A comparative analysis of the microbial community structure and functional gene profile between healthy and diseased...

Marine macroalgae and their associated microbial communities are pivotal in shaping coastal ecosystems and facilitating biogenic elements' biochemical cycles. In this study, we implemented the high-throughput sequencing technology to sequence bacterial 16S rRNA gene to comprehensively analyze the bacterial communities of healthy and diseased macroalgae as well as the surrounding seawaters. The results revealed that Proteobacteria and Bacteroidota were the two main phylum in all samples. Alphaproteobacteria, Gammaproteobacteria and Bacteroidota were the predominant bacterial classes. This observation underscored that the composition of bacterial communities remains comparably consistent at higher taxonomic levels, regardless of variations in their health statuses. The alpha-diversity indices of seawater bacterial communities, epiphytic communities, and endophytic communities showed no significant differences. Epiphytic bacterial communities harbored a greater proportion of colonized bacteria, such as Vibrio and Pseudomonas. While endophytic bacterial communities contained a higher presence of tissue-degrading microbial assemblages, the primary bacterial communities were predominantly affiliated with Rhodobacteraceae and Flavobacteriaceae. Temperature, salinity, nitrate and nitrite concentration were the most significant properties correlated with seawater, epiphytic and endophytic bacterial communities in different health statuses revealed by Canonical correspondence analysis. A PICRUSt analysis demonstrated the metabolic functional prediction. Nitrogen and sulfate reduction genes were mainly concentrated in epiphytic bacterial communities in good health. Endophytic bacterial communities in disease had higher carbon and nitrogen fixation potentials. These results confirmed that bacteria, macroalgae, and environmental properties had an interactive relationship, all related to the momentous ecological benefits of macroalgae.