Sulfur–nitrogen–carbon removal of Pseudomonas sp. C27 under sulfide stress

• Proteomic analysis was made on Pseudomonas sp. C27 under DSR environment.
• Key enzymes for nitrogen metabolism for C27 were identified.
• Key enzymes for carbon metabolism for C27 were identified.
• Key enzymes for sulfide metabolism for C27 were identified.
• Sulfide stress up-regulated key enzymes of C27 for DSR reactions.

Pseudomonas sp. C27 is a facultative autotrophic bacterium that can effectively conduct mixotrophic and heterotrophic denitrification reactions using organic matters and sulfide as electron donors. There is no experimental confirmation on proteomic levels the pure C27 strain can have the capability to simultaneous removal of sulfide, nitrate and organic carbon from waters. The proteome in total C27 cell extracts was observed by two-dimensional gel electrophoresis. The 160 mg/L sulfide up-regulated or specifically expressed succinate dehydrogenase, iron–sulfur protein, oxidoreductase, serine hydroxymethyltransferase, and iron superoxide dismutase for sulfide metabolism, 2-oxoglutarate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, NAD+-dependent aldehyde dehydrogenase, malate dehydrogenase and succinate dehydrogenase for carbon metabolism, and nitrous-oxide reductase and respiratory nitrate reductase for nitrogen metabolism. The study confirmed that the C27 strain has an effective enzyme system to conduct denitrifying sulfide removal reactions. Also, sulfide stress can enhance energy consumption rate and rates of nitrate reduction and sulfide oxidation by C27. Conversely, sulfide stress repressed the sulfate-reducing power of C27, evidenced by down-regulation or specific un-expression of sulfate ABC transporter, periplasmic sulfate-binding protein in the (C + N + S) sample.

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