Localized cell death focuses mechanical forces during 3D patterning in a biofilm

Localized cell death focuses mechanical forces during 3D patterning in a biofilm

1. Munehiro Asally^a,
2. Mark Kittisopikul^a,^b,^c,
3. Pau Rué^d,^e,
4. Yingjie Du^f,
5. Zhenxing Hu^f,
6. Tolga Çağatay^b,^c,
7. Andra B. Robinson^b,^c,
8. Hongbing Lu^f,
9. Jordi Garcia-Ojalvo^d,^e, and
10. Gürol M. Süel^a,¹

+ Author Affiliations

1. ^aSection of Molecular Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093;
2. ^bDepartment of Pharmacology and
3. ^cGreen Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390;
4. ^dDepartament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, E-08222 Terrassa, Spain;
5. ^eDepartment of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain; and
6. ^fDepartment of Mechanical Engineering, University of Texas at Dallas, Richardson, TX 75080

1. Edited* by Herbert Levine, University of California at San Diego, La Jolla, CA, and approved August 27, 2012 (received for review July 19, 2012)

Abstract

From microbial biofilm communities to multicellular organisms, 3D macroscopic structures develop through poorly understood interplay between cellular processes and mechanical forces. Investigating wrinkled biofilms of Bacillus subtilis, we discovered a pattern of localized cell death that spatially focuses mechanical forces, and thereby initiates wrinkle formation. Deletion of genes implicated in biofilm development, together with mathematical modeling, revealed that ECM production underlies the localization of cell death. Simultaneously with cell death, we quantitatively measured mechanical stiffness and movement in WT and mutant biofilms. Results suggest that localized cell death provides an outlet for lateral compressive forces, thereby promoting vertical mechanical buckling, which subsequently leads to wrinkle formation. Guided by these findings, we were able to generate artificial wrinkle patterns within biofilms. Formation of 3D structures facilitated by cell death may underlie self-organization in other developmental systems, and could enable engineering of macroscopic structures from cell populations.

• pattern formation
• self-assembly
• systems dynamics

Footnotes

• ↵¹To whom correspondence should be addressed. E-mail: gsuel@ucsd.edu.

• Author contributions: M.A., M.K., P.R., J.G.-O., and G.M.S. designed research; M.A., P.R., Y.D., Z.H., and A.B.R. performed research; M.A., M.K., P.R., T.Ç., and J.G.-O. contributed new reagents/analytic tools; M.A., M.K., Y.D., Z.H., H.L., and G.M.S. analyzed data; and M.A., J.G.-O., and G.M.S. wrote the paper.
• The authors declare no conflict of interest.
• ↵*This Direct Submission article had a prearranged editor.
• This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1212429109/-/DCSupplemental.

Freely available online through the PNAS open access option.