Mapping the Molecules Made by a Lichen’s Resident Microbes

An international team of researchers has spatially mapped molecules produced by an intact, complex microbial community for the first time. Using a tiny slice of lichen, the team used imaging mass spectrometry to track and plot metabolites made by both bacterial and fungal lichen members. Their approach, published online on December 20, 2016 in mSystems®, an open-access journal of the American Society for Microbiology, shows how researchers can tease apart the chemistry that shapes and maintains a complex, three-dimensional microbial community. The article is titled “Spatial Molecular Architecture of the Microbial Community of a Peltigera Lichen.” "Until now, there had not been a single microbial community studied from the chemical standpoint--particularly how they are organized with respect to the molecules being produced," says Pieter Dorrestein, Ph.D., Chemistry Professor in the University of California, San Diego School of Pharmacy and senior author on the study. The team, which included researchers from the US, Canada, Germany, and Russia, chose the Peltigera hymenina lichen, which lives in humid environments on soils in forests and roadsides, as a test-bed community. Using a postage-stamp-sized sample of the lichen collected in British Columbia, Canada, the team first analyzed the relative abundance of all known genes present and found that the lichen was made up of about 81% bacteria (including cyanobacteria) 0.001% archaea, and about 19% eukaryotes (including fungi). More than 75,000 of those genes, or 13% overall, were found to be for enzymes involved in producing secondary metabolites. These metabolites "are really responsible for driving and shaping the microbial community," Dr. Dorrestein says.
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