Toxic and non-toxic dinoflagellates host distinct bacterial communities in their phycospheres

Abstract

Dinoflagellates encompass highly abundant and diverse toxin-producing species among marine phytoplankton. Previous works suggested that some bacterial taxa may affect toxins production in dinoflagellates, however, little is known about impact of toxic dinoflagellates on their co-existing bacterial flora. Here we characterized the bacterial communities associated with 22 clonal cultures of dinoflagellates using DNA metabarcoding method, including 11 confirmed toxic species and 11 species that have not been reported to be toxic. Beta diversity analysis revealed that all the 11 species in toxic group were clustered together and distinctly separated from non-toxic group, strongly suggesting the bacterial community composition was largely influenced by toxic dinoflagellate hosts. The toxic group was found to include higher relative abundance of non-carbohydrate utilizers and xenobiotic-degrading taxa and showed inhibitory effects on algicidal bacteria. These findings suggested that toxic dinoflagellates host bacterial communities distinctive from non-toxic species in multiple ways in their phycospheres.