Steve Lindow (UCB) talking about colonization of leaf surfaces by airborne bacteria

This June, I was able to attend the 2015 Phytobiomes meeting in Washington D.C. I am originally from the Washington DC area, so it was really nice to go to a meeting and see my family at the same time.

The Phytobiomes Initiative is a collaboration between APS and other groups in an effort to understand how microbes influence the growth and health of plants as a whole. As plant pathologists, we obviously care about what microbes make plants sick, but this initiative wants to explore both healthy and sick plants, and look at how to direct the microbial populations to support healthier plants. To do this, they have invited speakers from many different areas, including human health, seed protection, and agriculture to speak on how they have explored these topics.

I have recently begun to research how biofungicides and downy mildew disease affect the microbial communities on the phyllosphere of spinach. This is a rich and emerging area within plant pathology that has recently had a re-emergence with the reduction in costs for next generation sequencing. Our department’s Johan Leveau is leading the charge on exploring how non-pathogens play a role in the colonization and exclusion of plant pathogenic microbes. Neil and I began this project alongside Johan and Nilesh Maharaj (Johan’s grad student) because there is very little information about how disease or biofungicides impact phyllosphere communities. This is especially relevant in spinach, a crop in which the entire above-ground portion is eaten.

One thing that struck me about the meeting was the need for applications of epidemiology to microbial ecology research. When plants emerge from their seeds, they are (relatively) sterile. Recent research has shown that there is very little overlap between soil microbes and the microbes that eventually colonize the leaf and root surfaces. Where do the colonizers come from? Tracking the dispersal and spread of colonizers is a classic problem for epidemiologists. While plant disease epidemiology is a bit easier (you can simply look for symptoms), I believe that the basic processes that we have described for epidemics will be applicable here.

Our own research will probably fall a bit short of this lofty goal though, as our objective was to describe what organisms were present under different conditions. However, the area of non-pathogen forensics is ripe for epidemiology. In the future, I would like to combine our epidemiological knowledge of colonization and weather conditions with our knowledge of microbial ecology.

Its a brave new world out there and we are only beginning to scratch the surface.