Many different bacterial species form macroscopic clusters when grown in high-salinity media. This suggests that bacteria can easily come together to form multicellular aggregates, which is considered to be the first step in the evolution of more complex multicellular life cycles.
Adapted from Chavhan, Y., Dey, S. & Lind, P.A. Bacteria evolve macroscopic multicellularity by the genetic assimilation of phenotypically plastic cell clustering. Nat Commun 14, 3555 (2023). https://doi.org/10.1038/s41467-023-39320-9 . http://creativecommons.org/licenses/by/4.0/.
Using experimental evolution with E. coli in media with decreasing concentrations of NaCl we showed that the phenotypically plastic macroscopic clustering can be genetically assimilated. This means that the multicellular phenotype is also expressed in low salt environments and is no longer dependent on an environmental signal. We also discovered that mutations in genes involved in peptidoglycan synthesis were responsible for the genetic assimilation. High salinity causes a round cell shape in the ancestor but surprisingly lead to an elongated cell shape in mutants that have genetically assimilated the multicellular phenotype.
Adapted from Chavhan, Y., Dey, S. & Lind, P.A. Bacteria evolve macroscopic multicellularity by the genetic assimilation of phenotypically plastic cell clustering. Nat Commun 14, 3555 (2023). https://doi.org/10.1038/s41467-023-39320-9 . http://creativecommons.org/licenses/by/4.0/.
The Lind Lab at Umeå University 