Fungus sends ants into tree to spread its spores

How a fungus turns ants into zombies

Researchers have elucidated the molecular mechanism of the fungus that turns ants into living zombies. The fungus specifically affects the ants' neurobiology, odour perception and biological clock. The Utrecht microbiologist Robin Ohm publishes this, together with American and German colleagues, in June in G3.

De schimmel groeit uit een geïnfecteerde mier, die zichzelf heeft vastgeklampt aan een tak
Fruitbody of the fungus, growing out of an infected ant that clinged itself to a tree (image: Roel Fleuren)

The fungus Ophiocordyceps camponoti-floridani can infect ants and manipulate their behaviour in a way that is beneficial for fungus growth and transmission. These infected ants are also called zombie ants. Influenced by the fungus, the ants climb to a high point and bite into a branch, attaching themselves until death.

The fungus then digests the ant, and forms a fruitbody with which the fungus spreads its spores. The molecular mechanisms behind this behavioural modification are still largely unknown –  as in similar parasitic interactions where the behaviour of a host is manipulated.

We can realistically recreate this interaction between the fungus and the ant in the lab.

"We can realistically recreate this interaction between the fungus and the ant in the lab. We have sequenced the genome of the fungus and determined all genes in it. This gives us an important tool with which we can examine this system in detail", says fungal researcher Robin Ohm. "We then looked at the expression of all genes in the fungus and the ant during the behavioural modification. In this way you get a good picture of the genes of both the fungus and the ant that may be involved in the behavioural modification."

The fungus produces toxins – such as enterotoxins, aflatrem and other toxic compounds – and all kinds of compounds associated with disrupting the foraging behaviour of the ants. "In the ants we discovered that genes involved in neurobiology, odour perception and the biological clock are affected during interaction with the fungus”, Ohm says. "These genes can explain to a large extent how the fungus adjusts the ant's behaviour. So we now have a better picture of the mechanisms behind behavioral modification in ants by fungi."

Publication

Genetic Underpinnings of Host Manipulation by Ophiocordyceps as Revealed by Comparative Transcriptomics. G3: Genes, Genomes, Genetics, June 2020. Ian Will, Biplabendu Das, Thienthanh Trinh, Andreas Brachmann, Robin A. Ohm* en Charissa de Bekker. doi.org/10.1534/g3.120.401290

*affiliated with Utrecht University