Rhizopus: Generally invasive

Colonies

Mucor: White-to-gray, cotton candy; darken with time

Rhizopus: Resemble cotton candy; darken with age into gray or yellow-brown

Conclusion

Mucor lacks rhizoids and stolons while Rhizopus has both rhizoids and stolons. Rhizoids occur at the base of the sporingophor. Stolons connect sporingophor to the rhizoids in Rhizopus. Mucor and Rhizopus produce sporangia upon the fusion of hyphae with different mating types as their sexual reproduction method. The main difference between Mucor and Rhizopus is the presence of rhizoids and stolons.

Reference:

1. McDonald, William. “Zygomycetes.” A Resident’s Fungal Morphology, Available Here

Image Courtesy:

1. “Mature sporangium of a Mucor sp. fungus” By CDC/Dr. Lucille K. Georg (Public Domain) via Commons Wikimedia
2. “Structure of Rhizopus spp.-english” (Public Domain) via Commons Wikimedia