US EPA

2347602 

Journal Article 

Co-regulated genes link sulfide:quinone oxidoreductase and arsenic metabolism in Synechocystis sp. strain PCC6803 

Nagy, CI; Vass, I; Rákhely, G; Vass, IZ; Tóth, A; Duzs, Á; Peca, L; Kruk, J; Kós, PB 

2014 

Yes 

Journal of Bacteriology
ISSN: 0021-9193
EISSN: 1098-5530 

196 

19 

3430-3440 

English 

25022856 

10.1128/JB.01864-14 

WOS:000341237500008 

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. PCC6803 the two metabolic pathways are linked by co-regulated genes that are involved in arsenic transport and sulfide oxidation, and probably in sulfide based alternative photosynthesis. Although Synechocystis sp. 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 arsenite importer at permissive concentrations. We propose that the proteins encoded in the suoRSCT operon might have played an important role under anaerobic, reducing conditions on primordial Earth and it was acquired by the cyanobacterium via horizontal gene transfer.