title: Effects of a dietary β-(1,3)(1,6)-D-glucan supplementation on intestinal microbial communities and intestinal ultrastructure of mirror carp (Cyprinus carpio L.).
abstract: OBJECTIVE
  To assess the effects of dietary Saccharomyces cerevisiae β-(1,3)(1,6)-D-glucan supplementation (MacroGard(®)) on mirror carp (Cyprinus carpio L.) intestinal microbiota and ultrastructure of the enterocyte apical brush border.
  
  
  RESULTS
  Carp were fed either a control diet or diets supplemented with 0.1, 1 or 2% w/w MacroGard(®). Culture-dependent microbiology revealed that aerobic heterotrophic bacterial levels were unaffected by dietary MacroGard(®) after 2 and 4 weeks. No effects were observed on the allochthonous lactic acid bacteria (LAB) populations at either time point; however, reduced autochthonous LAB populations were observed at week 4. PCR-DGGE confirmed these findings through a reduction in the abundance of autochthonous Lactococcus sp. and Vagococcus sp. in MacroGard(®)--fed fish compared with the control-fed fish. Overall, sequence analysis detected microbiota belonging to the phyla Proteobacteria, Firmicutes, Fusobacteria and unidentified uncultured bacteria. DGGE analyses also revealed that dietary MacroGard(®) reduced the number of observed taxonomical units (OTUs) and the species richness of the allochthonous microbiota after 2 weeks, but not after 4 weeks. In contrast, dietary MacroGard(®) reduced the number of OTUs, the species richness and diversity of the autochthonous microbiota after 2 weeks, and those parameters remained reduced after 4 weeks. Transmission electron microscopy revealed that intestinal microvilli length and density were significantly increased after 4 weeks in fish fed diets supplemented with 1% MacroGard(®).
  
  
  CONCLUSIONS
  This study indicates that dietary MacroGard(®) supplementation modulates intestinal microbial communities of mirror carp and influences the morphology of the apical brush border.
  
  
  CONCLUSIONS
  To the authors' knowledge, this is the first study to investigate the effects of β-(1,3)(1,6)-D-glucans on fish gut microbial communities, using culture-independent methods, and the ultrastructure of the apical brush border of the enterocytes in fish. This prebiotic-type effect may help to explain the mechanisms in which β-glucans provide benefits when fed to fish.
authors.affiliation: Aquatic Animal Nutrition and Health Research Group, School of Biomedical and Biological Sciences, Plymouth University, Plymouth, UK.
authors.forename: H
authors.initials: H
authors.lastname: Kühlwein
authors.forename: M J
authors.initials: MJ
authors.lastname: Emery
authors.forename: M D
authors.initials: MD
authors.lastname: Rawling
authors.forename: G M
authors.initials: GM
authors.lastname: Harper
authors.forename: D L
authors.initials: DL
authors.lastname: Merrifield
authors.forename: S J
authors.initials: SJ
authors.lastname: Davies
mesh_terms: D000821:Animal Feed; D000818:Animals; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development; D002347:Carps / Q000382:microbiology*; D058645:Denaturing Gradient Gel Electrophoresis; D019587:Dietary Supplements / Q000032:analysis; D005936:Glucans / Q000494:pharmacology*; D007422:Intestines / Q000382:microbiology* / Q000648:ultrastructure*; D064307:Microbiota / Q000187:drug effects*; D046529:Microscopy, Electron, Transmission; D008871:Microvilli / Q000648:ultrastructure; D016133:Polymerase Chain Reaction; D056692:Prebiotics
chemical_list: D005936:Glucans; D056692:Prebiotics; C033671:epiglucan
keywords: PCR-DGGE; common carp; culturable; electron microscopy; gut microbiota; immunostimulants; intestinal ultrastructure