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.