Our goal is to reduce H₂S in oil wastewater using Sulfide-Quinone Reductase in genetically modified Synechococcus elongatus PCC 7942 and use products of the reaction to produce hydrogen and utilize sulfur-rich biomass in the production of the catalytically active material.

Synechococcus elongatus PCC 7942

Synechococcus elongatus PCC 7942 is a freshwater obligate photoautotroph [6]. Was first reliably transformed cyanobacterium [6]. One of the most studied cyanobacteria and used as a model organism with well-investigated chromosome and plasmids sequences [6].

PHOTOSYNTHESIS

Being an essential part of an organism’s metabolism photosynthetic pathways in S. elongatus is the main subject of modification. D1 protein of Photosystem II acts as reaction center in the splitting of water and this is the main target to reach inhibition of PS II [5]. There is a natural inhibition of PSII in the minimal concentration of H₂S (60 uM)[1].

SULFIDE-QUINONE REDUCTASE

SQR catalyzes sulfide-dependent plastoquinone reduction in anaerobic conditions. In our project, SQR originates from organism Leptolyngbya hensonii cyanobacteria that can live in sulfidic conditions and change metabolism back to oxygenic photosynthesis accordingly to conditions [2], [3], [4]. To force cyanobacteria to use SQR, Photosystem II will be inhibited by H₂S and psbA1 gene. Produced sulfur will be in the form of polysulfide and remain in the cell.

References:

1. 1. Cohen, Y., Jørgensen, B.B., Revsbech, N.P. and Poplawski, R., 1986. Adaptation to hydrogen sulfide of oxygenic and anoxygenic photosynthesis among cyanobacteria. Applied and Environmental Microbiology, 51(2), pp.398-407.
2. 2. Encyclopedia of Life. (n.d.). Geitlerinema splendidum - Overview - Encyclopedia of Life. [online] Available at: http://eol.org/pages/919054/overview [Accessed 15 Sep. 2018].
3. 3. Hamilton, T.L., Klatt, J.M., De Beer, D. and Macalady, J.L., 2018. Cyanobacterial photosynthesis under sulfidic conditions: insights from the isolate Leptolyngbya sp. strain hensonii. The ISME journal, 12(2), p.568.
4. 4. Strunecky, O., Bohunicka, M., Johansen, J., Capkova, K., Raabova, L., Dvorak, P. and Komarek, J. (2017). A revision of the genus Geitlerinema and a description of the genus Anagnostidinema gen. nov. (Oscillatoriophycidae, Cyanobacteria). Fottea, 17(1), pp.114-126.
5. 5. Uniprot.org. (n.d.). psbA - Photosystem II protein D1 precursor - Arabidopsis thaliana (Mouse-ear cress) - psbA gene & protein. [online] Available at: https://www.uniprot.org/uniprot/P83755 [Accessed 15 Sep. 2018].
6. 6. Uniprot.org. (n.d.). Synechococcus elongatus (strain PCC 7942) (Anacystis nidulans R2). [online] Available at: https://www.uniprot.org/proteomes/UP000002717 [Accessed 15 Sep. 2018].