||Bacteria Escherichia coli
||Claassens NJ, Volpers M, dos Santos VA, van der Oost J, de Vos WM. Potential of proton-pumping rhodopsins: engineering photosystems into microorganisms. Trends Biotechnol. 2013 Nov31(11):633-42. doi: 10.1016/j.tibtech.2013.08.006. p.639 right column 2nd paragraphPubMed ID24120288
||Kim, J. et al. Improved production of biohydrogen in lightpowered Escherichia coli by co-expression of proteorhodopsin and heterologous hydrogenase. Microb Cell Fact. 2012 Jan 4 11: 2. doi: 10.1186/1475-2859-11-2.PubMed ID22217184
||p.639 right column 2nd paragraph:"In addition to ATP synthesis and transport, the PMF [Proton Motive Force] generated from a PPR photosystem may also boost other biotechnologically relevant pathways. As an example, when introducing a PPR system together with an oxygen-tolerant hydrogenase in E. coli, the hydrogen production can be increased by 30% in light [primary source]. It is hypothesized that the light-boosted PMF makes more protons available for the hydrogenase."