Cobalt exposure induces the specific associated-bacterial microbiome potentially contributing to cobalt stress alleviation of the host dinoflagellate Scrippsiella acuminata

Dinoflagellates grow in tight association with the bacterial community, which exert impacts on the physiology and ecology of both partners. However, the changes of associated-bacterial microbiome with the physiologies of the host dinoflagellate under specific heavy metals (HMs) stress remain largely unknown. In this study, we characterized the bacterial microbiome associated with the laboratory-cultured dinoflagellate Scrippsiella acuminata, a cosmopolitan bloom-forming species, under different cobalt concentrations, via high-throughput sequencing of 16 S rRNA gene amplicons. The sequencing of a total of 72 Libraries generated 6,047,695 reads which were classified into 31 phyla, 97 classes, 215 orders, 367 families, and 782 genera. We found that cobalt stress could greatly affect the growth of S. acuminata as well as the ASV diversity and community composition of the associated bacterial community. Significant dose-dependent changes in the bacterial community were detected, which were found to be closely correlated with some specific bacterial genera. Excessive cobalt exerted significantly inhibitory effects on microalgae growth-promoting bacteria (Marinobacter, Roseobacter, Mameliella, Leifsonia, Roseovarius, and Stappia). A notable increase in the relative abundance of HM-resistant bacteria with siderophore-producing capacity (Alteromonas, Arthrobacter, Pseudoalteromonas, Brevundimonas, Staphylococcus, Microbacterium, and Bacillus) and/or HM bio-removal potential (Corynebacterium, Pseudomonas, Burkholderia, Rhodococcus, and Gemella) was detected upon elevated cobalt concentrations, which potentially contributed to the cobalt stress alleviation of the dinoflagellate host. Our work provided deeper insights into the relationship between the associated-bacterial assemblage and dinoflagellate, and also broadened the current knowledge pertaining to the potential contributions of bacterial microbiome to the HM tolerance of host alga.