Genetic manipulation of structural color in bacterial colonies

Villads Egede Johansen; Laura Catón; Raditijo Hamidjaja; Els Oosterink; Bodo D. Wilts; Torben Sølbeck Rasmussen; Michael Mario Sherlock; Colin J. Ingham; Silvia Vignolini

doi:10.1073/pnas.1716214115

New Research In

Edited by David A. Weitz, Harvard University, Cambridge, MA, and approved January 17, 2018 (received for review September 25, 2017)

Significance

We demonstrate the genetic modification of structural color in a living system by using bacteria Iridescent 1 (IR1) as a model system. IR1 colonies consist of rod-shaped bacteria that pack in a dense hexagonal arrangement through gliding and growth, thus interfering with light to give a bright, green, and glittering appearance. By generating IR1 mutants and mapping their optical properties, we show that genetic alterations can change colony organization and thus their visual appearance. The findings provide insight into the genes controlling structural color, which is important for evolutionary studies and for understanding biological formation at the nanoscale. At the same time, it is an important step toward directed engineering of photonic systems from living organisms.

Abstract

Naturally occurring photonic structures are responsible for the bright and vivid coloration in a large variety of living organisms. Despite efforts to understand their biological functions, development, and complex optical response, little is known of the underlying genes involved in the development of these nanostructures in any domain of life. Here, we used Flavobacterium colonies as a model system to demonstrate that genes responsible for gliding motility, cell shape, the stringent response, and tRNA modification contribute to the optical appearance of the colony. By structural and optical analysis, we obtained a detailed correlation of how genetic modifications alter structural color in bacterial colonies. Understanding of genotype and phenotype relations in this system opens the way to genetic engineering of on-demand living optical materials, for use as paints and living sensors.

Footnotes

↵¹V.E.J. and L.C. contributed equally to this work.
↵²To whom correspondence may be addressed. Email: sv319{at}cam.ac.uk or colinutrecht{at}gmail.com.

Author contributions: V.E.J., L.C., C.J.I., and S.V. designed research; V.E.J., L.C., R.H., E.O., B.D.W., T.S.R., M.M.S., C.J.I., and S.V. performed research; V.E.J., L.C., R.H., E.O., B.D.W., T.S.R., M.M.S., C.J.I., and S.V. analyzed data; V.E.J., L.C., C.J.I., and S.V. wrote the paper; V.E.J. planned experiments, cultivated bacteria, performed goniometry and SEM, and processed and analyzed optical/SEM data; L.C. planned and executed genetics and genomics and contributed to conclusions and writing; R.H. cultivated bacteria and performed experiments related to volatiles; B.D.W. performed optical analysis and SEM; E.O. isolated and characterized IR1; T.S.R. cultivated bacteria, fixed samples, and processed SEM images; M.M.S. cultivated bacteria and performed goniometry and subsequent analysis; S.V. performed data processing and analysis; C.J.I. performed transposon mutagenesis, fixation for SEM, SEM, genetic analysis, experimental design, and data analysis; V.E.J., L.C., C.J.I., and S.V. led the writing of the paper; and V.E.J., L.C., R.H., E.O., B.D.W., T.S.R., M.M.S., C.J.I., and S.V. discussed results and commented on the manuscript.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. NQOT00000000). Additional data related to this publication are available at the University of Cambridge data repository (doi.org/10.17863/CAM.16794).
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1716214115/-/DCSupplemental.

Published under the PNAS license.

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