Identifying Trees by their Bacteria

New research has confirmed that trees can be identified by certain types of bacteria found on their leaves, kind of like their own genetic fingerprint, so to speak. This in turn can help scientists better understand how to best sustain biological diversity and ecosystem function.

"This study demonstrates for the first time that host plants from different plant families and with different ecological strategies possess very different microbial communities on their leaves," study lead author Steven W. Kembel said in a press release.

A team from the University of Oregon studied bacterial samples from 57 of the more than 450 tree species growing in a lowland tropical forest on Barro Colorado Island, Panama.

Using DNA sequencing, they focused on the bacterial 16S ribosomal RNA gene - also called the barcode gene - which allowed the researchers to identify the bacteria unique to certain tree species among millions of bacteria present on their leaves.

"Some bacteria were very abundant and present on every leaf in the forest, while others were rare and only found on the leaves of a single host species," Kembel explained. "Each tree species of tree possessed a distinctive community of bacteria on its leaves."

Plant leaves host millions of types of bacteria, some of them good and some of them bad. For instance, some bacteria on leaves can cause disease while others can actually protect the plant from harmful pathogens or even promote plant growth.

Among the many types of bacteria found, some of the most common included Actinobacteria, Alpha-, Beta- and Gamma-Proteobacteria and Sphingobacteria. In addition, some types of bacteria, according to researchers, were more abundant when growing on the leaves of fast-growing or slow-growing tree species, or on leaves with different concentrations of elements such as nitrogen or phosphorus.

"Ultimately, we hope that understanding the factors that explain variation in bacterial abundances across host species will help us better manage biological diversity in forests and the health and function of forest ecosystems," Kembel added.

The findings were published in the journal Proceedings of the National Academy of Sciences.