Abstract
Sphingomonas is one of the most abundant bacterial genera in the phyllosphere of wild Arabidopsis thaliana, but relative to Pseudomonas, the ecology of Sphingomonas and its interaction with plants remains elusive. We analyzed the genomic features of over 400 Sphingomonas isolates collected from local A. thaliana populations, which revealed high intergenomic diversity, in contrast to genetically much more uniform Pseudomonas isolates found in the same host populations. Variation in Sphingomonas plasmid complements and additional genomic features suggest high adaptability of this genus, and the widespread presence of protein secretion systems hints at frequent biotic interactions. While some of the isolates showed plant-protective properties in lab tests, this was a rare trait. To begin to understand the extent of strain sharing across alternate hosts, we employed amplicon sequencing and a novel bulk-culturing metagenomics approach on both A. thaliana and neighboring plants. Our data reveal that Sphingomonas and Pseudomonas both thrive on other diverse plant hosts, but that Sphingomonas is a poor competitor in dying or dead leaves.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Additional experiments in Figure 3 (plant protection against Pseudomonas on soil) and Figure 6 (competition of Sphingomonas and Pseudomonas in whole leaves vs. macerated leaves). Corresponding editing of full manuscript text. Addition of some Supplementary Figures
