Microflora of Giant Duckweed

Baker, Stokes, Sameh Shella, and Mona Hammoud

Giant duckweed (Spirodela polyrhiza) is a common aquatic plant that is used for phytoremediation and is a major food source for many animals. The role that the associated microbial communities play in the plant's ability to acquire nutrients is not well understood. Fluorescent staining with SYTO9 showed that a microflora is present on the roots and fronds of S. polyrhiza. To determine what bacteria are part of the microflora, a metagenomic approach was used. Metagenomics, utilizes the power of next generation sequencing to identify species by sequencing DNA isolated from environmental samples. The microflora growing on S. polyrhiza collected from Lake Saint Clair (Harrison Township, Michigan, USA), was isolated by treating the plants with a multi-enzyme solution designed to remove biofilms. Total microbial DNA was isolated, and the Variable Region 4 found in the 16S rRNA genes was sequenced using an Illumina (San Diego, CA) MiSeq platform. Over 1400 species of bacteria were identified, based on the homology found in the small subunit rRNA SILVA database (Microbial Genomics and Bioinformatics Research Group, Bremen, Germany). Principle component analysis indicates that there are distinct differences between the bacterial community growing on giant duckweed, and the bacteria suspended in water.