Mucor heterogamus, previously known as Zygorhynchus heterogamus, is a zygomycete fungus. According to MycoBank, the current name is Zygorhynchus heterogamus. According to MycoCosm, however, the current name is Mucor heterogamus. This species page will refer to the fungus as Mucor heterogamus. This is because genetic analysis has shown that the genus Zygorhynchus is not distinct from the genus Mucor (Anonymous). Mucor heterogamus was first described by Jean Paul Vuillemin in the Bulletin de la Société Mycologique de France in 1887. Its epithet is heterogamus. In a 2013 analysis of Mucor heterogamus, authors found that morphologically living cultures of the fungus were almost identical to Villemin's first descriptions. The main difference was zygospore projection length. The authors note, however, on a molecular level there is variability in the ITS region of this fungus. Because of this variability they suggest further multi locus DNA analysis is needed to clarify possible speciation (Walther G, 2013).
Mucor heterogamus has a spherical multispored sporangia. The sporangial wall, which becomes liquefied, shows a columella. The ornamented zygospores are formed between differently sized suspensors (Anonymous). The most distinctive feature of Mucor heterogamus are the black and blunt zygospores. A full description of the morphology has been provided in Domcsch’s Compendium of Soil Fungi. It reads: “sporangiophores arising from the substrate mycelium, erect, to 18 µm wide, ± sympodially branched. Sporangia almost hyaline, globose, 15-35 (-55) µm diameter, on erect or nodding sporangiophore tips, the wall breaking of deliquescing at maturity; columella applanate to subglobose, 6·5-26µm diameter (Domsch, 1980).” Macroscopic descriptions of Mucor heterogamus on a synthetic Mucor agar show grey to olive gray colonies that average low growth height when incubated at 20-25 degrees Celsius. Said colonies cover a 9 cm Petri dish in approximately 10 days (Domsch, 1980).
The sporangia of species ofZygorhynchusare globose, nonapophysate, and with a deliquescent wall. Zygospores form zygosporangia that have a brown to black, roughened wall. The suspensors are opposed and heterogamous (at maturity, one suspensor is as large, or nearly so, as the zygosporangium, and the other usually is barely, or not, visible). All known species are homothallic.
Seven taxa ofZygorhynchusare recognized by Hesseltine et al. (1959). An eighth species was added by Zheng (2002). Schipper 1986) retains species ofMucortransferred toZygorhynchusby von Arx (1982) inMucor. Schipper et al. (1975) and O’Donnell et al. (1978) presentSEMpictures of zygosporangial ornamentation. Edelmann and Klomparens (1995) studied the ontogeny of zygospore formation and suggested the standardization of structural names.Zygorhynchusis a common member of the mucoralean flora of some soils.(Zygomycetes 2015)
Research shows few localities for this given fungus. However, in a study done in 2015, in which the fungal diversity was assessed in a periglacial area of the Italian Alps, Mucor heterogamous was dedicated. The site was chosen to observe the change in microbial communities impacted by environmental changes due to climate effects. Mucor heterogamous was found at 2 sites, at 2290 meters above sea level and at 2750 meters above sea level (Marinella Rodolfi, 2015).
The specific ecological roles of Mucor heterogamus are not specified thus far. To provide some ecological context for this fungus, information on a related species, Mucor indicus, is provided. Mucor indicus, like Mucor heterogamus, is a member of the family Mucoracea. Mucor indicus is able to ferment pentoses and hexoses for the production of ethanol (Anonymous).
More generally still, members of the order Mucorales, to which both Mucor indicus and Mucor heterogamus belong, are soil inhabitants. However members of this order may inhabit mammalian hosts, as these organisms are thermotolerant. Within these hosts, the pathogenicity is considered to be strain specific (Anonymous). Iron seems to be related to survivability of fungi in this order (Shipton, 2012).
Mucor heterogamus is part of a project called the 1000 Fungal Genomes Project that aims to provide scientific reference material. The project is a collaboration between the Joint Genome Institute of the Department of Energy and a team of scientists, including Joseph Spatafora at Oregon State University. This project is documented online at MycoCosm, the fungal genome resource. According to MycoCosm, the whole genome sequencing of this fungus provides information to the evolution of mating type locus (Anonymous).
Mucor heterogamous is ecologically significant. The fungus has been used in herbicide toxicity studies. In one such examination on the toxicity of the herbicides paraquat and diquat on four soil fungi, Mucor heterogamous was unable to degrade either compound. To understand the significance of this study, it is important to point out that these herbicides are commonly used in the environment. Diquat is a non selective herbicide used for the control of unwanted plants in wetland and agricultural areas (Resources). Environmental interactions are addressed in the commercialization of an herbicide for multiple reasons. First, it is of interest whether the herbicide persists in the soil for human and environmental safety. Second it is important whether the herbicide is degraded by microbial activity prior to application and control of targeted plant material. As such a study on the microbial interaction of this herbicide was conducted. Again, Mucor heterogamous was unable to degrade either diquat or paraquat. A tolerance to these herbicides was measured by the ability of the fungi to degrade the compounds. Fungi without tolerance showed high intracellular levels of the herbicide (Smith, 1976). In another study reported by the Bureau of Land Management for the Ecological Risk Assessment of diquat, that supported the previous findings, Mucor heterogamus was unable to degrade diquat in the soil. The herbicide, at 3 µg/g persisted in the soil for 9 months (Anonymous, 2005).
Mucor heterogamus belongs to the kingdom Fungi, phylum Mucoromycota, subphylum Mucoromycotina, order Mucorales, family Mucoraceae and genus Mucor (Anonymous, 2016). This fungus has been included in molecular phylogenetic studies. A phylogenetic analysis of the nuclear ribosomal internal transcribed spacer region (ITS rDNA) and partial nuclear ribosomal large subunit (LSU rDNA) showed that his fungus is polyphyletic and not distinct from Mucor. MycoCosm, the fungal genomics resource, published this information as the reason why the genus Zygorhynchus has been removed and reclassified as the Mucor genus. Originally the genus Zygorhynchus was used to differentiate the fungus from others in the Mucor group based on the following qualities: spherical multispored sporangia, sporangial wall that becomes liquid at maturity and brown or blackish ornamented zygospores formed between differently sized suspensors (Anonymous). In 1980 Lendner recognized fifty one species of fungi in the genus Mucor, including Mucor heterogamus in addition to Glomerula repent, Parasitella simplex and others (Povah, 1917). Mucor heterogamus is most closely related to eight other homothallic species within Mucor found in diverse soils (Domsch, 1980).
