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BP: Fachverband Biologische Physik

BP 7: Posters: Statistical Physics in Biological Systems

BP 7.24: Poster

Monday, March 14, 2011, 17:15–20:00, P3

Microbial Stain Effect — •Christopher J. Seedig and Oskar Hallatschek — Biophysics & Evolutionary Dynamics Group, MPI for Dynamics and Self Organization, Göttingen, Germany

Droplets of colloidal suspensions leave annular patterns after drying on solid surfaces [1]. This phenomenon is commonly observed in coffee stains, therefore the underlying effect has been termed coffee stain effect. If the suspended colloids have two different sizes, the coffee stains consist of separate rings: smaller beads end up further away from the droplet centre [2]. Here, we study the coffee stain effect using droplets of yeast suspensions on agar plates. These suspensions are mixtures of large and small cells, which can be distinguished by their fluorescent color. We find that, due to the initial positional head start, the small cells enjoy a significant advantage during the colony formation. As a consequence, the small cells occupy a disproportionally large fraction of the final colony. We quantify this "selection advantage" as a function of important control parameters, such as cell size difference or cell density. We argue that the microbial stain effect may play an important role in molecular biology, as it occurs on a daily basis in most modern bio-labs.

[1] Deegan et al., Nature (London), 389, 827-29 (1997)

[2] Byung Mook Weon, Jung Ho Je, Phys Rev E, 82, 015305(R) (2010)