6. The Symbiosis between the Attine Ants and the Fungi They Culture in Their Nests

Fungus-gardening (attine) ants grow fungus for food in protected gardens, which contain beneficial, auxiliary microbes, but also microbes harmful to gardens. Among these potentially pathogenic microorganisms, the most consistently isolated are fungi in the genus Escovopsis , which are thought to co-evolve with ants and their cultivar in a tripartite model. To test clade-to-clade correspondence between Escovopsis and ants in the higher attine symbiosis (including leaf-cutting and non-leaf-cutting ants), we amassed a geographically comprehensive collection of Escovopsis from Mexico to southern Brazil, and reconstructed the corresponding Escovopsis phylogeny. Contrary to previous analyses reporting phylogenetic divergence between Escovopsis from leafcutters and Trachymyrmex ants (non-leafcutter), we found no evidence for such specialization; rather, gardens from leafcutters and non-leafcutters genera can sometimes be infected by closely related strains of Escovopsis , suggesting switches at higher phylogenetic levels than previously reported within the higher attine symbiosis. Analyses identified rare Escovopsis strains that might represent biogeographically restricted endemic species. Phylogenetic patterns correspond to morphological variation of vesicle type (hyphal structures supporting spore-bearing cells), separating Escovopsis with phylogenetically derived cylindrical vesicles from ancestral Escovopsis with globose vesicles. The new phylogenetic insights provide an improved basis for future taxonomic and ecological studies of Escovopsis .

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Host Susceptibility Modulates Escovopsis Pathogenic Potential in the Fungiculture of Higher Attine Ants

Frontiers in Microbiology ◽

10.3389/fmicb.2021.673444 ◽

2021 ◽

Vol 12 ◽

Author(s):

Irina Jiménez-Gómez ◽

Mariana O. Barcoto ◽

Quimi V. Montoya ◽

Aryel C. Goes ◽

Lana S. V. E. Monteiro ◽

...

Keyword(s):

Microbial Interactions ◽

Host Susceptibility ◽

Health Impacts ◽

Disease Dynamics ◽

Agricultural Systems ◽

Pathogenic Potential ◽

The Core ◽

Attine Ants ◽

Health And Disease ◽

Basidiomycete Fungi

Health and disease emerge from intricate interactions between genotypes, phenotypes, and environmental features. The outcomes of such interactions are context-dependent, existing as a dynamic continuum ranging from benefits to damage. In host-microbial interactions, both the host and environmental conditions modulate the pathogenic potential of a microorganism. Microbial interactions are the core of the agricultural systems of ants in the subtribe Attina, which cultivate basidiomycete fungi for food. The fungiculture environment harbors a diverse microbial community, including fungi in the genus Escovopsis that has been studied as damage-causing agent. Here, we consider the ant colony as a host and investigate to what extent its health impacts the dynamics and outcomes of host-Escovopsis interactions. We found that different ant fungal cultivars vary in susceptibility to the same Escovopsis strains in plate-assays interactions. In subcolony-Escovopsis interactions, while healthy subcolonies gradually recover from infection with different concentrations of Escovopsis conidia, insecticide-treated subcolonies evidenced traits of infection and died within 7 days. The opportunistic nature of Escovopsis infections indicates that diseases in attine fungiculture are a consequence of host susceptibility, rather than the effect of a single microbial agent. By addressing the host susceptibility as a major modulator of Escovopsis pathogenesis, our findings expand the understanding of disease dynamics within attine colonies.

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Condensed tannins, attine ants, and the performance of a symbiotic fungus

Journal of Chemical Ecology ◽

10.1007/bf01402942 ◽

1991 ◽

Vol 17 (6) ◽

pp. 1177-1195 ◽

Cited By ~ 17

Author(s):

Colin Nichols-orians

Keyword(s):

Condensed Tannins ◽

Symbiotic Fungus ◽

Attine Ants

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Phylogenetic analysis of mutualistic filamentous bacteria associated with fungus-growing ants

Canadian Journal of Microbiology ◽

10.1139/w05-023 ◽

2005 ◽

Vol 51 (6) ◽

pp. 441-446 ◽

Cited By ~ 89

Author(s):

Matías J Cafaro ◽

Cameron R Currie

Keyword(s):

Phylogenetic Analysis ◽

Morphological Type ◽

Phylogenetic Position ◽

Bacterial Cells ◽

Filamentous Bacteria ◽

Attine Ants ◽

Dense Membrane ◽

Transmission Electron ◽

The Family ◽

Fungus Growing Ants

The attine ant–microbe system is a quadripartite symbiosis, involving a complex set of mutualistic and parasitic associations. The symbiosis includes the fungus-growing ants (tribe Attini), the basidiomycetous fungi the ants cultivate for food, specialized microfungal parasites (in the genus Escovopsis) of the cultivar, and ant-associated mu tualistic filamentous bacteria that secrete antibiotics specifically targeted to suppress the growth of Escovopsis. In this study, we conduct the first phylogenetic analysis of the filamentous mutualistic bacteria (actinomycetes) associated with fungus-growing ants. The filamentous bacteria present on 3 genera of fungus-growing ants (Acromyrmex, Trachy myrmex, and Apterostigma) were isolated from 126 colonies. The isolated actinomycetes were grouped into 3 distinct morphological types. Each morphological type was specific to the ant genus from which it was isolated, suggesting some degree of host specificity. The phylogenetic position of the 3 morphotypes was estimated using 16S rDNA for representative strains. The 8 isolates of actinomycetes sequenced are in the family Pseudonocardiaceae (Actino mycetales) and belong to the genus Pseudonocardia. Transmission electron microscopy examination of the actino mycete associated with the cuticle of Acromyrmex sp. revealed bacterial cells with an outer electron-dense membrane, consistent with actinomycetes in the genus Pseudonocardia. Ant-associated Pseudonocardia isolates did not form a monophyletic group, suggesting multiple acquisitions of actinomycetes by fungus-growing ants over their evolutionary history.Key words: actinomycetes, Pseudonocardia, phylogeny, mutualism, attine ants.

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