Comparison of bacterial communities among geographically distinct populations of the benthic dinoflagellate Prorocentrum lima

Members of the Prorocentrum lima species complex (PLSC) are most frequently found in high cell abundance in the tropics and sub-tropics and are almost invariably toxigenic. Epiphytic and planktonic bacteria are known to co-occur with such toxigenic Prorocentrum but reciprocal allelochemical interactions with the dinoflagellate microbiome have been under-investigated and are poorly understood. The aim of the present study was to identify and compare the bacterial community cultured together with isolates of the PLSC from geographically distant coasts of Mexico. Profiles of bacterial communities associated with dinoflagellate clones were obtained by high-throughput sequencing of 16S V3-V4 amplicons. Our results show that the microbiome of P. lima is associated with the location of origin. A similar bacterial diversity was found free-living in culture medium or closely associated with the host dinoflagellate cells. The microbiome comprised a total of fourteen bacterial classes where alpha- and gammaproteobacteria and Bacteroidia dominated the respective communities. Specifically, members of genera Labrenzia, Roseitalea, Cohaesibacter, Marivita, Muricauda, Marinobacter and Masilia were most abundant. Based on known interactions of these genera with other microeukaryotes, they may sustain symbiotic relationships with P. lima populations via a variety of allelochemicals and reciprocal nutrient enrichment mechanisms within the phycosphere. Bacterial members identified will improve the study of the toxigenicity, ecology, and biotechnological potential of this benthic dinoflagellate group