The composition, function and assembly mechanism of epiphytic microbial communities on Gracilariopsis lemaneiformis

Gracilariopsis lemaneiformis is effective for bioremediation and important ecologically and economically in coastal ecosystems. However, little is known about the epiphytic microbes on it. We used the 16S rRNA gene and ITS amplicon sequencing, and a comprehensive functional gene array (GeoChip 5.0) to analyze both the epiphytic microbial communities on G. lemaneiformis and the free-living microbial communities in the surrounding seawater. The dominant epiphytic taxa, Aquimarina, Leucothrix, Formosa and Croceitalea, are associated with the seaweed and the degradation of algal polysaccharides. Genes enriched in the epiphytic community contribute to the seaweed surface life stress responses, quorum sensing, formation and stabilization of biofilms and antifouling. Moreover, homogeneous selection was the predominant deterministic process of epiphytic microbial community assembly. Our study provides new insights into understanding the G. lemaneiformis epiphytic communities and proposes guidance for future studies of other microbe-seaweed interactions in order to uncover the ecological mechanisms of epiphytes.