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)

Abstract

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. In a 16-week seawater feeding trial, Atlantic salmon (Salmo salar) 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. 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. Lastly, 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. Overall, our data clearly indicate that responses in digesta-and mucosa-associated microbiota to dietary inclusion of insect meal differ, with the latter being more resilient to dietary changes. Microbiota | Gut biogeography | Atlantic salmon | Diet | Black soldier fly Correspondence: yanxianl@nmbu.no Characterizing intestinal microbiota and its associationsLi & Bruni et al. | bioRχiv | May 24, 2020 | 1-8 with host responses is an essential step towards identifying key microbial clades promoting fish health and welfare. Ultimately, a milestone in the fish microbiota research would be knowing how to selectively manipulate the microbiota to improve the growth performance, disease resistance and health status of farmed fish. The main aims of the work presented herein were (i) to compare distal intestinal microbiota of Atlantic salmon fed a commercially relevant diet and an insect meal-based diet, (ii) to further explore the dissimilarity between digesta-and mucosa-associated microbiota and the differences in their response to dietary changes, and (iii) to identify associations between microbial clades and host responses. This work was part of a larger study consisting of a freshwater and seawater feeding trial that aimed to investigate the nutritional value and possible health effects for Atlantic salmon of a protein-rich insect meal produced from black soldier fly (Hermetia illucens) larvae. The present work focuses on the intestinal microbiota in seawater phase Atlantic salmon fed an insect meal diet containing 15% black soldier fly larvae meal for 16 weeks. Results on feed utilization, growth performance, fillet quality, intestinal histomorphology and gene expression have been reported elsewhere (30-32). ResultsHereafter, different sample groups are named based on the combination of die...

Developmental, Dietary, and Geographical Impacts on Gut Microbiota of Red Swamp Crayfish (Procambarus clarkii)

“…However, RsaHF231 was more likely to exist during the larval or preadult stages. As a Candidatus , RsaHF231 has no cultured representatives and exist in some species, such as black soldier fly ( Hermetia illucens ), Culex mosquitoes, red swamp crayfish ( P. clarkii ) and Atlantic salmon ( Salmo salar ) [ 44 , 48 , 49 , 50 , 51 ]. There no relevant report performed RsaHF231 phylum distributed in other species.…”

“…Interestingly, RsaHF231 has been found in Atlantic salmon that was feed black soldier fly larvae meal. The reason may have partially originated from black soldier fly larvae meal [ 51 ]. For crayfish, RsaHF231 also has been found in gut microbial.…”

Black soldier fly meal effects on meagre health condition: gut morphology, gut microbiota and humoral immune response

“…Regardless of the insect's life cycle stage (larvae or prepupa), defatting process and dietary inclusion level, the use of HM was shown to increase gut microbiota diversity or richness in rainbow trout, Siberian sturgeon and Atlantic salmon (Bruni et al, 2018;Huyben et al, 2019;Józefiak et al, 2019a,b;Li et al, 2021;Rimoldi et al, 2019;Terova et al, 2019). Moreover, HM induced a shift of fish gut microbiota towards an increase of beneficial bacteria from the Firmicutes and Actinobacteria phyla, at the expense of Proteobacteria, a gram-negative phylum containing pathogens.…”

Response of gut microbiota to feed-borne bacteria depends on fish growth rate: a snapshot survey of farmed juvenileTakifugu obscurus

“…Amongst others, Pseudomonas is the most frequently reported gut-associated bacteria across many different freshwater fish species (39). On the other hand, recent studies had also raised concerns that it might represent a common contaminating bacterial taxa in molecular biology reagents (57). Whilst, considering the very rare presence of Pseudomonas in all the water and sediment samples ( Figure S7E), along with the negative amplification signal in our blank (no template) control experiment, it is highly unlikely that this bacteria taxa was introduced during libraries preparation as a contamination, rather than a biological clue reflecting the heterogeneous sample sources.…”