Transitions of the Bacteria-Fungi Microbiomes Associated with Different Life Cycle Stages of Dinoflagellate .

Dinoflagellates significantly contribute to the carbon fixation and microbial loop in the ocean with high ecological diversity. While the microbial communities associated with the HABs of dinoflagellates have attracted intensive attention in recent years, little attention has been paid to the microbiomes associated with resting cysts, an important stage in the life cycle and bloom initiation dynamics of dinoflagellates. Using as a representative of cyst producers and cyst-relevant research in dinoflagellates, we surveyed the bacteria and fungi microbiomes long associated with different life cycle stages of the dinoflagellate culture through 16S and ITS rRNA amplicon sequencing, and predicted their possible functions using the PICRUSt2 algorithm. The results found high species diversity of the associated bacteria-fungi microbiomes, and species featured with diverse and flexible metabolic capabilities that have stably co-occurred with the laboratory culture of . The host-attached and the free-living groups of bacteria-fungi microbiomes, as operationally defined in the context, showed significant differences in terms of their nutritional preferences. The bacteria-fungi species diversity and community structure associated with cysts are also distinguished significantly from that with vegetative cells, with the latter attracting more bacteria-fungi species specializing in phosphate solubilization. These results suggest that the relative species abundance and thus the community structure of the host-associated microbiome shift with the transition of life cycle stages and environmental conditions. Our findings show the association tightness between bacteria-fungi microbiomes and dinoflagellate hosts and the different life stages of hosts shaping the bacteria-fungi communities, which result in dynamic and specific interactions between bacteria-fungi microbiomes and their hosts.