title: Coregulated genes link sulfide:quinone oxidoreductase and arsenic metabolism in Synechocystis sp. strain PCC6803.
abstract: Although the biogeochemistry of the two environmentally hazardous compounds arsenic and sulfide has been extensively investigated, the biological interference of these two toxic but potentially energy-rich compounds has only been hypothesized and indirectly proven. Here we provide direct evidence for the first time that in the photosynthetic model organism Synechocystis sp. strain PCC6803 the two metabolic pathways are linked by coregulated genes that are involved in arsenic transport, sulfide oxidation, and probably in sulfide-based alternative photosynthesis. Although Synechocystis sp. strain PCC6803 is an obligate photoautotrophic cyanobacterium that grows via oxygenic photosynthesis, we discovered that specific genes are activated in the presence of sulfide or arsenite to exploit the energy potentials of these chemicals. These genes form an operon that we termed suoRSCT, located on a transposable element of type IS4 on the plasmid pSYSM of the cyanobacterium. suoS (sll5036) encodes a light-dependent, type I sulfide:quinone oxidoreductase. The suoR (sll5035) gene downstream of suoS encodes a regulatory protein that belongs to the ArsR-type repressors that are normally involved in arsenic resistance. We found that this repressor has dual specificity, resulting in 200-fold induction of the operon upon either arsenite or sulfide exposure. The suoT gene encodes a transmembrane protein similar to chromate transporters but in fact functioning as an arsenite importer at permissive concentrations. We propose that the proteins encoded by the suoRSCT operon might have played an important role under anaerobic, reducing conditions on primordial Earth and that the operon was acquired by the cyanobacterium via horizontal gene transfer.
authors.affiliation: Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary.
authors.forename: Csaba I
authors.initials: CI
authors.lastname: Nagy
authors.affiliation: Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary.
authors.forename: Imre
authors.initials: I
authors.lastname: Vass
authors.affiliation: Department of Biotechnology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Rákhely
authors.affiliation: Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary.
authors.forename: István Zoltán
authors.initials: IZ
authors.lastname: Vass
authors.affiliation: Department of Biotechnology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary.
authors.forename: András
authors.initials: A
authors.lastname: Tóth
authors.affiliation: Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary.
authors.forename: Agnes
authors.initials: A
authors.lastname: Duzs
authors.affiliation: Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary.
authors.forename: Loredana
authors.initials: L
authors.lastname: Peca
authors.affiliation: Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Kruk
authors.affiliation: Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary Department of Biotechnology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary kp@brc.hu.
authors.forename: Péter B
authors.identifier: http://orcid.org/0000-0001-7443-9671
authors.initials: PB
authors.lastname: Kós
mesh_terms: D001151:Arsenic / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D011808:Quinone Reductases / Q000235:genetics* / Q000378:metabolism; D011809:Quinones / Q000378:metabolism; D013440:Sulfides / Q000378:metabolism; D046939:Synechocystis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D011809:Quinones; D013440:Sulfides; D011808:Quinone Reductases; C073412:sulfide quinone reductase; D001151:Arsenic