Quorum sensing (QS) allows bacteria to communicate and regulate gene expression in a population density dependent manner acting through the accumulation of signal molecules. Marine sponges can provide enclosed niches that favor the accumulation of these signals produced by the microbial symbionts. Microorganisms capable of QS have been previously isolated from marine sponges and few studies have reported the presence of signaling molecules in sponge extracts able to activate N-acyl-homoserine lactone (AHL) QS-biosensors. In this work we performed an in-depth systematic study on the presence of QS-signaling molecules in 15 marine sponge species from the Mediterranean and the Red Sea. We used thin-layer chromatographic assays based on the Agrobacterium tumefaciens (NTL4) reporter system to detect signal molecules and liquid chromatography in tandem with mass spectrometry detection (LC-MS/MS) analysis to determine whether the signal molecules detected by TLC were typical AHLs or AHL-mimic molecules. Our aims were to determine whether (i) QS signaling is common in marine sponges; (ii) the signal molecules are canonical AHLs or AHL-mimic molecules (iii) signal-profiles are sponge-species specific; (iv) sponge species signal-profiles change with season.
