Glomeromycota
Fungal division forming arbuscular mycorrhizas with most land plants.
Glomeromycota, commonly called glomeromycetes, are a group of fungi that includes only one class, Glomeromycetes, and about 230 known species. They were once considered one of eight fungal divisions, but current multigene phylogenetic analyses place them within the phylum Mucoromycota, making the name Glomeromycota invalid; the correct term is now subphylum Glomeromycotina. Most members form arbuscular mycorrhizas (AMs) with bryophyte thalli and the roots of vascular land plants, though not all species have been confirmed to do so. One exception, *Geosiphon pyriformis*, instead partners with *Nostoc* cyanobacteria in an endocytobiotic association. The majority of evidence indicates these fungi depend on land plants (or *Nostoc* in *Geosiphon*) for carbon and energy, though recent circumstantial evidence suggests some species might survive independently. AM-forming species are terrestrial and widespread in soils globally, associating with over 80% of plant species, and can also be found in wetlands, salt marshes, and with epiphytic plants.
Reproduction in Glomeromycota is asexual, via blastic development of hyphal tips to produce spores (glomerospores or blastospores) 80–500 μm in diameter. Some species form complex spores inside a terminal saccule. Their mycelia are generally coenocytic, occasionally with sparse septa. Recently, *Glomus* species were found to have 51 genes for meiosis, suggesting they may possess a cryptic sexual cycle.
New colonization by AM fungi depends heavily on soil inoculum. While pre-existing hyphae and infected root fragments can colonize hosts, germinating spores are key for establishing new associations. Spores are commonly dispersed by fungal and plant burrowing herbivores, with some air dispersal possible. Spore germination is triggered by specific environmental conditions—nutrient levels, temperature, or host availability—and the rate of root colonization correlates directly with spore density. Host plants also secrete chemical factors that attract and boost growth of germinating spore hyphae toward roots. Successful colonization requires a host’s fine root system, proper development of intracellular arbuscules, and a well-established external fungal mycelium. It occurs via interactions between germinating spore hyphae and root hairs, or by appressoria forming between epidermal root cells, regulated by specialized chemical si
- division
- Glomeromycota (subphylum Glomeromycotina)
- described_species
- approximately 230
- reproduction
- asexual via glomerospores (blastospores); possible cryptic sexual cycle
- symbiosis
- arbuscular mycorrhizas with land plants; Geosiphon pyriformis associates with Nostoc cyanobacteria
- habitat
- terrestrial soils worldwide, also wetlands and epiphytic plants
- orders
- 4 orders (including Paraglomerales, Archaeosporales)
Lore & Background
The Glomeromycota have generally coenocytic mycelia and reproduce asexually through blastic development of hyphal tips to produce spores (glomerospores) 80–500 μm in diameter. Recently, Glomus species were found to contain 51 genes encoding all tools necessary for meiosis, suggesting a cryptic sexual cycle. New colonization largely depends on spore density in soil; spores germinate under specific environmental conditions, and host plants secrete chemical factors that attract developing hyphae. Colonization involves interactions between germinating spore hyphae and root hairs, with intracellular hyphae forming arbuscules that facilitate two-way nutrient exchange.
Reader's Guide
Glomeromycota are ecologically significant as obligate symbionts that form arbuscular mycorrhizas with over 80% of vascular land plants, enhancing host plant responses to environmental stresses while obtaining carbohydrates from photosynthesis. Their biotrophic nature hindered laboratory study until root cultures and single-nucleus sequencing methods were developed. Molecular phylogenetics placed them within the phylum Mucoromycota, and the former phylum name Glomeromycota is now invalid, replaced by subphylum Glomeromycotina. A metatranscriptomic survey suggested that previous PCR-based studies may have underestimated their abundance due to amplification biases. Their ancient lineage and widespread distribution make them critical to understanding terrestrial ecosystem functioning and plant evolution.
Did You Know?
- One species, Geosiphon pyriformis, does not form arbuscular mycorrhizas but instead associates endocytobiotically with Nostoc cyanobacteria.
- Glomus species contain 51 genes encoding all tools necessary for meiosis, suggesting a possible cryptic sexual cycle.
- Spores of Glomeromycota can be dispersed by fungal and plant burrowing herbivore partners, and some have air dispersal capabilities.
- A metatranscriptomic survey found that 5.4% of fungal rRNA reads mapped to Glomeromycota, higher than previous PCR-based estimates.
More in Fungi And Fungus-Like Organisms 1-24
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