Around a single algae cell, there usually exists a special microenvironment called “phycosphere” inhabited by specific microbial communities. While bacteria-algae interactions in the phycosphere occur within an inherently microscale context, they may often have cascading bottom-up influences on ecosystem-scale processes. Currently, the formation mechanism of microbial communities in the phycosphere is still uncertain. In this study, we isolated five Skeletonema tropicum and one Skeletonema menzelii, and the 16S rRNA amplicons sequencing of phycosphere bacteria at different growth stage was carried out. The results show that, the phycosphere of different strains of Skeletonema was dominated by different bacterial groups, which were primarily composed of members belonged to the Alphaproteobacteria and Gammaproteobacteria. Among them, Rhodobacteraceae un. and Alteromonas were the core genera (consistently existing in all six Skeletonema), and Marivivens, Rhodovulum, Neptuniibacter and Marinobacterium were the dominant genera (consistently existing in 4 ~ 5 strains of Skeletonema). Meanwhile, the bacterial communities in the phycosphere of the same strains of Skeletonema undergo dynamic succession during different growth stages. The potential functions of phycosphere bacterial communities of Skeletonema was mainly related to metabolism, including amino acid metabolism, carbohydrate metabolism, lipid metabolism, and xenobiotics biodegradation and metabolism. Our results indicated that although the composition of bacterial communities in the phycosphere of different strains of Skeletonema, their functions were similar.

Skeletonema, phycosphere, bacterial communities