Duckweed hosts a taxonomically reduced bacterial assemblage.

Plant microbiota provide many benefits to the plant host including growth promotion and disease protection. While many plant microbial community profiling studies have been conducted on terrestrial plants much less is known about the aquatic plant microbiome. Duckweed is a small aquatic plant that holds many characteristics, including small size, reduced plant architecture, and aquatic habitat, that suggest its use as a facile model system for plant microbiome studies. We present here a comprehensive analysis of the duckweed bacterial microbiome from different environments. First, a culture-independent survey of the duckweed bacterial microbiome from different locations in New Jersey revealed similar phylogenetic profiles with minor qualitative differences. However, major differences in relative abundance of community members were observed between sites. These studies also showed Proteobacteria is a dominant phyla in the duckweed bacterial microbiome. To observe the assembly dynamics of the duckweed bacterial community, we inoculated quasi-gnotobiotic duckweed with wastewater effluent from a municipal wastewater treatment plant. Results revealed that duckweed strongly shapes its assembled bacterial microbiome and forms distinct associations with bacterial community members from the initial inoculum. Additionally, these inoculation studies showed the bacterial communities of different duckweed species contain a highly similar phylogenetic structure. Analysis of the duckweed bacterial community across several different studies identified a set of “core” bacterial genera consistently present on duckweed irrespective of the locale and context. Taxonomic comparison of the duckweed bacterial community to that in rice and Arabidopsis suggests lower complexity in duckweed. Our results indicate duckweeds utilize similar bacterial community structuring principles as those found in terrestrial plants while hosting a less diverse bacterial community. The information presented in this study will help inform the design of future experimental studies aimed at understanding plant microbial community establishment with the goal of leveraging plant-microbe interactions for improved growth performance.