Dispersal and growth of bacteria

Abstract

Quantitative experiments with the ability to systematically probe the system under investigation are a key element to gain insight and understanding. We present a novel and simple technique enabling the maintenance and controlled perturbation of experimental conditions of microorganisms from bacteria to nematodes. Polyacrylamide-based devices are simple to fabricate from ingredients typically present in biolabs and are in addition biocompatible, permeable to small molecules and physically robust to even withstand adult C. elegans nematodes while keeping the study object within a confined region, e.g. the field of view of a microscope. Furthermore polyacrylamide gels can easily be combined with PDMS and microfluidics to continuously supply fresh nutrients and remove waste products. Beyond this rather technical work, we set out to chart the influence of spatial structure and dispersal on evolutionary dynamics. To our surprise we found that already one of the most basic experiments imaginable, mixing two genetically identical bacterial populations labeled with distinct fluorescent markers, yielded drastically altered population dynamics in spatial habitats compared to well-mixed conditions. Motile populations in spatial habitats are found to spontaneously segregate over a broad range of initial conditions. We were able to identify dispersal rate as a key determinate of spatial confinement.