title: Extensive intra-phylotype diversity in lactobacilli and bifidobacteria from the honeybee gut.
abstract: BACKGROUND
  In the honeybee Apis mellifera, the bacterial gut community is consistently colonized by eight distinct phylotypes of bacteria. Managed bee colonies are of considerable economic interest and it is therefore important to elucidate the diversity and role of this microbiota in the honeybee. In this study, we have sequenced the genomes of eleven strains of lactobacilli and bifidobacteria isolated from the honey crop of the honeybee A. mellifera.
  
  
  RESULTS
  Single gene phylogenies confirmed that the isolated strains represent the diversity of lactobacilli and bifidobacteria in the gut, as previously identified by 16S rRNA gene sequencing. Core genome phylogenies of the lactobacilli and bifidobacteria further indicated extensive divergence between strains classified as the same phylotype. Phylotype-specific protein families included unique surface proteins. Within phylotypes, we found a remarkably high level of gene content diversity. Carbohydrate metabolism and transport functions contributed up to 45% of the accessory genes, with some genomes having a higher content of genes encoding phosphotransferase systems for the uptake of carbohydrates than any previously sequenced genome. These genes were often located in highly variable genomic segments that also contained genes for enzymes involved in the degradation and modification of sugar residues. Strain-specific gene clusters for the biosynthesis of exopolysaccharides were identified in two phylotypes. The dynamics of these segments contrasted with low recombination frequencies and conserved gene order structures for the core genes. Hits for CRISPR spacers were almost exclusively found within phylotypes, suggesting that the phylotypes are associated with distinct phage populations.
  
  
  CONCLUSIONS
  The honeybee gut microbiota has been described as consisting of a modest number of phylotypes; however, the genomes sequenced in the current study demonstrated a very high level of gene content diversity within all three described phylotypes of lactobacilli and bifidobacteria, particularly in terms of metabolic functions and surface structures, where many features were strain-specific. Together, these results indicate niche differentiation within phylotypes, suggesting that the honeybee gut microbiota is more complex than previously thought.
authors.affiliation: Department of Molecular Evolution, Cell and Molecular Biology, Science for Life Laboratory, Biomedical Centre, Uppsala University, Husargatan 3, SE-751 24, Uppsala, Sweden. kirsten-maren.ellegaard@icm.uu.se.
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Ellegaard
authors.affiliation: Department of Molecular Evolution, Cell and Molecular Biology, Science for Life Laboratory, Biomedical Centre, Uppsala University, Husargatan 3, SE-751 24, Uppsala, Sweden. daniel.tamarit@icm.uu.se.
authors.forename: Daniel
authors.initials: D
authors.lastname: Tamarit
authors.affiliation: Department of Molecular Evolution, Cell and Molecular Biology, Science for Life Laboratory, Biomedical Centre, Uppsala University, Husargatan 3, SE-751 24, Uppsala, Sweden. emeliejavelind@gmail.com.
authors.forename: Emelie
authors.initials: E
authors.lastname: Javelind
authors.affiliation: Department of Laboratory Medicine, Medical Microbiology, Lund University, Medicon Village, Scheelevägen 2, SE-223 62, Lund, Sweden. tobias.olofsson@med.lu.se.
authors.forename: Tobias C
authors.initials: TC
authors.lastname: Olofsson
authors.affiliation: Department of Molecular Evolution, Cell and Molecular Biology, Science for Life Laboratory, Biomedical Centre, Uppsala University, Husargatan 3, SE-751 24, Uppsala, Sweden. siv.andersson@icm.uu.se.
authors.forename: Siv G E
authors.initials: SG
authors.lastname: Andersson
authors.affiliation: Department of Laboratory Medicine, Medical Microbiology, Lund University, Medicon Village, Scheelevägen 2, SE-223 62, Lund, Sweden. alejandra.vasquez@med.lu.se.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Vásquez
mesh_terms: D000818:Animals; D001516:Bees / Q000382:microbiology*; D001644:Bifidobacterium / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D050260:Carbohydrate Metabolism / Q000235:genetics; D064112:Clustered Regularly Interspaced Short Palindromic Repeats / Q000235:genetics; D055028:Comparative Genomic Hybridization; D004269:DNA, Bacterial / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism; D014644:Genetic Variation; D016680:Genome, Bacterial; D007422:Intestines / Q000382:microbiology*; D007778:Lactobacillus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D064307:Microbiota; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S