Abstract
Background: Intestinal digesta is commonly used for studying responses of microbiota to dietary shifts, yet evidence is accumulating that it represents an incomplete view of the intestinal microbiota. The present work aims to investigate the differences between digesta- and mucosa-associated intestinal microbiota in Atlantic salmon ( Salmo salar ) and how they may respond differently to dietary perturbations. In a 16-week seawater feeding trial, Atlantic salmon were fed either a commercially-relevant reference diet or an insect meal diet containing ~15% black soldier fly ( Hermetia illucens ) larvae meal. The digesta- and mucosa-associated distal intestinal microbiota were profiled by 16S rRNA gene sequencing. Results: Regardless of diet, we observed substantial differences between digesta- and mucosa-associated intestinal microbiota. Microbial richness and diversity were much higher in the digesta than the mucosa. The insect meal diet altered the distal intestinal microbiota resulting in higher microbial richness and diversity. The diet effect, however, depended on the sample origin. Digesta-associated intestinal microbiota showed more pronounced changes than the mucosa-associated microbiota. Multivariate association analyses identified two mucosa-enriched taxa, Brevinema andersonii and unclassified Spirochaetaceae , associated with the expression of genes related to immune responses and barrier function in the distal intestine, respectively. Conclusions: Our data show that salmon intestinal digesta and mucosa harbor microbial communities with clear differences. Mucosa-associated intestinal microbiota seems more resilient to variations in the diet composition than digesta-associated intestinal microbiota. To fully unveil the response of intestinal microbiota to dietary changes, concurrent profiling of digesta- and mucosa-associated intestinal microbiota is recommended whenever feasible.
Differential response of digesta- and mucosa-associated intestinal microbiota to dietary black soldier fly (Hermetia illucens) larvae meal in seawater phase Atlantic salmon (Salmo salar)
