Investigation of phyllosphere Microorganism-Azolla Interaction: Insights into Incidence Rates and Metagenomic Analysis

Abstract Background: Azolla is a versatile aquatic fern that is rich in nutrients and possesses valuable antibacterial components, making it a useful green manure and medicinal raw plant material. However, the growth of Azolla is affected by microorganisms under different environmental conditions, the investigation on the interaction between microorganisms and Azolla is one of the crucial projects for Azollaexploration and application. Results: In this study, we cultivated two different Azolla species, Azolla imbricata (Aim) and Azolla pinnata (Api), under identical condition to investigate their respective incidence rates. Metagenome analysis of phyllosphere microorganisms was performed to uncover the interaction between Azollaand microorganisms. Our results revealed significantly higher incidence rates in Aim compared to Api. The microbiological community taxonomy showed a predominance of Proteobacteria phylum and Burkholderiales order, with higher proportions in the Aim group. Conversely, the Api group had higher proportions of Cyanobacteria phylum, Nostocales order, Nostocaceae family, and Trichormusgenus. Moreover, pathogenic bacteria exhibited a higher relative abundance in the Aim group. We further analyzed significant differences in KEGG pathways between the two groups and identified the top 10 enriched pathways. Additionally, according to the resistance gene analysis results, five resistant genes showed different patterns between Api and Aim groups. Expect AAC6-IIa, the other five resistant genes had a higher abundance in Aim than in Api. Conclusions: The greater disease susceptibility of Aim compared to Api may be linked to the microbial community structure of the two species. The variations in microbial community structure could be influenced by the antibacterial components present in Api, whereas Aim may lack or have lower levels of these antibacterial components.These findings provide insights into the microorganisms-Azolla interaction, aiding the development of strategies to enhance Azolla growth and utilization.