Bacteria Fight Fungus

a brown ant with pinchers stands on a leaf in the center of the photo with green trees in the background

Biological Strategy

Leafcutter ants

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Image: Filo Gèn' / Wikimedia Commons / CC BY SA - Creative Commons Attribution + ShareAlike

Protect From Fungi

Fungi–which include molds and mushrooms, amongst others–play important roles in every ecosystem, but can also create diseases in plants and animals. Fungi can rapidly reproduce, so living systems must fend them off early to avoid their spread and potential, physical harm. Living systems use both physical and chemical strategies to protect from fungi, and must ensure that these strategies don’t harm the threatened living system itself. For example, a pumpkin’s skin has antifungal proteins to prevent fungal growth without harming the pumpkin itself.

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Coevolve

Multiple living systems sometimes have such a close relationship that they end up evolving together; this is called coevolving. Coevolution occurs when changes in one living system’s genetic makeup results in changes in the other. Coevolution can result from positive, mutually-beneficial relationships. It can also result from negative relationships, such as that between a virus and its host. The host changes to avoid the virus’ harmful effects, which in turn causes a change in the virus so it can continue to predate on the host, and on through time.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Fungal gardens of leafcutter ants are free of undesired, parasitic fungus due to presence of symbiotic Streptomyces bacteria.

Where Are The Ants Carrying All Those Leaves?

Image: Jonathan Fildes /

Image: Cameron Currie / Flickr /

Streptomyces bacteria colonize the exoskeleton of leafcutter ants. The bacteria produce antifungal compounds that help the ants reduce the weed fungi that appear in their gardens.

“Cameron Currie of the Univ. of Wisconsin is studying how leafcutter ants maintain their gardens pest-free despite the presence of parasitic fungus. When worker ants were removed, the fungus overran the gardens. Currie found that a white bloom on the exoskeleton of the ants is actually a mass of Streptomyces, the same kind of bacteria that produces half of the antibiotics used in medicine. The bacteria specifically target the parasitic fungus. By studying the complex coevolution of ants, fungus, parasitic fungus, and bacteria, Currie hopes to learn about the evolution of antibiotic resistance and how mutualism and shape species diversity.” (Courtesy of the Guild)

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