Bacteria fight fungus : Leafcutter Ant - AskNature
Leaf cutter ants have been fungus farming for millions of years. Reciprocal genomic evolution in the ant–fungus agricultural symbiosis. Cooperation, conflict, and coevolution in the attine ant-fungus symbiosis . Foundress queen mortality and early colony growth of the leafcutter ant, Atta texana. The leaf cutter ant, also know as the parasol ant, is one of a munber of social ant, fungus, and bacteria is one of the most amazing examples of mutualism in.
The higher attines, on the other hand, use freshly cut grass, leaves, and flowers as their fungi substrate hence the common name "leafcutter ants" and cultivate highly derived fungi. The fungus Escovopsis is a parasite in ant colonies, and the bacterium Pseudonocardia has a mutualistic relationship with ants.
Pseudonocardia resides on the ants' integuments and assists in defending the ants from Escovopsis through the production of secondary metabolites. The yeast has a negative effect on the bacteria that normally produce antibiotics to kill the parasitic fungus and so may affect the ants' health by allowing the parasite to spread.
As she leaves, she takes with her a cluster of mycelium the vegetative portion of the fungus and actually begins a new fungal garden at her resting point using this mycelium. This grows to become the new fungal farm complete with the genes of the original cultivar preserved for another generation of ants.
The relationship between attine ants and the Lepiotaceae fungus is so specialized that in many cases the Lepiotaceae is not even found outside of ant colony nests. It is clear that evolutionary pressure has been exerted on these ants to develop such an organized system in which to feed the fungus and continue its reproduction. The fungus, ant, bacteria relationship is so special because of the intertwined actions and benefits that they each have. The fungus and the ants depend on each other for survival and one can not live without the other.
The ants cultivate the fungus in its colonies from chewed up leaves and at the same time the fungus acts as the main food source for the ants.
Biological Interactions The interaction begins when a queen attine ant leaves her original nest with a chunk of the Lepiotaceae fungus in her mouth, and colonizes a new nest.
From there she can lay and the original piece of fungus can begin to be cultivated. 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.
Leafcutter ants, fungi, and bacteria - microbewiki
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.
- Leafcutter ants, fungi, and bacteria
- Leaf Cutter Ants
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.
The Leafcutter Ants: Civilization by Instinct by Bert Hölldobler
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.
The Leafcutter Ants: Civilization by Instinct
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. The sense of movement is lost.
Image by mass spectrometer to measure the amount of an antibiotic, valinomycin, on a leaf cutter ant, Acromyrmex. Leaf cutter ants, of the genera Atta and Acromyrmex, live in huge colonies and can form nests more than 30 meters in diameter. Imagine being in that nest, inside a cavern full of warm, wet fungus. Most organisms would be looking forward to gorging on this food source, or to growing there themselves.
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.
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. Scientists have found many more symbionts and garden parasites, revealing the complexity of this ecosystem.