"Besides the importance of these bacteria in ecosystem stability, they can also be sources of biochemical compounds for the pharmaceutical industry and agriculture," says Marcio Lambais of the University of Sao Paulo in Brazil, whose team published their results in today's issue of Science.
The scientists conducted their survey by collecting 20 to 30 leaves from each of nine different tree species throughout the forest. In the lab, the researchers processed about 12 grams of leaves from each tree at a time, rinsing them in special solution that dislodged surface microbes. They analyzed the DNA from the microbes to get a general view of how similar the communities in different trees were to each other. From there, they selected two tree species that hosted similar bacterial communities and one species that contained a very distinct community. They sequenced fragments of DNA from the microbes to get a more detailed picture of the different bacteria present and to estimate the diversity in the forest.
The team found that even trees of the same species had some variation when it came to the bacterial communities living on their leaves, but there was significantly more variation among trees of different species. Calculations indicated that each tree could harbor anywhere between 95 to 671 different species of bacteria. And when the scientists extrapolated the number to include all leafy surfaces, they came up with 2 million to 13 million new bacterial species.
"We were quite surprised and euphoric when we extrapolated the figures. We suspected that the diversity would be high, but not that high. Now we need to understand how these communities function and their roles in the ecosystem," Lambais remarks. He and his team are currently studying the diversity of bacteria on the leaves of seven more tree species from another location in the forest. By looking at a higher number of individual trees, they hope to gain a better understanding of, among other things, whether the bacterial communities are affected by the location of their host tree.