Environmental Factors Shape the Epiphytic Bacterial Communities of Gracilariopsis Lemaneiformis

Abstract

Macroalgae host variety of symbionts on their surface which play critical role in their growth and development processes. Nevertheless, the complete understanding of this interaction of epiphytic bacteria and host algae is still in its infancy. This study comprehensively analyses epiphytic bacterial communities composition of red macroalga Gracilariopsis lemaneiformis and environmental factors such as nitrogen and phosphorus which shape the composition of epiphytic bacterial communities of G. lemaneiformis and variation of epiphytic bacterial communities composition at different geographical location. The composition and structure of epiphytic bacterial communities were characterized using high throughput sequencing data of the V3-V4 hypervariable region of 16S rRNA gene amplicon sequencing. The epiphytic bacterial communities composition data revealed that epiphytic bacteria varied significantly among three different geographic locations i) Nan’ao Island (NA) (ii) Lianjiang County (LJ) and iii) Nanri Island (NR) in China. Redundancy analysis (RDA) showed that the relative abundance of Bacteroidetes, Firmicutes, Verrucomicrobia and Epsilonbacteraeota at NR were strongly positively correlated with total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NO3-N), and dissolved inorganic nitrogen (DIN), whereas negatively correlated with nitrite nitrogen (NO2-N). In addition, the relative abundance of cyanobacteria at NA and LJ were strongly positively correlated with NO2-N, whereas negatively correlated with TN, TP, NO3-N, and DIN. Furthermore, the results of Mantel test indicated that the epiphytic bacterial communities composition is significantly correlated with these environmental factors, which are also proved by Pearson correlation analysis. In conclusion, it is proposed that environmental factors such as NO3-N and DIN play key role in the communities composition of epiphytic bacteria in G. lemaneiformis. Our study provides important baseline knowledge for the communities composition of epiphytic bacteria in G. lemaneiformis and their correlation among themselves as well as with their surrounding environmental factors.