Co-monitoring bacterial and dinoflagellates communities by denaturing gradient gel electrophoresis(DGGE) and SSU rRNA sequencing during a dinoflagellates bloom

Dinoflagellates are unicellular eukaryotic protists that dominate in all coastal waters,and are also present in oceanic waters.Despite the central importance of dinoflagellates in global primary production,the relationship between dinoflagellates and bacteria are still poorly understood.In order to understand the ecological interaction between bacterial and dinoflagellates communities,denaturing gradient gel electrophoresis(DGGE) and SSU rRNA sequencing were applied to monitoring the population dynamics of bacteria and dinoflagellates from the onset to disappearance of a dinoflagellates bloom occurred in Baltimore Inner Harbor,from April 15 to 24,2002.Although Prorocentrum minimum was the major bloom forming species under the light microscopy,DGGE method with dinoflagellate specific primers demonstrated that Prorocentrum micans,Gymnodinium galatheanum and Gyrodinium uncatenum were also present during the bloom.Population shifts among the minor dinoflagellate groups were observed.DGGE of PCR-amplified 16S rRNA gene fragments indicated that cyanobacteria,α,β,γ proteobacteria,Flavobacterium-Bacteroides-Cytophaga(FBC),and Planctomcetes were the major components of bacterial assemblages during the bloom.DGGE analysis showed that Cytophagales and α-proteobacteria played important roles at different stages of dinoflagellates bloom.DGGE can be used as a rapid tool to simultaneously monitor population dynamics of both bacterial and dinoflagellates communities in aquatic environments,which is demonstrated here.