Jens Appel
Cyanobacteria and Hydrogen Metabolism
The main focus of my group is on cyanobacteria and their hydrogen metabolism. Cyanobacteria are photoautotrophic organisms able to live just by using sunlight, water and some minerals to build up all their cellular components. Their live style is often compared to plants and in fact there is no doubt that a cyanobacterium has been the ancestor of the green organelles, the chloroplasts of the plant cells. In addition to the photosynthetic apparatus cyanobacteria also contain enzymes that are able to produce or consume hydrogen and therefore, are attractive candidates for the production of this environmentally friendly energy source.
Our goal is to understand the basic principles of the enzymes, their regulation and biochemistry and the metabolic pathways involved to thoughtfully manipulate the cell machinery to increase the output of hydrogen.
In parallel investigations we are also working on the NDH–1 complex of cyanobacteria. This complex is involved in many important electron transfer pathways like respiration, cyclic electron transport and the CCM (carbon concentrating mechanism). It is also tightly intertwined with H2 metabolism as seen in mutants impaired in NDH–1 function. Beneath these mutants are those with the highest hydrogen output found until now.
Selected Publications
Gutthann F., Egert M., Marques A., Appel J. (2007) Inhibition of respiration and nitrate assimilation enhances hydrogen evolution in Synechocystis sp. PCC 6803. Biochem. Biophys. Acta–Bioenergetics 1767: 161–169
Hoffmann D., Gutekunst K., Klissenbauer M., Schulz–Friedrich R., Appel J. (2006) Mutagenesis of hydrogenase accessory genes of Synechocystis sp. PCC 6803 – additional homologs of hypA and hypB are not active in hydrogenase maturation. FEBS Journal 273: 4516–4527.
Ludwig M., Schulz–Friedrich R., Appel J. (2006) Occurrence of hydrogenases in cyanobacteria and anoxygenic photosynthetic bacteria: implications for the phylogenetic origin of cyanobacterial and algal hydrogenases. J. Mol. Evol. 63: 758–768.
Gutekunst K., Hoffmann D., Lommer M., Egert M., Schulz–Friedrich R., Appel J. (2006) Metal dependence and intracellular regulation of the bidirectional NiFe–hydrogenase in Synechocystis sp. PCC 6803. Int. J. Hydr. Energ. 31: 1452–1459.
Gutekunst K., Phunpruch S., Schwarz S., Schuchardt S., Schulz–Friedrich R., Appel J. (2005) LexA regulates the bidirectional hydrogenase in the cyanobacterium Synechocystis sp. PCC 6803 as a transcription activator. Mol. Microbiol. 58: 810–823.
Zhang P., Battchikova N., Jansen T., Appel J., Ogawa T. and Aro E.M. (2004) Expression and functional roles of the two distinct NDH–1 complexes and the carbon acquisition complex NdhD3/NdhF3/CupA/Sll1735 in Synechocystis sp. PCC 6803. Plant Cell 16: 3326–3340.
Appel J., Phunpruch S., Steinmüller K., Schulz R. (2000) The bidirectional hydrogenase of Synechocystis sp. PCC 6803 works as an electron valve during photosynthesis. Arch. Microbiol. 173: 333–338.
Appel J., Schulz R. (1998) Hydrogen metabolism in organisms with oxygenic photosynthesis – hydrogenases as important regulatory devices for a proper redox poising? J. Photochem. Photobiol. B: Biol. 47: 1–11.