A specific mix of generalists: bacterial symbionts in Mediterranean Ircinia spp

• Published in: FEMS microbiology ecology 2012-03, Vol.79 (3), p.619-637
• Main Authors: Erwin, Patrick M., López-Legentil, Susanna, González-Pech, Raúl, Turon, Xavier
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Animals; Bacteria; Bacteria - classification; Bacteria - genetics; Bacteria - growth & development; bacterial symbionts; Bacteriology; Base Sequence; Biodiversity; Biological and medical sciences; COI; Community structure; Ecology; Fundamental and applied biological sciences. Psychology; Genes, rRNA; Genetic Variation; host specificity; Ircinia; Ircinia fasciculata; Ircinia oros; Ircinia variabilis; ITS‐2; Marine; Mediterranean Sea; Microbial ecology; Microbiology; Microorganisms; Miscellaneous; Molecular Sequence Data; phylogenetics; Phylogeny; Porifera - classification; Porifera - genetics; Porifera - microbiology; Porifera - ultrastructure; RNA, Ribosomal, 16S - genetics; sponge; Symbiosis; Various environments (extraatmospheric space, air, water)
• ISSN: 0168-6496; 1574-6941
• DOI: 10.1111/j.1574-6941.2011.01243.x

Abstract Microbial symbionts form abundant and diverse components of marine sponge holobionts, yet the ecological and evolutionary factors that dictate their community structure are unresolved. Here, we characterized the bacterial symbiont communities of three sympatric host species in the genus Ircinia from the NW Mediterranean Sea, using electron microscopy and replicated 16S rRNA gene sequence clone libraries. All Ircinia host species harbored abundant and phylogenetically diverse symbiont consortia, comprised primarily of sequences related to other sponge-derived microorganisms. Community-level analyses of bacterial symbionts revealed host species-specific genetic differentiation and structuring of Ircinia-associated microbiota. Phylogenetic analyses of host sponges showed a close evolutionary relationship between Ircinia fasciculata and Ircinia variabilis, the two host species exhibiting more similar symbiont communities. In addition, several bacterial operational taxonomic units were shared between I. variabilis and Ircinia oros, the two host species inhabiting semi-sciophilous communities in more cryptic benthic habitats, and absent in I. fasciculata, which occurs in exposed, high-irradiance habitats. The generalist nature of individual symbionts and host-specific structure of entire communities suggest that: (1) a ‘specific mix of generalists’ framework applies to bacterial symbionts in Ircinia hosts and (2) factors specific to each host species contribute to the distinct symbiont mix observed in Ircinia hosts.