Using a Control to Better Understand Phyllosphere Microbiota.

An important data gap in our understanding of the phyllosphere surrounds the origin of the many microbes described as phyllosphere communities. Most sampling in phyllosphere research has focused on the collection of microbiota without the use of a control, so the opportunity to determine which taxa are actually driven by the biology and physiology of plants as opposed to introduced by environmental forces has yet to be fully realized. To address this data gap, we used plastic plants as inanimate controls adjacent to live tomato plants (phyllosphere) in the field with the hope of distinguishing between bacterial microbiota that may be endemic to plants as opposed to introduced by environmental forces. Using 16S rRNA gene amplicons to study bacterial membership at four time points, we found that the vast majority of all species-level operational taxonomic units were shared at all time-points. Very few taxa were unique to phyllosphere samples. A higher taxonomic diversity was consistently observed in the control samples. The high level of shared taxonomy suggests that environmental forces likely play a very important role in the introduction of microbes to plant surfaces. The observation that very few taxa were unique to the plants compared to the number that were unique to controls was surprising and further suggests that a subset of environmentally introduced taxa thrive on plants. This finding has important implications for improving our approach to the description of core phytobiomes as well as potentially helping us better understand how foodborne pathogens may become associated with plant surfaces.