Collapse of genetic division of labour and evolution of autonomy in pellicle biofilms


Closely related microorganisms often cooperate, but the prevalence and stability of cooperation between different genotypes remain debatable. Here, we track the evolution of pellicle biofilms formed through genetic division of labour and ask whether partially deficient partners can evolve autonomy. Pellicles of Bacillus subtilis rely on an extracellular matrix composed of exopolysaccharide (EPS) and the fibre protein TasA. In monocultures, ∆eps and ∆tasA mutants fail to form pellicles, but, facilitated by cooperation, they succeed in co-culture. Interestingly, cooperation collapses on an evolutionary timescale and ∆tasA gradually outcompetes its partner ∆eps. Pellicle formation can evolve independently from division of labour in ∆eps and ∆tasA monocultures, by selection acting on the residual matrix component, TasA or EPS, respectively. Using a set of interdisciplinary tools, we unravel that the TasA producer (∆eps) evolves via an unconventional but reproducible substitution in TasA that modulates the biochemical properties of the protein. Conversely, the EPS producer (ΔtasA) undergoes genetically variable adaptations, all leading to enhanced EPS secretion and biofilms with different biomechanical properties. Finally, we revisit the collapse of division of labour between Δeps and ΔtasA in light of a strong frequency versus exploitability trade-off that manifested in the solitarily evolving partners. We propose that such trade-off differences may represent an additional barrier to evolution of division of labour between genetically distinct microorganisms.

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Fig. 1: Changes in pellicle productivity and morphology during evolution.
Fig. 2: Complementation assay to recreate the evolved Δeps phenotype.
Fig. 3: Fibre formation by native ΔSP-TasA and its cysteine-containing derivatives.
Fig. 4: Investigation and recreation of the evolved ΔtasA phenotype.
Fig. 5: Population structure and fitness of the evolved Δeps and ΔtasA populations.
Fig. 6: Effects of Δeps or ΔtasA evolutionary advantage on the productivity of mixed pellicles.

Data availability

All data sets generated and analysed during this study are available from the corresponding author on request.

Change history

  • 11 January 2019

    In the version of this Article originally published, author Carolina Falcón Garcia’s name was coded wrongly, resulting in it being incorrect when exported to citation databases. This has now been corrected, though no visible changes will be apparent.


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We thank S. West for his comments on our manuscript. This work was funded by the Deutsche Forschungsgemeinschaft (DFG) to Á.T.K. (KO4741/2.1) within the Priority Program SPP1617. A.D. and C.F.G. were supported by fellowships from the Alexander von Humboldt Foundation and Consejo Nacional de Ciencia y Tecnología (CONACyT), respectively. The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 713683 (COFUNDfellowsDTU). This work was also supported by the DFG through project B11 in the framework of SFB863 granted to O.L., and a start-up grant from the Technical University of Denmark to Á.T.K.

Author information

A.D. and Á.T.K. conceived the project. A.D., M.M., C.F.G., L.K., P.P. and T.H. performed the experiments. B.B. performed the next-generation sequencing data analysis. G.M., G.B., D.L. and O.L. contributed with the methods, analysed the data and supervised the experiments. A.D. and Á.T.K. wrote the manuscript, with all authors contributing to the final version.

Correspondence to Ákos T. Kovács.

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Supplementary information

Supplementary Information

Supplementary Tables 1–5, Supplementary References, Supplementary Figures 1–11, Supplementary Results.

Reporting Summary

Supplementary Dataset 1

List of mutations detected in evolved single isolates and populations.

Supplementary Video 1

Effects of cysteine-containing TasA on wetting behaviour of B. subtilis pellicles.

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Dragoš, A., Martin, M., Falcón García , C. et al. Collapse of genetic division of labour and evolution of autonomy in pellicle biofilms. Nat Microbiol 3, 1451–1460 (2018).

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