WildMBI · The gut-brain axis: Interactions between the gut microbiome and host behaviour and stress in the wild

The ‘gut-brain axis’ comprises bidirectional communication pathways that mediate physiology and behaviour. Laboratory studies have shown the gut microbiome – the microorganismal community inside the gastro-intestinal tract – is part of this axis, exchanging metabolites that modify social behaviour, anxiety and stress. In turn, microbiomes can themselves be altered by host stress and social context. What remains unclear is whether, and to what extent, the gut-brain axis modulates behavioural and physiological variation under natural conditions. As a MSCA fellow, I will test the hypothesis that the gut microbiome impacts behaviour and stress physiology in free-living horses, and investigate the pathways involved. For this, I will make use of long-term data collected in the Sable Island Horse Project, Canada. This unique population study comprises repeated measurement of individual behaviour and profiling of gut (faecal) microbiome (taxonomically and functionally). Combined with de novo meta-transcriptomic data and statistical modelling, this data will allow me to assess the contribution of the gut microbiome to variation in behavioural and stress, and infer the causal links underpinning microbiome-host associations.Specifically, I will determine (1) genetic and environmental contributions to risk aversion, social position and stress, and (2) the magnitude of microbiome-host interactions. I will then (3) identify the active microbial genes and pathways that mediate stress-related traits in wild horses. My results will greatly extend our understanding of the microbiome’s function in regulating stress and behaviour under natural conditions. They may also inform future applications in welfare and conservation biology that aim to help animals cope with challenging and changing environmental conditions. This project will allow me to develop new expertise and practical skills in genomics and microbiomics while also enhancing my teaching, management and leadership skills.