First insights into the effect of toxin-containing cyanobacterial extracts on the gut microbiota of teleost fishes: a microcosm study on the medaka (Oryzias latipes)

The effect of toxin-producing cyanobacterial blooms on fishes’ health has been investigated extensively, but no study to date has evaluated this effect on fish-associated microbiota. In this project, we test the effect of pure microcystins and of crude extracts of metabolites from cyanobacterial cultures on the composition of bacterial microbiota of exposed medaka fishes (Oryzias latipes). A 16S rRNA-based marker gene-based approach was used to investigate the composition of bacterial communities. Gut-associated communities differ from those occurring in the water, and among individual fish. Exposure to extracts, rather than pure microcystin, has a significant influence on gut community composition. We propose that the effect of cyanobacterial blooms on fish gut microbiota and associated functions, including toxin degradation and feed efficiency, should be further explored.