Assessment of the phycosphere microbial dynamics of microbial community associated with red algae culture under different cultural conditions

During growth progress of algae, the algal–bacterial interactions play a major role in growth of algal. It is critical to understand the mechanisms of phycosphere, regarding their distribution under different environments. Therefore, here we examined the P. purpureum growth and its associated unique microbial community structures under different nitrogen sources at different days. The results revealed that KNO3 meritoriously increased the P. purpureum growth by 11.484 g/L, cellular cell bond polysaccharides by 4.03 mg/mL, soluble exopolysaccharides by 2.881 mg/mL as compared to NH4NO3 and NH4-CL sources. Furthermore, the relationship of the α-diversity index of microbial communities was high under the ammonia source during growth process which was observed at 16th day. The results of UniFrac statistical distance between or within the samples showed the significantly higher on the 16th day of growth stage under ammonia sources. The main bacterial families (Oxyphotobacteria, Bacteroidia, Alphaproteobacteria, Chloroplast, Cytophagales, and Phycisphaerales) were diverse significantly and strongly associated with P. purpureum over the different stages of growth, which contribute to their relative abundance increased substantially (78%). The unique operational taxonomic units (OTUs) were shared among Proteobacterai, Becteroidetes, and Firmicutes are most abundant phylum, with shares of 65%, at the genus level, Bacteroides, P. purpureum, and Algorisphages (20%) occupied the OTUs occurrence frequency. The Venn diagram shows that during growth, ammonia source on day 16 has the highest number of unique OTUs (3566), indicating the high degree of microbial diversity of the P. purpureum. These results allowed to identify the underlying mechanisms for these relationships of algae bacteria consortia, which is useful for the sustainable culture and production of high valuable products.