Evolution of cellular decisions reflects the environment

Organisms respond continuously to their environment. How did that process evolve? Researchers from the FOM Institute AMOLF have now shown that a changing environment is enough - a response to these changes then spontaneously evolves within the cell. The researchers publish their groundbreaking results in the prestigious journal Cell today.

Life itself would be impossible without adequate responses to the environment. Cells are continuously interpreting threats and opportunities in the environment and responding to these, for example with a movement or production of a protein. How responses arise in organisms has puzzled evolutionary biologists since the time of Darwin. The underlying interaction between genetic and environmental factors has now been unravelled by AMOLF group leader Professor Sander Tans and his team.

They developed a combination of two new scientific disciplines: synthetic biology and systems biology. This enabled them to control genetic changes in cells by producing a new strain of the E. coli bacterium. Measurements and mathematical models of the system together revealed how changes in the environment give rise to selection pressure, and with that the evolution of the cell's response.

The cells were found to evolve towards the most optimal response by means of random mutations and competition. They developed themselves as a perfect ‘mirror’ of their environment: for each detrimental change in the environment, the evolved cells produced neutralising proteins as a countermovement. As a result of this perfect response, the maximum reproductive rate could be maintained during the variations.

This multidisciplinary research opens up the possibility of making more use of evolutionary biology as a predictive science. Moreover, the highly promising results have yielded many new questions. For example, does this mean that humans are also a perfect mirror of the history of our environment? Does the unpredictability of evolution mainly lie in the uncertain environment or in the organisms as well? And at a more general level, what are the actual limits of evolution? The study has already provided a small glimpse ahead in this respect; although the evolutionary outcome was optimal, the evolutionary pathway nevertheless exhibited flaws. The researchers could trace these flaws back to specific interactions between amino acids in a regulatory protein, which led to rare combinations of several mutations being needed for the adaptation.

Reference
Tradeoffs and optimality in the evolution of gene regulation,
Frank J. Poelwijk, Marjon G. J. de Vos & Sander J. Tans
Cell (2011). DOI:10.1016/j.cell.2011.06.035

Contact
Prof. Sander Tans, s.tansATamolf.nl, +31 6 3195 9067

Fig. 1: Artist’s impression of the prediction of evolution. A bacteria can be seen in the glass ball, which has evolved a different response and is swimming in a different direction than the population from which it originates. (© Tans/deVos/Tremani)

Fig 2: Schematic illustration of the research. The bacteria grow and divide in a variable environment: initially the internal response is detrimental and few cells survive. As a result of mutation and selection, the response changes (a red response in a green environment) and the population grows rapidly. On the right, the changes in fitness can be seen: first of all a rapid improvement, then a slowing down due to a genetic limitation, and finally evolution towards the optimum.