Evaluating the quorum quenching potential of bacteria associated to Aurelia aurita and Mnemiopsis leidyi

The associated microbiota of marine invertebrates plays an important role to the host in relation to fitness, health and homeostasis of the metaorganism. As one key chemically-mediated interaction, Quorum sensing (QS) and interference with QS among colonizing bacteria ultimately affects the establishment and dynamics of the microbial community on the host. Aiming to address interspecies competition of cultivable microbes associated to merging model species of the basal animal phyla Cnidaria (Aurelia aurita) and Ctenophora (Mnemiopsis leidyi) as well as to evaluate their potential to shape the associated community by interfering with QS, we performed a classical isolation approach. Overall, 84 bacteria were isolated from A. aurita medusae and polyps, 64 bacteria from M. leidyi, and 83 bacteria from the ambient seawater, followed by taxonomically classification by full length 16S rRNA gene analysis. The results show that the moon jellyfish A. aurita and the comb jelly M. leidyi harbor a cultivable core microbiota consisting of typical marine and ubiquitously found bacteria (e.g. Chryseobacter, Microbacterium, Micrococcus, Olleya, Phaeobacter, Pseudoalteromonas, Pseudomonas, Rhodococcus, Shewanella, Staphylococcus, and Vibrio) which can also be found in the ambient seawater. However, several bacteria were restricted to one host (e.g. for A. aurita: Bacillus, Glaciecola, Ruegeria, Luteococcus; for M. leidyi: Acinetobacter, Aeromonas, Colwellia, Exiguobacterium, Marinomonas, Pseudoclavibacter, Psychrobacter, Sagittula, Thalassomonas) suggesting host-specific microbial community patterns. Evaluating QQ activities, out of 231 isolates, 121 showed QS-interfering activity. They mainly interfered with the acyl homoserine lactone (AHL) based communication, whereas 21 showed simultaneous quorum quenching activities against AHL and autoinducer-2. Overall, this study provides insights into the cultivable part of the microbiota associated to two environmentally important marine non-model organisms and discloses their potential in synthesizing QS interfering compounds, potentially important in shaping a healthy and resilient microbiota.