Mucoromycota

Mucoromycotina is a subphylum of uncertain placement in Fungi. It was considered part of the phylum Zygomycota, but recent phylogenetic studies have shown that it was polyphyletic and thus split into several groups, it is now thought to be a paraphyletic grouping. Mucoromycotina is currently composed of 3 orders, 61 genera, and 325 species. Some common characteristics seen throughout the species include: development of coenocytic mycelium, saprotrophic lifestyles, and filamentous.

With the treatment of Tedersoo et al. 2018, Mucoromycotina is the only subphylum under Mucoromycota. It includes a diverse group of various molds, including the common bread molds Mucor and Rhizopus. The other treatment of Mucoromycota is equivalent to current Mucoromyceta.

History

Zygomycete fungi were originally only ascribed to the phylum Zygomycota. Such classifications were based on physiological characteristics with little genetic support. A genetic study of Zygomycete fungi performed in 2016 showed that further classification of the group was possible, thus splitting it into Zoopagomycota, Entomophthoromycota, Kickxellomycotina, and Mucoromycotina. The study put these groups as being sister to Dikarya, but without further research, their exact locations in Fungi remain unknown. Many of the questions regarding these groups stem from the difficulty of collecting and growing them in culture, so the current groupings are based on the few that have been successfully collected and which could undergo genomic testing with a certain level of accuracy.

Taxonomy

The exact placement of Mucoromycotina is currently unknown. It currently resides in the subphyla incertae sedis, alongside Zoopagomycota, Entomophthoromycota, and Kickxellomycotina, whose’ placements are also currently unknown. These groups originally comprised Zygomycota alongside others that were assigned to Glomeromycota, which was elevated to phylum in 2001. These groups are sister to Dikarya, which contains Ascomycota and Basidiomycota.

Studies have currently divided Mucoromycotina into 3 orders: Endognales, Mucorales, and Mortierellales. All three orders contain species that are saprotrophic, with others forming relationships with other organisms. There are still many questions regarding Mucoromycotina and the organisms that compose it, owing to limited collected samples.

Orders

Endogonales

This order currently contains 2 families, (Endogonaceae and Densosporaceae) 7 genera, and 40 species. Not much is known about this order, other than readily noticeable characteristics. They produce subterranean sporocarps, which are ingested by small mammals attracted by the fetid odor they produce. Cultured specimens have shown that they produce coenocytic mycelium, and can be saprotrophic or mycorrhizal. This order was first described in 1931 by Jacz. & P.A.Jacz., after being monographed in 1922 by Thaxter.

Mucorales

Often referred to as pin molds, members of this order produce sporangia held up on hyphae, called sporangiophores. There are currently 13 families in this order, divided into 56 genera, and approximately 300 species. They can be parasitic or saprotrophic in nature and reproduce asexually. Much is known about this order since some of the species cause damage to stored food, with several others causing mycosis in immune compromised individuals. The order was proposed in 1878 by van Tieghem, as the examined samples did not fit in with what was Entomophthorales at the time.

Ecology

The species described in this subphylum have evolved 3 main lifestyles: saprotrophic, mycorrhizal, or parasitic. Saprotrophic species are involved in decomposition of organic matter, mycorrhizal species form symbiotic relationships with plants, and parasitic species form harmful symbiotic relationships with other organisms.

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