Hyunsoonleella sp. HU1-3 Increased the Biomass of .

Green algae are photosynthetic organisms and play an important role in coastal environment. The microbial community on the surface of green algae has an effect on the health and nutrition of the host. However, few species of epiphytic microbiota have been reported to play a role in promoting the growth of algae. In this study, 16S rDNA sequencing was used to study the changes of microbial composition on the surface of at different growth stages. Some growth promoting bacteria were identified. The possible growth-promoting behavior of the strains were verified by co-culture of pure bacteria obtained from the surface of with its sterile host. Among the identified species, a new bacterial species, sp. HU1-3 (belonging to the family Flavobacteriaceae) significantly promoted the growth of . The results also showed that there were many genes involved in the synthesis of growth hormone and cytokinin in the genome of sp. HU1-3. This study identified the bacterium sp. HU1-3 for the first time, in which this bacterium has strong growth-promoting effects on . Our findings not only provide insights on the establishment of the surface microbiota of , but also indicate that sp. HU1-3 is one of the important species to promote the growth of .