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28 September 2011

Farming Ants

It turns out ants, like humans, are true farmers. The difference is that ants are farming fungus.

One of the most important developments in human civilization was the practice of sustainable agriculture. But we were not the first -Just as farming helped humans become a dominant species, it has also helped leaf-cutter ants become dominant herbivores, and one of the most successful social insects in nature.

According to an article in the November issue of Microbiology Today, leaf-cutter ants have developed a system to try and keep their gardens pest-free; an impressive feat which has evaded even human agriculturalists.

Leaf-cutter ants put their freshly-cut leaves in gardens where they grow a special fungus that they eat. New material is continuously incorporated into the gardens to grow the fungus and old material is removed by the ants and placed in special refuse dumps away from the colony. The ants have also been designed to the practice of weeding. When a microbial pest is detected by worker ants, there is an immediate flurry of activity as ants begin to comb through the garden. When they find the pathogenic 'weeds', the ants pull them out and discard them into their refuse dumps.

"Since the ant gardens are maintained in soil chambers, they are routinely exposed to a number of potential pathogens that could infect and overtake a garden. In fact, many of the ant colonies do become overgrown by fungal pathogens, often killing the colony," said Professor Cameron Currie from the University of Wisconsin-Madison, USA. "Scientists have shown that a specialized microfungal pathogen attacks the gardens of the fungus-growing ants. These fungi directly attack and kill the crop fungus, and can overrun the garden in a similar fashion to the way weeds and pests can ruin human gardens."

Ants Harbor Antibiotic to Protect Their Crops

A curious observation was that some worker ants had a white wax-like substance across their bodies. When they looked at it under an electron microscope scientists discovered that this covering was not a wax, but a bacterium! These bacteria are part of the group actinobacteria, which produce over 80% of the antibiotics used by humans. The bacteria produce antifungal compounds that stop the microfungal pathogen from attacking the garden. This discovery was the first clearly demonstrated example of an animal, other than humans, that uses bacteria to produce antibiotics to deal with pathogens.

"Research in our laboratory has revealed a number of interesting properties between the bacteria and the pathogenic fungus. The bacteria appear to be specially suited to inhibiting the pathogenic fungi that infect the ants' fungus garden," said Entomologis Professor Currie of the University of Wisconsin.

"Every ant species [that we have examined] has different, highly modified structures to support different types of bacteria," Currie observes. "This indicates that the ants have rapidly adapted to maintain the bacteria. It also indicates that the coevolution between the bacteria and the ants, as well as the fungus and parasites, has been occurring since very early on, apparently for tens of millions of years."

In fact, more than 200 species of ants display this complex symbiosis, according to Currie. "It now appears that the fungus-growing ants are more modified for culturing their mutualistic bacteria than for their mutualistic fungi," Currie notes.

The unexpected finding also bears promise for human agriculture and medicine: the ants have been able to avoid promoting resistance. "I think it has to do with the ants having several mechanisms to suppress the parasite," Currie says. "In addition to the bacteria, the ants have specialized behaviors that involve removing the parasite from the fungus garden."

The Attine ants join a short list of other insects, animals and plants known to harbor beneficial microbes. Many more such species may remain to be discovered, however. "For me, it shows us how little we know about the natural systems and microbes in nature," Currie adds. "Fungus-growing ants are very well studied, yet this morphological characteristic went unnoticed until now. What other organisms might be taking advantage of this type of association? What don't we know about other systems that are not as closely studied as those of ants?"

Amazing fact: It has been estimated that an ant's brain may have the same processing power as a Macintosh computer. Another way of putting it is that a Mac has as much brains as an ant!

"There are signs for the believing nation in the creation of their (own) selves, and the creation of the animals He has scattered (across the world)." [Quran 45:4]

Courtesy: Science Daily
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