Ant–fungus mutualism - Wikipedia
However, the true relationship between fungi and animals are often not known. . the mound-building termites of Africa and Asia, and the leaf-cutting ants of cassava and citrus fruits failed because of their inability to control these ants. Trying to capture the movement of a colony of leaf-cutter ants in a single photo So it seemed that this was a 3 way mutualism: the ant, the fungus it feeds on, Fungus-growing ants use antibiotic-producing bacteria to control. Many organisms participate in symbiotic relationships with other organisms, Leaf-cutting ants maintain an obligate symbiosis with their fungal cultivar Similarly, control over which endophytes can remain in the garden may.
The ants meticulously clean their fungus gardens and even secrete an antimicrobial acid to keep themselves from bringing in outside visitors, but is that enough to fend off the various microbial and fungal intruders?
He found this same microbe living not just on one, but many leaf-cutter ant species, including two genera of fungus-growing ants that evolved earlier than the leaf-cutters Atta and Acromyrmex we know and love.Cordyceps: attack of the killer fungi - Planet Earth Attenborough BBC wildlife
So it seemed that this was a 3 way mutualism: Is anything in biology ever so simple? The hunt began to find more bacterial antibiotic-producing symbionts.
Mutualism and Leaf Cutter Ants: How It All Works
Scientists have found many more symbionts and garden parasites, revealing the complexity of this ecosystem. Additionally, if there are many species of microbes around, an evolutionary arms race can emerge in which the microbes try to outcompete one another, creating stronger and stronger antibiotics which could be harmful.
Instead of simply listing off the species of microbes they discover on ants, Dieter Spiteller and his lab have been working to identify the antibiotics they produce.
This approach allows them to more easily identify what antibiotic types work on what pathogens and parasites and see what combinations of antibiotics show up together.
Many of these microbial symbionts are not well-studied, if at all, so figuring out what type of antibiotic they are producing is a bit of a trick. This allowed them to narrow down their screen to look for the antibiotics that were most likely being produced by each bacterial species instead of having to screen for ALL of them.
Ant fungiculture is thought to have evolved from a state where ants took advantage of the metabolic activities of fungi to digest plant polysaccharides and other plant compounds that are difficult to digest Mueller et al. Like most fungi, the cultivated fungus secretes exo-enzymes, and the ants imbibe these enzymes when feeding on the fungus.
Seal and Tschinkel b. An important feature of fungi is that hyphal secretions can contain somatic incompatibility compounds that stimulate rejection reactions in fungi of different genotypes Worralwhere the incompatibility response is positively correlated with genetic distance between the interacting fungal strains Hansen et al.
According to the FCM, the ants perceive somatic incompatibility among genetically different strains and react accordingly by killing and removing foreign, incompatible cultivars Bot et al. The intensity of their behaviors is correlated with genetic distances between interacting fungi, so that the more distantly related a foreign cultivar is, the greater is the likelihood of rejection by the ants Poulsen and Boomsma Such rejection mediated via ant recognition mechanisms is thought to occur much more rapidly than rejections mediated solely via mycelial contact minutes or hours vs.
Apart from the studies discussed above, no additional studies have addressed the FCM in greater detail. It is unknown whether the ants have a choice in determining the genotype of fungus they are cultivating.
The FCM predicts that, after adopting a foreign fungus for sufficient time i.
Chemical warfare between leafcutter ant symbionts and a co-evolved pathogen
Several current studies seem to contradict general applicability of the FCM by demonstrating that attine colonies can readily adopt novel cultivars without rejection Seal and Tschinkel a; Sen et al. It is thus unclear whether monocultures are in fact maintained by the fungus or by the ants using other cues to maintain their monocultures. Experimental symbiont switches between the fungus-gardening ant Trachymyrmex septentrionalis and a cultivar symbiont from the leaf-cutting ant Atta texana occurred without overt rejection behavior; nor did the switches incur any clear costs in performance fitness Seal and Tschinkel a.
The latter was surprising because the corresponding genetic distances between the fungal species of A. We examine here several predictions of the FCM by repeating the cultivar-switch experiment on T. We found that, if switched colonies were successful at retaining even a miniscule piece of their old garden, the ants in a colony will form a chimeric garden over the course of a month, and this chimeric garden will revert within 1—2 weeks back to the original species.
These observations suggest that the workers in a colony have an innate preference for their native fungal species. Workers therefore retain their original fungal preference even when experimentally switched to a foreign fungus, which contradicts the FCM.
Furthermore, behavioral preferences seem to operate independently of hypothesized fungal incompatibility compounds. Thus, the monocultures in this symbiosis seem to be reinforced by factors intrinsic to both the ants and the fungi.
This species is among the most abundant and conspicuous ants in pine forests throughout the southeastern United States Seal and Tschinkel ; Seal and Tschinkel, Data Availability Statement The authors declare that the data supporting the findings reported in this study are available within the article and the Supplementary Information, or are available from the authors on reasonable request.
Nucleotide sequences and annotations of the BGCs identified in E.
Abstract Acromyrmex leafcutter ants form a mutually beneficial symbiosis with the fungus Leucoagaricus gongylophorus and with Pseudonocardia bacteria.
Both are vertically transmitted and actively maintained by the ants. The fungus garden is manured with freshly cut leaves and provides the sole food for the ant larvae, while Pseudonocardia cultures are reared on the ant-cuticle and make antifungal metabolites to help protect the cultivar against disease.
If left unchecked, specialized parasitic Escovopsis fungi can overrun the fungus garden and lead to colony collapse. We report that Escovopsis upregulates the production of two specialized metabolites when it infects the cultivar.