title: Alternative Protein Sources in the Diet Modulate Microbiota and Functionality in the Distal Intestine of Atlantic Salmon (Salmo salar).
abstract: The present study aimed to investigate whether alternative dietary protein sources modulate the microbial communities in the distal intestine (DI) of Atlantic salmon, and whether alterations in microbiota profiles are reflected in modifications in host intestinal function and health status. A 48-day feeding trial was conducted, in which groups of fish received one of five diets: a reference diet in which fishmeal (diet FM) was the only protein source and four experimental diets with commercially relevant compositions containing alternative ingredients as partial replacements of fishmeal, i.e., poultry meal (diet PM), a mix of soybean meal and wheat gluten (diet SBMWG), a mix of soy protein concentrate and poultry meal (diet SPCPM), and guar meal and wheat gluten (diet GMWG). Samples were taken of DI digesta and mucosa for microbial profiling using high-throughput sequencing and from DI whole tissue for immunohistochemistry and expression profiling of marker genes for gut health. Regardless of diet, there were significant differences between the microbial populations in the digesta and the mucosa in the salmon DI. Microbial richness was higher in the digesta than the mucosa. The digesta-associated bacterial communities were more affected by the diet than the mucosa-associated microbiota. Interestingly, both legume-based diets (SBMWG and GMWG) presented high relative abundance of lactic acid bacteria in addition to alteration in the expression of a salmon gene related to cell proliferation (pcna). It was, however, not possible to ascertain the cause-effect relationship between changes in bacterial communities and the host's intestinal responses to the diets.IMPORTANCEThe intestine of cultivated Atlantic salmon shows symptoms of compromised function, which are most likely caused by imbalances related to the use of new feed ingredients. Intestinal microbiota profiling may become in the future a valuable endpoint measurement in order to assess fish intestinal health status and effects of diet. The present study aimed to gain information about whether alternative dietary protein sources modulate the microbial communities in the Atlantic salmon intestine and whether alterations in microbiota profiles are reflected in alterations in host intestinal function and health status. We demonstrate here that there are substantial differences between the intestinal digesta and mucosa in the presence and abundance of bacteria. The digesta-associated microbiota showed clear dependence on the diet composition, whereas mucosa-associated microbiota appeared to be less affected by diet composition. Most important, the study identified bacterial groups associated with diet-induced gut dysfunction that may be utilized as microbial markers of gut health status in fish.
authors.affiliation: Department of Basic Sciences and Aquatic Medicine, Faculty of Veterinary Medicine, Norwegian University of Life Sciences (NMBU), Oslo, Norway karina.gajardo@nmbu.no.
authors.forename: Karina
authors.initials: K
authors.lastname: Gajardo
authors.affiliation: Aquaculture and Fish Nutrition Research Group, School of Biological Sciences, Plymouth University, Plymouth, United Kingdom.
authors.forename: Alexander
authors.initials: A
authors.lastname: Jaramillo-Torres
authors.affiliation: Department of Basic Sciences and Aquatic Medicine, Faculty of Veterinary Medicine, Norwegian University of Life Sciences (NMBU), Oslo, Norway.
authors.forename: Trond M
authors.initials: TM
authors.lastname: Kortner
authors.affiliation: Aquaculture and Fish Nutrition Research Group, School of Biological Sciences, Plymouth University, Plymouth, United Kingdom.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Merrifield
authors.affiliation: BioMar, Ltd., Grangemouth, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Tinsley
authors.affiliation: Department of Basic Sciences and Aquatic Medicine, Faculty of Veterinary Medicine, Norwegian University of Life Sciences (NMBU), Oslo, Norway.
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Bakke
authors.affiliation: Department of Basic Sciences and Aquatic Medicine, Faculty of Veterinary Medicine, Norwegian University of Life Sciences (NMBU), Oslo, Norway.
authors.forename: Åshild
authors.initials: Å
authors.lastname: Krogdahl
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D017756:Aquaculture; D049109:Cell Proliferation; D031293:Cyamopsis; D004044:Dietary Proteins / Q000378:metabolism*; D000069196:Gastrointestinal Microbiome; D015870:Gene Expression; D005983:Glutens / Q000737:chemistry; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000382:microbiology*; D059013:Microbial Consortia / Q000502:physiology; D009747:Nutritional Physiological Phenomena; D011202:Poultry Products; D011506:Proteins / Q000378:metabolism; D020317:Salmo salar / Q000254:growth & development / Q000382:microbiology* / Q000502:physiology*; D013025:Glycine max / Q000737:chemistry; D014908:Triticum / Q000737:chemistry
chemical_list: D004044:Dietary Proteins; D011506:Proteins; D005983:Glutens
keywords: gut microbiota; salmon microbiota