Comparison of bacterial communities associated withProrocentrum donghaienseandKarenia mikimotoistrains from Chinese coastal waters

The dinoflagellatesKarenia mikimotoi(toxic) andProrocentrum donghaiense(non-toxic) have caused serious blooms in Chinese coastal waters. Although many studies have investigated the mechanisms underlying the harmful algal blooms of these two species, research on bacterial communities associated withK. mikimotoiandP. donghaienseis still limited. In this study, the composition of associated bacterial communities ofK. mikimotoiandP. donghaiensewere investigated in cultured strains. The genera with the highest relative abundance inK. mikimotoiandP. donghaiensecultures wereBalneolaandMarinobacterrespectively. There were 26 genera specifically present inK. mikimotoicultures, includingAlteromonas,MethylophagaandThalassospira. Sixteen genera were specifically present inP. donghaiensecultures, including an unclassified genus belonging to Nannocystaceae,LoktanellaandRoseivirga. Various aromatic hydrocarbons capable of degrading bacteria were detected in theK. mikimotoiculture, but not in theP. donghaienseculture; this may contribute to the toxicity or toxin synthesis ofK. mikimotoi. The results of this study provide further insights into bloom formation mechanisms and elucidate the different characteristics ofK. mikimotoiandP. donghaienseblooms.