Epiphytic Planctomycetes communities associated with three main groups of macroalgae

Planctomycetes, a unique group of widespread and understudied bacteria, are known to be associated with macroalgae. The temporal dynamics and the host-specific association of planctomycetal communities on Fucus spiralis, Ulva sp. and Chondrus crispus from two locations in the North Coast of Portugal were assessed both by denaturing gradient gel electrophoresis with group-specific primers and 16S rDNA amplicon libraries. The epiphytic planctomycetal communities showed a significant association with the host macroalgal species independently of the geographical location and the season. This pattern was confirmed by clone libraries of winter and summer samples: we obtained 720 16S rRNA gene sequences that represented 44 operational taxonomic units (OTUs) within the phylum Planctomycetes. Most of the OTUs belonged to Blastopirellula, followed by Rhodopirellula, Planctomyces, the Pir4 lineage and the uncultured class OM190 (this last one nearly 30% of the OTUs). Ulva sp. and C. crispus had more diverse planctomycetal communities than F. spiralis. Analysis of beta diversity showed that the planctomycetal microbiome was host specific. We hypothesize that the specific association of Planctomycetes and their macroalgal hosts is likely determined by nutritional molecules provided by the algae and the set of sulfatases inherent to each Planctomycetes species. © FEMS 2017.

This work was partially supported by the Strategic Funding UID/Multi/04423/2013 through national funds provided by FCT – Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programme PT2020. The first author was financed by FCT [PhD grant SFRH/BD/35933/2007] and by a Marie Curie short term fellowship Ph.D. stipend in MarMic EST at Max Planck Institute for Marine Microbiology, Bremen. The work was also partially supported by a US NIH National Institute of General Medical Sciences INBRE award grant P20 GM103475 attributed to F. G-V.