Ant–fungus mutualism - Wikipedia
May 9, Leafcutter ants, fungi, and bacteria The fungus, ant, bacteria relationship is so special because of the intertwined actions and benefits that. Ant–fungus mutualism is a symbiosis seen in certain ant and fungal species, in which ants actively cultivate fungus much like humans farm crops as a food source. In some species, the ants and fungi are dependent on each other for survival. The leafcutter ant is a well-known example of this symbiosis. Leaf cutter ants are sensitive enough to adapt to the fungi's reaction to different plant material, apparently.
To cultivate the fungus, the foraging ants go out and cut chunks out of leaves without ingesting any of the leave's toxic chemicals and bring them to the worker ants in the colony. Those ants take the leaves, chew them up, and use the pulp as a substrate for the fungus to grow on.
This fungus is their main food source. The fungus could not survive without the ants, and the ants cant survive without the fungus.
But the ants have a special weapon in their arsenal for cultivating the fungi. They use the antibiotic producing actinomycete bacteria, that grows on the ants, as an antibiotic against outside sources of fungi and molds. This is how they keep their nest so clean and disease free. The antibiotic agent discourages the growth of fungi, except the specific fungi that the ants are growing. This is one reason why this interaction is so interesting, the different partners work specifically with each other in order to form a balanced and well functioning system that has lasted a very long time.
Fungi Growth The leaves in the rain forest have toxic qualities in them which is supposed to deter herbivory.
But the harvesting ants cut the leaves without ingesting any of the toxins and are able to bring the leaves back to the nest. There the leaves are given to worker ants which chew up the leaves in their mouths into a paste which becomes the food source for the fungus.
The plant material is broken down through enzymes that break down the proteins and starches. Depending on the colony, the enzymes used can be slightly different promoting a complete plant break down or only a plant wall digestion. Because of the symbiotic relationship, the toxins in the leaves are able to be broken down by through enzymes from the fungi into needed sugars and proteins safe for the ant to consume.
Bacterial resistance to fungal parasites To maintain a clean and healthy fungus colony, the ants have a bacteria on their exoskeleton which they use when cultivating the fungus.
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Some ants have this on their underbelly while ants that are in constant contact with the fungus are almost completely covered with the bacteria.
This is an example of the complete evolutionary relationship bewteen the ant, the fungi, and the bacteria. The ants are able to use the bacteria, Pseudonocardia, with antibiotic qualities to fight against any invasive molds or fungi.
This bacteria is similar to the bacterium which produces half the antibiotics made today. The antibiotic qualities allow it to specifically work with the fungus to inhibit the parasitic mold. Unlike the ant, fungi, and bacteria symbiosis, present day antibiotics often produce resistant types of pathogens. It is thought that the ant colonies do not produce antibiotic resistant molds because of the high diversity of the bacteria and as the two evolve together the parasitic mold will not evolve a resistance.
Another method to cultivate only its native strain of Pseudonocardia is that the ant's feces contain incompatibility chemicals which select only for its resident fungus. There are also behavior cues which suggest that the ants physically pick out other types of fungus. Environmental Implications The millions of ants in the forests have a huge effect on the ecosystem. For such a small organism, it has a huge effect. Nitrogen Fixation Like any other garden, the ant's fungus garden needs nitrogen in an available form fit to be used by the microorganisms.
Research has showed that the fungus garden in the ants' nest fixes nitrogen. This means that the fungus is taking atmospheric nitrogen and reducing the nitrogen to produce ammonium. Even after the nest uses the nitrogen that it needs, there is still a large amount of available nitrogen that can be entered into the surrounding system.
This replenishes the nutrient poor tropical environment with an essential limiting nutrient Pinto-Tomas, Decomposition The ants cut and collect a huge amount of forest vegetation each year. Needless to say, this has a huge effect on the tropical forest system.
The decomposition effect of the ant-fungal-bacterial relationship needs to be considered when assessing the environmental impact of the relationship. When the plant material is brought to the nest, decomposition is aided by the ants chewing and initially breaking down the material, which can then be used as a substrate for the fungi. This speeds up decomposition in one place that would be spread out around the forest. Decomposition could also be hindered by the toxic qualities of the leaves leaving them inedible to other macro or micro invertebrates.
Decomposition is also aided by the previously mentioned nitrogen fixation process. Bringing nitrogen into the system helps to decrease the carbon to nitrogen ratio which speeds up the decomposition processes.
Niche This is a split side view of an underground chamber where the fungus and the queen is housed. Every new colony starts with a small room like this one,which starts with a queen moving to a new place carrying the fungus in her mouth. Nest Characteristics Nests begin when a queen ant leaves one nest with a small amount of the fungus in her mouth and moves to a different area to start her own colony.
Leafcutter ant - Wikipedia
Once a nest becomes established, the colonies can grow to have millions of ants in them. These subterranean nests vary in sizes. They can be small with a single fungus growing "room" or can be multiple feet below ground with many different rooms and complex tunnels.
Ants are also known as organized and clean insects. They have certain refuse dumps where the worker ants take the garbage and seclude it from the rest of the colony to decrease contamination.
Major Players There are a total of five major players that interact with the leafcutter ants. How is this relationship maintained when decaying leaves make such a great feast for a multitude of microbes? Ants are meticulous cleaners when it comes to caring for their crop. They remove debris and pest-infested areas in a process called weeding.
Some ants even use separate areas within the nest as a waste dump to keep debris and contaminated portions of leaves or fungus away from their prized fungus gardens.
Source While leaf-cutter ants like to maintain a tidy abode, they also populate their fungal gardens with fecal droplets. Ants also secrete phenylacetic acid and short-chain fatty acids, both with antimicrobial properties. When the ants tend to their gardens, these secreted molecules are conveniently deposited to keep their crop pest free.
The leaf-cutter ant microbiome While ants produce molecules to keep pests and invading microbes at bay, they also enlist several microbial partners to defend against pests.
Leafcutter ants, fungi, and bacteria
The most well-studied example are the actinobacteria. Worker ants conveniently carry antibiotic-producing Actinobacteria species.
Found on the underbellies of ants, the bacteria come in frequent contact with the fungus gardens.
For some ants, the bacteria completely covers their bodies, giving them the appearance as if they were covered in powdered sugar Figure 3. The association between Actinobacteria species and ants is likely due to both co-evolution and environmental acquisition from the soil.
While some ant colonies do succumb to fungal pests, many colonies thrive because invading fungi do not develop resistance to the antimicrobials produced by the bacterial mutualists.
It is possible that because the leaf-cutter ants have many mutualists, it is difficult for pests to develop resistance to several antimicrobials at once. Though how the leaf-cutter ant mutualists maintain antibiotic efficacy is still a mystery, it is clear that the mutualism is here to stay.
Over time, fungus-farming ants lost the ability to make specific nutrients and rely on the fungus for some key nutrients. The mutualism between ant and fungus is continually evolving, and examples such as these demonstrate that ants have found ways to keep this mutualism alive for thousands of years.