Nowadays there is a large societal interest in developing production routes for chemicals and fuels which are not dependent on fossil resources. Photosynthetic microorganisms converting (sun)light to products are an interesting option. However, these organisms are often lacking desirable features needed for metabolic engineering to optimize production pathways. So why not introduce a photosystem into an attractive standard production host of biotechnology: Escherichia coli. When E. coli harboring a photosystem can be powered by light, consumption of valuable carbon substrates can be decreased and product yields may improve.
How to develop a phototrophic E. coli?
As E. coli does not harbor a photosystem itself, such system has to be introduced by synthetic biology tools. Relatively simple photosystems are the recently discovered proton-pumping rhodopsins, which are in fact light-driven proton pumps (1). These proton pumps are found in many bacteria and archaea, these pumps formed by a transmembrane protein binding a pigment (retinal) molecule. Expressing this protein in E. coli can generate a proton flux in light, which can be subsequently used to generate ATP via ATPases (2,3). Within this project we want to develop and characterize rhodopsin based phototrophic E. coli strains and integrate this with ATP-consuming production routes. We want to characterize the interactions of light, rhodopsin proton fluxes and the E. coli metabolism and production routes. In addition to E. coli we are investigating the potential of engineering rhodopsins in other interesting hosts.
What techniques can be used?
Techniques which you may use during a thesis project are for example: molecular cloning, growth and production experiments in light, proton pumping assays, enzyme assays, spectroscopic quantification methods and HPLC analyses. Also in silico analyses, by e.g. genome-scale modelling can be included in your thesis project.
Interested in a thesis project?
Thesis projects are available for enthusiastic MSc or BSc students with an interest in synthetic biology, biotechnology, metabolic engineering or microbial physiology. Are you interested in doing a thesis within this project, or do you want to know more? Just contact me by mail: email@example.com, or visit: Dreijenplein 10, WUR building nr 316, room 0.045, or call: +31317483112.
(1) Claassens, N. J., Volpers, M., dos Santos, V. a P. M., van der Oost, J., & de Vos, W. M. (2013). Potential of proton-pumping rhodopsins: engineering photosystems into microorganisms. Trends in Biotechnology, 31(11), 633–42. doi:10.1016/j.tibtech.2013.08.006.
(2) Walter JM, Greenfield D, Bustamante C, Liphardt J: Light-powering Escherichia coli with proteorhodopsin. Proceedings of the National Academy of Sciences 2007, 104:2408-2412.
(3) Martinez A, Bradley AS, Waldbauer JR, Summons RE, DeLong EF: Proteorhodopsin photosystem gene expression enables photophosphorylation in a heterologous host. Proceedings of the National Academy of Sciences of the United States of America 2007, 104:5590-5595.
This project is part of the strategic plan of Wageningen UR about Systems Biology for Food, Feed, and Health. More information about WCSB and the other 13 projects involved can be found at the website www.wur.nl/systemsbiology.