Over the past 20 years, research into the microbiome has exploded. Increasingly, experimental and clinical evidence suggests that the gut microbiota is linked to many host physiological processes, particularly immunology, metabolism, and gut physiology.

There is strong evidence for interactions between the gut microbiota and infections with a range of eukaryotic parasites. The composition of the gut microbiota is altered during many parasite infections and specific parasite-bacterial interactions can facilitate or impede infection. The parasitic trematode, Fasciola hepatica, is a major parasite of domestic livestock but we know very little about how F. hepatica interacts with host microbiomes.

We investigated how a major parasitic trematode of domestic livestock, Fasciola hepatica, could impact the gut microbiota of sheep throughout time. Sheep from a single, co-housed group were split into multiple, replicate pens, each containing both infected and control sheep. Unexpectedly, we found that faecal microbiomes were more determined by pen than by infection. As the microbiomes changed over time, they differed more between pens than between infected and control sheep. Inferred metagenomic analysis from 16S rRNA data predicted metabolic differences between the microbiome’s characteristic of the different pens, indicating that microbiome drift could have functional consequences for the host.

The microbiome is an increasingly active field in health-related research, and so presenting our findings to the infection and immunity group at the ECR symposium was a great opportunity. We highlighted how microbiome drift in isolated groups of animals resulted in increasing differences between the groups and could result in animals which responded differently to metabolic challenges. The consequences of microbiome drift in experimental settings have not yet been widely addressed as possible confounders, but such a fundamental concept could explain the large variability in outcomes we see in longitudinal studies. Overall, the concept of microbiome drift was very well received, winning the best oral presentation award, but, more importantly, it spurred discussions about how we should approach microbiome experiments using isolated populations in the veterinary and human medical spheres.

Abbie Williams, SWBio DTP student

Overview of the University of Bristol’s Infection and Immunity Research Network ECR symposium.