title: Amplicon pyrosequencing reveals spatial and temporal consistency in diazotroph assemblages of the Acropora millepora microbiome.
abstract: Diazotrophic bacteria potentially play an important functional role in supplying fixed nitrogen to the coral holobiont, but the value of such a partnership depends on the stability of the association. Here we evaluate the composition of diazotroph assemblages associated with the coral Acropora millepora throughout four seasons and at two reefs, an inshore and an offshore (mid-shelf) reef on the Great Barrier Reef, Australia. Amplicon pyrosequencing of the nifH gene revealed that diazotrophs are ubiquitous members of the bacterial community associated with A. millepora. Rhizobia (65% of the overall nifH sequences retrieved) and particularly Bradyrhizobia sp.-affiliated sequences (> 50% of rhizobia sequences) dominated diazotrophic assemblages across all coral samples from the two sites throughout the year. In contrast to this consistency in the spatial and temporal patterns of occurrence of diazotroph assemblages, the overall coral-associated bacterial community, assessed through amplicon sequencing of the general bacterial 16S ribosomal RNA gene, differed between inshore and mid-shelf reef locations. Sequences associated with the Oceanospirillales family, particularly with Endozoicomonas sp., dominated bacterial communities associated with inshore corals. Although rhizobia represented a variable and generally small fraction of the overall bacterial community associated with A. millepora, consistency in the structure of these diazotrophic assemblages suggests that they have a functional role in the coral holobiont.
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies and School of Marine and Tropical Biology, James Cook University, Townsville, Qld, 4811, Australia; Centre for Marine Microbiology and Genetics, Australian Institute of Marine Science, Townsville, Qld, 4810, Australia; AIMS@JCU, James Cook University, Townsville, Qld, 4811, Australia.
authors.forename: Kimberley A
authors.initials: KA
authors.lastname: Lema
authors.forename: Bette L
authors.initials: BL
authors.lastname: Willis
authors.forename: David G
authors.initials: DG
authors.lastname: Bourne
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000382:microbiology*; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D064307:Microbiota / Q000235:genetics; D009586:Nitrogen Fixation / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics; D020560:Proteobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D012336:RNA, Ribosomal, 16S; D010088:Oxidoreductases; C029130:nitrogenase reductase