Assembling the chlorophyll biosynthetic pathway into E. coli

Green E.Coli large

In new work published in the journal Science Advances researchers at the University of Sheffield have assembled the complete biosynthetic pathway for chlorophyll into E. coli for the first time, a major landmark on the road to engineering photosynthesis into a heterotrophic organism.

Chlorophylls are essential cofactors for photosynthesis, which sustains global food chains and oxygen production. Billions of tons of chlorophylls are synthesized annually, yet full understanding of chlorophyll biosynthesis had been hindered by the lack of characterization of the Magnesium protoporphyrin IX monomethyl ester oxidative cyclase step, which confers the distinctive green color of these pigments.

The new research led by Professor Neil Hunter FRS from the Department of Molecular Biology and Biotechnology, together with collaborators at Pennsylvania State University, demonstrates that armed with the knowledge of the cyclase reaction, published last year in the Proceedings of the National Academy of Sciences USA, it is now possible to create a genetic module that encodes the complete chlorophyll biosynthetic pathway and show that it functions in Escherichia coli. The genetic module encodes 12 genes that convert the endogenous protoporphyrin IX, a precursor of the molecule haem, in E. coli into chlorophyll a, turning the cells green.

Professor Hunter commented “This exciting new work conforms to Richard Feynman’s idea of 'What I cannot create, I do not understand'. Our results delineate a minimum set of enzymes required to make chlorophyll, and now we can transplant that ability into another organism of choice”

The full paper, Complete enzyme set for chlorophyll biosynthesis in Escherichia coli, is available from the Science Advances website.