The clock-and-wavefront mechanism generates intrinsically scalable patterns for bacterial biofilm development.

Jian-geng Chiou^1,2*, Todd Kwang-Tao Chou², Jordi Garcia-Ojalvo³, Gürol M. Süel²

¹Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
²Department of Molecular Biology, University of California San Diego, La Jolla, CA, USA
³Department of Medicine and Life Sciences, Universitat Pompeu Fabra, Barcelona, Spain

* Presenter:Jian-geng Chiou, email:jchiou@gate.sinica.edu.tw

Patterning of gene expression is a shared feature during the development of a wide range of multicellular systems. While animal embryos deploy well-controlled developmental programs, bacterial biofilms can grow in diverse habitats into undetermined sizes. How developmental patterning retains robustness while system sizes vary remains an open question. Here we show that a segmentation clock robustly patterns nitrogen stress response into concentric rings in Bacillus subtilis biofilms, leading to patterned sporulation. The underlying mechanism is a clock-and-wavefront mechanism driven by a cell-autonomous molecular oscillator built into their nitrogen stress response. We show that such a developmental pattern is robust in contrasting growth contexts where biofilm sizes can differ by 4-fold. We further demonstrated that the clock-and-wavefront mechanism scales the pattern with the biofilm growth rate. Scaling arises from the intrinsic coupling of segmentation patterns with the wavefront speed and, correspondingly, biofilm growth rate and biofilm size. Consequently, bacterial biofilms robustly allocate a proportion of the community to sporulation under diverse conditions without knowledge of a predetermined size.

Keywords: Clock-and-wavefront, Bacteria, Bioflim, Scaling, Pattern Formation