Species-level profiling of Landoltia punctata (duckweed) microbiome under nutrient stress using full-length 16S rRNA sequencing

Duckweed is a rapidly-growing aquatic plant utilized as food/feed and for wastewater remediation. It coexists with complex microbial communities that play crucial roles in its growth and capability for phytoremediation. In a previous study, microbiomes associated with four duckweed species ( Spirodela polyrhiza , Landoltia punctata , Lemna aequinoctialis , and Wolffia globosa ) grown under natural and nutrient-deficient conditions, were investigated using V3V4 16S rRNA sequencing. However, species-level classification was not achieved due to the partial 16S rRNA sequences obtained, restricting the selection of potential microbial species for further application. In this study, L. punctata samples from the previous work were investigated further by employing full-length 16S rRNA sequencing. A total of 31 predominant microbial species were identified. Under stress, the proportion of Proteobacteria increased significantly, along with potentially beneficial bacteria such as Roseateles depolymerans , Pelomonas saccharophila , Acidovorax temperans , Ensifer adhaerens and Rhizobium straminoryzae . Functional metagenomic predictions suggest that associated microbes adapt to stressors and may confer benefits to duckweed, including pathways related to host adhesion, biofilm formation, microbial growth modulation, and co-factors and vitamin biosynthesis. Furthermore, the study demonstrates both the advantages and limitations of full-length 16S rRNA amplicon sequencing. The findings provide more insight into L. punctata microbiomes at species-level, facilitating establishment of stable, beneficial microbial communities for duckweed applications. Ongoing investigations aim to isolate key microbial species from L. punctata and validate their roles through co-cultivation, along with establishing potential synthetic microbial communities based on the metagenomic findings.