WP 1: Functional roles of symbiotic community of deep-sea sponges
We sequenced the 16S rRNA gene and metatranscriptomes of 18 samples representing three species of sponge in one location, and one species in 4 different locations of the Cantabrian Sea (deep-sea water). The assembled reference metatranscriptome has been uploaded to the public repository IMG/MER. Functional pathways were identified using KEGG Mapper, and core taxa and functions have been identifies for host species, and for different locations. High expression of genes related with methane metabolism, purine metabolism, benzoate degradation, and carbon fixation pathways were found among the associated bacterial members. A large percentage of transcripts were assigned to ABC transporters and Two-component systems within the membrane transport pathway, pointing to the importance of metabolite exchange between symbionts and host. Interestingly, microbial composition (16S rRNA amplicon) was congruent with the host taxonomy, and therefore followed the well-known host-specificity of the sponge microbiome, however, transcriptome sequencing revealed that two species of the same genus showed a more different symbiotic functionality than two sponges of different genera.
WP 2: Host genetic structure and environment effect on functional profiles
To disentangle the influence of the host genotype versus an environmental effect in the microbiome variation within sponge species, we sequenced the 16S rRNA gene of 393 shallow water sponges covering a range of different population structures, from weak structure (high gene flow) to high population structure. Our results showed that in sponge species with high population structure, the host genetic cluster influenced the microbial community more than the geographic location.
WP 3: Functional equivalence of microbial taxa
The taxonomic annotation of all microbial transcripts (1,2 million assembled transcripts) resulted in 537,117 different prokaryotic taxa (using UniProt database). Functional profiles of the communities of the 3 sponge species were quite similar, even though they hosted different bacterial communities, revealing that the active community perform equivalent functions. Groups of orthologous genes included 3.5% of the metatranscriptome sequences, which represented examples of functional redundancy.
WP 4: Molecular signatures for symbiosis
Eukaryotic-like protein were identified from the PFAM annotation of the translated transcripts. We identified 4,228 ELPs containing transcripts, with similar levels of expression among sponge species or locations. A total of 3,575 transcripts were identified as differentially expressed (DE) between sponge samples.
WP5: Co-ordination and management of research
Meetings were held on a regular basis in the Riesgo lab, with informal discussion occurring on an almost daily basis. Risks were managed appropriately and the project delivered efficiently. The fellow attended a variety of training sessions held for postdoctoral fellows and mixed groups at the NHM.
WP6: Outreach activities and the communication of results to a wider audience
Numerous opportunities arose to communicate work directly to the general public at events such as the European Researchers’ Night, Nature Live talks and more informally. To reach a more focused scientific community, a number of conferences and symposia were attended in the course of the project. Six papers have been published during the duration of the project, with a few more in process.
