Authors: Robin Tecon, Annemieke van der Wal, Mitja Remus-Emsermann and Johan Leveau. Background: In microbial ecology, the study of bacteria is traditionally limited to the level of populations. Natural habitats, however, consist of connected microenvironments with highly variable life conditions (nutrients, water, pH, etc.), in which bacterial individuals experience different local interactions with each other and their environment. For instance, the surface of plant leaves (the phyllosphere) provides microheterogeneity and is typically inhabited by a wide variety of bacteria. Erwinia herbicola 299R (Eh299R), a natural leaf colonizer, was used as a model strain in a new experimental set-up that aims at a better understanding of the individuality component of the surface-colonization by bacteria. Methods: Eh299R was tagged with a gene encoding a variant of the green fluorescent protein (GFPmut3), either constitutively expressed or as an inverse function of the reproductive success of the bacteria over time. Bacterial cells were inoculated to the surface of a defined agarose gel medium or on bean leaves. Fluorescence microscopy coupled with image cytometry was used to investigate the growth of the colonizer cells during incubation. Results: Individual Eh299R cells grew homogenously to form microcolonies on the surface of a defined gel medium. The same bacteria, however, varied in growth rate when a nutrient gradient was applied to the gel. Using fluorescence intensity measurement, it was possible to quantify the reproductive success of individual bacteria within microcolonies. In parallel, an agent-based model was used to predict the growth of individual bacteria in silico. Finally, GFP-tagged Eh299R were also inoculated on bean leaves to observe their distribution in situ. Conclusion: Fluorescent bacterial strains derived from Eh299R can efficiently be used to study the growth fate of surface colonizers at the individual cell level, and can be used to improve models of phyllosphere colonization by bacteria.
|Publication status||Published - 2010|