The study of natural biofilm formation and microbial community structure for recirculating aquaculture system

Abstract

Biofilter is the core unit of the recirculating aquaculture system(RAS), which is mainly to achieve in situ purification and restoration of water pollutants by enriching microorganisms on biofilters to form biofilms. To explore the changes and metabolic characteristics of microbial communities in the process of biofilm formation in the RAS under low-temperature environment, the 16S rRNA high-throughput sequencing was applied to analyze differences of the microbial composition and structural characteristics in the biofilm initiation group (I) and biofilm formation group(B), and the PICRUSt functional gene prediction method was used to predict the metabolic functions. Results of microbial diversity showed that the OTUs numbers, Shannon index and richness index increased significantly after bio-film formation(p<0.05). The Pcoa results indicated that the microbial community composition in group B was quite different compared with the group I. After the biofilm formation, the phylum Proteobacteria, Bacteroidota, Fusobacteriota, Patescibacteria and Verrucomicrobiota were the main dominant bacteria on the biofilter. The denitrifying bacteria, such as Comamonadaceae and Rhodobacteraceae as the dominant bacteria in group B. Meanwhile, the activities of bio-film microorganisms in metabolic aspects of Carbohydrate Metabolism, Energy Metabolism, Lipid Metabolism, Amino Acid Metabolism of Terpenoids and Polyketides and Enzyme Families were obviously enhanced(p <0.05).