Genomics and phylogeny of the proposed phylum 'Candidatus Poribacteria' associated with the excavating sponge Thoosa mismalolli

Changes in microbiome composition during ontogeny and dispersal of the coral boring sponge Thoosa mismalolli

Dispersal is an important life history trait that plays a key role in the demography and evolution of species. We employed a combined approach of DNA sequencing and transmission electron microscopy to examine the changes in the microbiome during the ontogeny and dispersal of the coral-excavating sponge Thoosa mismalolli. The results show that sponge can acquired their associated bacteria via both vertical (VT) and horizontal transmission (HT). Adult sponges, brooding larvae, and early free-swimming sponge larvae harbor a similar high-diversity microbial assemblage, dominated by Proteobacteria and Chloroflexi, which change throughout the larval dispersal phase. Larvae collected offshore showed a reorganization of their microbiome with a significant reduction of the dominance of inherited bacteria (Proteobacteria and Chloroflexi), and an enrichment of environmentally derived bacteria taxa (Bacteroidetes, Tenericutes, and Firmicutes). TEM confirmed a substantial change in cell structure and microbial composition, attributed to symbionts' massive phagocytosis. This research provides information on microbiome dynamics through the sponge ontogeny and sheds on their possible role in the dispersal capacity of their larvae.

Phylogenomic analysis of the Ponticus clade: strains isolated from the spotted rose snapper (Lutjanus guttatus)

The family Vibrionaceae is classified into many clades based on their phylogenetic relationships. The Ponticus clade is one of its clades and consists of four species, Vibrio panuliri, V. ponticus, V. rhodolitus, and V. taketomensis. Two strains, CAIM 703 and CAIM 1902, were isolated from the diseased spotted rose snapper external lesion (Lutjanus guttatus), they were analyzed to determine their taxonomic position, a phylogenetic analysis was performed based on the 16S rRNA sequences proved that the two strains are members of the genus Vibrio and they belong to the Ponticus clade. Then, a phylogenomic analysis was performed with four type strains and four reference strains isolated from marine organisms and aquatic environments. Multilocus Sequence Analysis (MLSA) of 139 single-copy genes showed that CAIM 703 and CAIM 1902 belong to V. panuliri. The 16S rRNA sequence similarity value between CAIM 703 and CAIM 1902 was 99.61%. The Ponticus clade species showed Average Nucleotide Identity (ANI) values between 78 to 80% against the two strains for ANIb, except V. panuliri LBS2T (99% and 100% similarity). Finally, this analysis represents the first phylogenomic analysis of the Ponticus clade where V. panuliri strains are reported from Mexico.

A Study of Sponge Symbionts from Different Light Habitats

The amount of available light plays a key role in the growth and development of microbial communities. In the present study, we tested to what extent sponge-associated prokaryotic communities differed between specimens of the sponge species Cinachyrella kuekenthali and Xestospongia muta collected in dimly lit (caves and at greater depths) versus illuminated (shallow water) habitats. In addition to this, we also collected samples of water, sediment, and another species of Cinachyrella, C. alloclada. Overall, the biotope (sponge host species, sediment, and seawater) proved the major driver of variation in prokaryotic community composition. The light habitat, however, also proved a predictor of compositional variation in prokaryotic communities of both C. kuekenthali and X. muta. We used an exploratory technique based on machine learning to identify features (classes, orders, and OTUs), which distinguished X. muta specimens sampled in dimly lit versus illuminated habitat. We found that the classes Alphaproteobacteria and Rhodothermia and orders Puniceispirillales, Rhodospirillales, Rhodobacterales, and Thalassobaculales were associated with specimens from illuminated, i.e., shallow water habitat, while the classes Dehalococcoidia, Spirochaetia, Entotheonellia, Nitrospiria, Schekmanbacteria, and Poribacteria, and orders Sneathiellales and Actinomarinales were associated with specimens sampled from dimly lit habitat. There was, however, considerable variation within the different light habitats highlighting the importance of other factors in structuring sponge-associated bacterial communities.