Vibrio species are predominantly intracellular within cultures of Neoparamoeba perurans, causative agent of Amoebic Gill Disease (AGD)

Neoparamoeba perurans is a free-living protist that can cause Amoebic Gill Disease (AGD) in a number of teleost fish species and is responsible for substantial losses of farmed Atlantic salmon in various locations world-wide. The intimate relationship of the amoeba with bacteria can present challenges for its laboratory culture and drug discovery programmes. Herein, we report our findings on the bacteria that live in close association with N. perurans. These include the presence of various marine bacteria, including those of the Pseudoalteromonas, Halomonas, Cellulophaga and Mesonia genera. However, next generation sequencing (NGS) identified a substantial proportion of sequences that matched with the Vibrio genus in filtered amoebae and not in the medium suggesting an intimate association between this genus and N. perurans. Fluorescence in-situ hybridization (FISH) revealed that Vibrio species are predominantly found within N. perurans. This information is important in the management and control of AGD as bacteria associated with N. perurans may have relevance to virulence and advancement of disease.