Monday, November 04, 2013

Modelling the bacterial colonization of leaves

Photo courtesy of Jan Tech
Our world is a quite green world: a sea of trees, bushes, grasses, or, if you happen to live in the Midwest, corn fields… What is less obvious, though, is the fact that this green vastness harbors a huge community of microbes. Yeasts and filamentous fungi are often found on plant surfaces, but the most numerous inhabitants are first and foremost bacteria. Indeed, a centimeter square of leaf can contain as many as 10 millions of them! No worries, most of them are harmless to us or their plant hosts. On the contrary, many are required to maintain a healthy plant environment, by stimulating plant growth or by preventing the plant colonization by pathogens (they compete for the same space and the same resources). 

Because plants are so vital to us (think food, raw materials, landscapes, etc.), there is a real interest in understanding what the microbial contribution to the plant ecosystem is. One lingering question, for instance, is how bacteria colonize the surface of leaves (what we call the phyllosphere). What we do know is that bacteria on leaf surfaces appear as clusters of cells, rather than an even layer of bacteria covering the surface; the mechanisms that lead to this colonization pattern, however, is not well understood. I have already written about this question in a previous post that dealt with the use of bacterial bioreporters. Another way to explore these mechanisms of cluster formation is computer-based modelling, which enables us to test different scenarios and compare it with what has been observed on real plants.