Complex phyllosphere microbiome aids in the establishment of the invasive macrophyte Hydrilla verticillata (L.) under conditions of nitrogen scarcity

Despite the low availability of nitrogen (N), the highly productive macrophyte Hydrilla verticillata (L.) is a successful invader of the littoral zones at lake Atitlan, Guatemala, with profound implications for lake ecology. To help answer the question of how Hydrilla, accompanied by the filamentous green alga Cladophora Kutzing (Ulvophyceae), sustains fast growth under conditions of N scarcity, we studied the composition and potential biogeochemical function of the associated microbiomes. We combined results from next generation sequencing of associated bacterial and fungal assemblages with traditional microscopy-based taxonomical evaluation of algae and cyanobacteria. We focused on the presence of specific N2-fixing genera and their relative importance. Data on community composition are complemented with measurements of diazotrophic activity. The results expand our knowledge of the ecophysiology of these algae-plant-microbe consortia and suggest that several levels of biological complexity should be considered to fully understand aquatic plant ecology and the process of macrophyte invasions.