Dr-Elaine-InghamProf. Julia Vorholt, Institute of Microbiology at ETH Zurich

“One to ten million unicellular microorganisms live on every square centimeter of stems and foliage making the phyllosphere “the largest biological surface inhabited by microorganisms”, explains Prof. Julia Vorholt at the Institute of Microbiology at ETH Zuric.

Gerd Innerebner and Roger Wepf/ETH Zurich

In recent years new investigative tools from microbiology have made it possible to gain a better insight into microorganisms and their function in complex microbe communities. “Two kinds of bacteria dominate this ecosystem, members of the Methylobacterium genus and unicellular organisms from the Sphingomonas genus. ”, says Vorholt. No matter what plant they studied, microbes from the sphingomonas and methylobacterium genera and their proteins always dominated the scenery. These researchers found over twenty five bacteria genera with more than a hundred species, living on plant leaves. The researchers in Switzerland also discovered previously unknown proteins, “which appear to be important for most bacteria on the leaves of plants”, says Julia Vorholt. What they found was Methylobacteria converting methanol produced by the plants into CO2 for energy. “It is perfectly feasible that the colonization by microbes like methylobacteria or sphingomonas could protect the plants from such attacks…. the bacteria even produce antibiotics to keep the plants healthy”, says Julia Vorholt.