they can also be used to antagonize fish-pathogenic bacteria without harming the fish or their live feed. since roseobacter has such high abundances, accounting for 15 to 20% of oceanic bacterio-plankton communities, they can be used for establishment of synthetic biology chassis for bio-geoengineering activities such as bioremediation of oceanic waste plastic. quorum sensing most bacteria have chemical communication systems. quorum sensing (qs) is a process by which bacteria sense and perceive their own population density through diffusible signals. in the members of the roseobacter clade, acyl-homoserine lactone (ahl)-based quorum sensing is widespread: over 80% of available roseobacterial genomes encode at least one luxi homologue. this shows the significant role of qs controlled regulatory pathways plays in adapting to the relevant marine environments. among all the available roseobacterial ahl-based qs, three are most well studied: phaeobacter inhibens dsm17395, the marine sponge symbiont ruegeria sp. klh11 and the dinoflagellate symbiont dinoroseobacter shibae. however, to understand more fully the ecological role of qs mechanisms, further studies on qs and the signalling process in a greater diversity of roseobacters is needed.