title: Involvement of Pseudomonas aeruginosa rhodanese in protection from cyanide toxicity.
abstract: Cyanide is a serious environmental pollutant and a biocontrol metabolite in plant growth-promoting Pseudomonas species. Here we report on the presence of multiple sulfurtransferases in the cyanogenic bacterium Pseudomonas aeruginosa PAO1 and investigate in detail RhdA, a thiosulfate:cyanide sulfurtransferase (rhodanese) which converts cyanide to less toxic thiocyanate. RhdA is a cytoplasmic enzyme acting as the principal rhodanese in P. aeruginosa. The rhdA gene forms a transcriptional unit with the PA4955 and psd genes and is controlled by two promoters located upstream of PA4955 and rhdA. Both promoters direct constitutive RhdA expression and show similar patterns of activity, involving moderate down-regulation at the stationary phase or in the presence of exogenous cyanide. We previously observed that RhdA overproduction protects Escherichia coli against cyanide toxicity, and here we show that physiological RhdA levels contribute to P. aeruginosa survival under cyanogenic conditions. The growth of a DeltarhdA mutant is impaired under cyanogenic conditions and fully restored upon complementation with rhdA. Wild-type P. aeruginosa outcompetes the DeltarhdA mutant in cyanogenic coculture assays. Hence, RhdA could be regarded as an effector of P. aeruginosa intrinsic resistance to cyanide, insofar as it provides the bacterium with a defense mechanism against endogenous cyanide toxicity, in addition to cyanide-resistant respiration.
authors.affiliation: Dipartimento di Biologia, Università Roma Tre, Viale G. Marconi 446, 00146 Rome, Italy.
authors.forename: Rita
authors.initials: R
authors.lastname: Cipollone
authors.forename: Emanuela
authors.initials: E
authors.lastname: Frangipani
authors.forename: Federica
authors.initials: F
authors.lastname: Tiburzi
authors.forename: Francesco
authors.initials: F
authors.lastname: Imperi
authors.forename: Paolo
authors.initials: P
authors.lastname: Ascenzi
authors.forename: Paolo
authors.initials: P
authors.lastname: Visca
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D003470:Culture Media; D003486:Cyanides / Q000378:metabolism / Q000633:toxicity*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D013861:Thiocyanates / Q000378:metabolism; D013884:Thiosulfate Sulfurtransferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D003486:Cyanides; D013861:Thiocyanates; D013884:Thiosulfate Sulfurtransferase