The gut microbiome and aquatic toxicology: An emerging concept for environmental health

High throughput sequencing has facilitated in depth investigations into the composition and function of host-associated microbiota in different species. Studies have revealed that the microbiome plays an essential role in the health and onset of diseases in all animals, including humans. The microbiome has emerged as a central theme in environmental toxicology, as microbes play a key, interactive role with the immune system, in addition to their role in chemical detoxification. Pathophysiological changes in the gastrointestinal tissue via perturbations by chemicals in the gut microbiota can lead to system-wide effects, resulting in poor nutrient uptake and gut inflammation. This critical review examines the literature on the effects of environmental contaminants on the microbiome of aquatic species, with a primary focus on the gut microbiome. We highlight some of the known major gut epithelium proteins in vertebrate hosts that are targets for chemical disruption, proteins that also directly cross-talk with the microbiome. These proteins are molecular targets and as such, we propose a general framework for an adverse outcome pathway that considers gut dysbiosis as a major contributing factor to adverse apical endpoints. We present two case studies that include (1) nanomaterials and (2) hydrocarbons with reference to the Deepwater Horizon oil spill to illustrate how investigations into the microbiome can improve understanding of adverse outcomes. Lastly, we suggest some strategies to functionally relate chemical-induced gut dysbiosis with adverse outcomes; these experiments are necessary in order to establish the link between specific microbes and gut dysbiosis. Further investigations into the toxicant-microbiome relationship may prove to be a major breakthrough for improving animal and human health moving forward.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 707241