On microbial community of Pyropia haitanensis by metagenomic analysis

Microorganisms plays an important role in the growth of Pyropia haitanensis. To understand the structural and functional diversity of the microorganism community of P. haitanensis (PH40), the associated metabolic pathway network in cluster of orthologous groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG), and carbohydrate-active enzymes (CAZymes) were explored in metagenomic analysis. DNA extraction from gametophytes of P. haitanensis was performed first, followed by library construction, sequencing, preprocessing of sequencing data, taxonomy assignment, gene prediction, and functional annotation. The results show that the predominant microorganisms of P. haitanensis were bacteria (98.98%), and the phylum with the highest abundance was Proteobacteria (54.64%), followed by Bacteroidetes (37.92%). Erythrobacter (3.98%) and Hyunsoonleella jejuensis (1.56%) were the genera and species with the highest abundance of bacteria, respectively. The COG annotation demonstrated that genes associated with microbial metabolism was the predominant category. The results of metabolic pathway annotation show that the ABC transport system and two-component system were the main pathways in the microbial community. Plant growth hormone biosynthesis pathway and multi-vitamin biosynthesis functional units (modules) were the other important pathways. The CAZyme annotation revealed that the starch might be an important carbon source for microorganisms. Glycosyl transferase family 2 (GT2) and glycosyl transferase family 3 (GT3) were the highly abundant families in glucoside transferase superfamily. Six metagenome-assembled genomes containing enzymes involved in the biosynthesis of cobalamin (vitamin B12) and indole-3-acetic acid were obtained by binning method. They were confirmed to belong to Rhodobacterales and Rhizobiales, respectively. Our findings provide comprehensive insights into the microorganism community of Pyropia.