To explain the variability in AHL presence in different T. swinhoei specimens, we tested the presence of the previously identified AHL producer, Rhodobacterales bacterium TS309 (Britstein, et al., 2015), in the same sponge individuals. Accordingly, we analyzed whether the relative abundance of TS309 corresponded to the presence of AHLs detected in the periodically sampled T. swinhoei.</p><p>The relative abundance of TS309 did not explain presence/absence of AHLs in different specimens of T. swinhoei analyzed (described in main text of manuscript). Accordingly we analyzed the microbiome structure in all specimens and tested whether positive AHL specimens were enriched in specific OTUs.</p><p>We investigated the structure of symbiotic microbial communities in different specimens of T. swinhoei and among different collection times, and compared it to the presence or absence of AHLs in the sponge extracts of the same specimens.