Charissa de Bekker is an Associate Professor at the University of Utrecht specialised on environmental and molecular biology. Her research focuses on the manipulated behaviour of ants that are infected with fungal species of the genus Ophiocordyceps – the so-called ‘zombie ants’. She uses this fungus-insect interaction as a model system to study the fungal natural products involved in host manipulation and their effects on insect physiology and behavioural pathways. The overarching aim of this work is to elucidate how parasites can affect host behaviour, how behaviour is regulated and dysregulated at molecular levels, and which fungal proteins and secondary metabolites are involved.

Talk: Unraveling the hijacking strategies of zombie-making parasites: A tale of ants and fungi

Nature harbours many parasites that can induce extended behavioural phenotypes in their animal hosts. Ophiocordyceps fungi that evolved to infect and manipulate the behaviours of social insects are an evident example. The so-called “zombie behaviours” that are induced are thought to aid the fungal parasite in evading social immunity, promote fungal development, and increase transmission rates. My team’s research revolves around the elucidation of these fungal-insect interactions to learn how fungi can hijack social insect behaviour and which host pathways give rise to them. 
 
To do so, we developed the interaction of Ophiocordyceps camponoti-floridani with its carpenter ant host Camponotus floridanus as a model. In this host-microbe interaction we have observed significant changes in host daily activity rhythms, locomotion and communication, followed by summiting behaviour, which is highly characteristic for Ophiocordyceps and other manipulative infections. To investigate the interacting fungal molecules and ant host pathways that elicit these behavioural changes, we integrate omics technology with functional genetics techniques and quantitative behavioural assays.
 
With this approach, we found that Ophiocordyceps secretes a novel cysteine-rich peptide that binds to insect scramblases , thereby inducing aberrant odour-related behaviours. Moreover, we discovered that fungal indole diterpenes cause tremors in ant hosts and affect locomotion and grooming behaviours. Additionally, we found that the ant circadian clock is significantly affected during Ophiocordyceps infection. These are some of the first results to connect Ophiocordycepsgenomes with carpenter ant phenomes, thereby answering how these specialist fungi hijack ant behaviour and how those behaviours are regulated at a molecular level.