Photo Credit: Devaki Bhaya. Overlay: Rosanna Chau and Tristan Ursell
The recently published article “Motility Enhancement through Surface Modification Is Sufficient for Cyanobacterial Community Organization during Phototaxis.” by Ursell et al. was featured on the cover of the September issue of PLoS Comput Biol. The research represents an ongoing collaboration between the groups of Devaki Bhaya, at the Carnegie Institution and Dr. K.C. Huang, Department of Bioengineering, Stanford. Dr. Bhaya has extensively studied the behavior of the model photosynthetic cyanobacterium Synechocystis sp. PCC 6803, which exhibits light-directed motility (“phototaxis”) over surfaces, resulting in the emergence of dynamic, spatially organized multi-cellular communities.
This striking emergent behavior of communities cannot be easily predicted from the behaviors of individual cells. To probe this community behavior, time-lapse video microscopy was coupled with quantitative analysis of single-cell dynamics, under varying light conditions. This led to the development of a biophysical model that matches experimental observations. The model predicts the emergence of community behavior, even in the absence of direct cellular interactions or changes in single-cell behavior, and that cells possibly lay down substances that facilitate this behavior. Further exploration of surface-based communication could provide insight into the behavior of a wide array of biological communities.
Dr. Bhaya comments “This is exciting because it highlights the strength of collaborations across disciplines, which can be challenging but gives us new directions to explore.” Dr. Huang, whose lab develops biophysical models at cellular and community scales, also observed “The origins of collective motility are challenging to uncover, and phototaxis provides an exquisitely sensitive and tunable system from which to reveal general principles." Dr.Tristan Ursell, a post-doc in Bioengineering, Dr. Sussi Wisen, post-doc at the Carnegie Institution and Rosanna Chau, a graduate student co-advised by KC Huang and Devaki Bhaya, all contributed equally to the work. The research was partially funded by the NSF (grants to DB and KC) as well as by a Stanford Bio-X IIP seed grant
The image shows cyanobacterial cells on a moist surface, moving towards a directed light source. This phototactic behavior results in striking and regularly ordered "fingers" of cell groups. We model this behavior as a biased random walk, which, in combination with cell-mediated surface modification, recapitulates many experimentally observed features. By tuning cellular concentration and light intensity, we show that this behavior follows robust scaling laws and only emerges under certain conditions, and may be a general mechanism for cells to change their group behavior in response to external cues. See Ursell et al
http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003205 , republished in accordance with Creative Commons license (CC-BY).