Sponges-Cyanobacteria associations: Global diversity overview and new data from the Eastern Mediterranean

Abstract

Sponge-cyanobacteria associations have attracted research interest from an ecological, evolutionary and biotechnological perspective. Current knowledge is, in its majority, “hidden” in metagenomics research studying the entire microbial communities of sponges, while knowledge on these associations is totally missing for certain geographic areas. In this study, we (a) investigated the occurrence of cyanobacteria in 18 sponge species, several of which are studied for the first time for their cyanobionts, from a previously unexplored eastern Mediterranean ecoregion, the Aegean Sea, (b) isolated sponge-associated cyanobacteria, and characterized them based on a polyphasic (morphological-morphometric and molecular phylogenetic analysis) approach, and (c) conducted a meta-analysis on the global diversity of sponge species hosting cyanobacteria, as well as the diversity of cyanobacterial symbionts. Our research provided new records for nine sponge species, previously unknown for this association, while the isolated cyanobacteria were found to form novel clades within Synechococcus, Leptolyngbyaceae, Pseudanabaenaceae, and Schizotrichaceae, whose taxonomic status requires further investigation; this is the first report of a Schizotrichaceae cyanobacterium associated with sponges. The extensive evaluation of the literature along with the new data from the Aegean Sea raised the number of sponge species known for hosting cyanobacteria to 320 and showed that the cyanobacterial diversity reported from sponges is yet underestimated.

Leptothoe, a new genus of marine cyanobacteria (Synechococcales) and three new species associated with sponges from the Aegean Sea

“…Leptolyngbya ‐like cyanobacteria are, in comparison to other filamentous cyanobacteria, the most frequently found in association with sponges (Konstantinou et al. ). Our results show that the three new sponge‐associated Leptothoe species were hosted by four different sponge species, suggesting a degree of host specificity.…”

“…The four cyanobacteria strains investigated in this study were previously isolated from sponges and identified as members of the genus Leptolyngbya (Konstantinou et al. ) while one more strain was isolated from sponges during the present study following the same methods (Table in the Supporting Information). These strains are maintained in the Microalgae and Cyanobacteria Collection (TAU‐MAC) of the Aristotle University of Thessaloniki (Gkelis and Panou ), under white fluorescent light (20 μmol photons · m −2 · s −1 ) with a 12:12 h light:dark cycle at 20 ± 1.0°C.…”

“…; Table in the Supporting Information), as described in Konstantinou et al. (). The 16S‐23S Internal Transcribed Spacer (ITS) region, partial sequence of ribulose‐1,5‐bisphosphate carboxylase/oxygenase large subunit ( rbc L), partial rpo C1 gene (encoding the g subunit of RNA polymerase), and the nif H gene (nitrogenase reductase) were amplified from all strains using previously designed primers (Iteman et al.…”

“…According to the most recent review, cyanobacterial diversity reported from sponges is still underestimated; their taxonomy below the phylum level has received little attention (Konstantinou et al. ).…”

“…In Greece, the occurrence of more than 35 Leptolyngbya taxa has been reported from various habitats . Moreover, our recent research on sponge-associated cyanobacteria in the North Aegean Sea (Konstantinou et al 2018) showed novel cyanobacteria clades that deserved further investigation regarding their taxonomic status. The isolated Leptolyngbya-like strains, which were genetically diverse based on 16S rRNA gene phylogeny, were thoroughly analyzed in the present study using morphological characters (LM and TEM observations), phylogeny of four molecular markers, ITS secondary structure as well as ecological and biochemical characters.…”