Kitts, A. | bioRxiv Science

bioRxiv2020

Deploying and in vitro gut model to assay the impact of a mannan-oligosaccharide prebiotic, Bio-MOS(R) on the Atlantic salmon (Salmo salar) gut microbiome.

Mannose-oligosaccharide (MOS) pre-biotics are widely deployed in animal agriculture as immunomodulators as well as to enhance growth and gut health. Their mode of action is thought to be mediated through their impact on host microbial communities and associated metabolism. Bio-MOS is a commercially available pre-biotic currently used in the agri-feed industry. To assay Bio-MOS for potential use as a pre-biotic growth promotor in salmonid aquaculture, we modified an established Atlantic salmon in vitro gut model, SalmoSim, to evaluate its impact on host microbial communities. In biological triplicate, microbial communities were stabilised in SalmoSim followed by twenty-day exposure to the pre-biotic and then an eight day wash out period. Exposure the MOS resulted in a significant increase in formate (p=0.001), propionate (p=0.037) and isovalerate (p=0.024) levels, correlated with increased abundances of several principally anaerobic microbial genera (Fusobacteria, Agarivorans, Pseudoalteromonas, Myroides). 16S rDNA sequencing confirmed a significant shift in microbial community composition in response to supplementation. In conjunction with previous in vivo studies linking enhanced VFA production alongside MOS supplementation to host growth and performance, our data suggest that Bio-MOS may be of value in salmonid production. Furthermore, our data highlight the potential role of in vitro gut models to augment in vivo trials of microbiome modulators.

microbiology↗

bioRxiv2020

Development of a three-compartment in vitro simulator of the Atlantic Salmon GI tract and associated microbial communities: SalmoSim

Atlantic salmon are a species of major economic importance. Intense innovation is underway to improve salmon feeds and feed additives to enhance fish performance, welfare, and the environmental sustainability of the industry. Several gut models targeted at monogastric vertebrates are now in operation. Here we report progress in the development of an Atlantic salmon in vitro gut model, SalmoSim, to simulate three gut compartments (stomach, pyloric caecum and mid gut) and associated microbial communities. The artificial gut model was established in a series of linked bioreactors seeded with biological material derived for adult marine phase salmon. In biological triplicate, the response of the in vitro system to two distinct dietary formulations (fish meal and fish meal free) was compared to a parallel in vivo trial over forty days. 16S rDNA sequencing, qPCR, ammoniacal nitrogen and volatile fatty acid measurements were undertaken to survey microbial community dynamics and function. SalmoSim communities were indistinguishable (p=0.230) from their founding inocula at 20 days and most abundant genera (e.g. Psycrobacter, Staphylococcus, Pseudomonas) proliferated the in vitro system. Real salmon and SalmoSim responded similarly to the introduction of the novel feed, with most taxa (96% Salmon, 97% SalmoSim) unaffected, while a subset of taxa was affected non-identically across both systems. Consistent with a low impact of the novel feed on microbial community function, VFA profiles were not significantly different in SalmoSim pre and post the switch feed. This study represents an important first-step in the development of an in vitro gut system as a tool for the improvement of salmon nutrition.

microbiology↗