This Article Full Text (PDF) Other Versions of this Article: AEM.02143-06v1 73/2/390    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cipollone, R. Articles by Visca, P. Search for Related Content PubMed PubMed Citation Articles by Cipollone, R. Articles by Visca, P. Agricola Articles by Cipollone, R. Articles by Visca, P.

 Previous Article  |  Next Article 

Appl. Environ. Microbiol. doi:10.1128/AEM.02143-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Involvement of Pseudomonas aeruginosa rhodanese in protection from cyanide toxicity

Dipartimento di Biologia, Università ‘Roma Tre’, Viale G. Marconi 446, 00146 Rome, Italy; Istituto Nazionale per le Malattie Infettive I.R.C.C.S. ‘Lazzaro Spallanzani’, Via Portuense 292, 00149 Rome, Italy

^* To whom correspondence should be addressed. Email: visca{at}uniroma3.it.

	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 Pseudomomas 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 PA4955 and psd genes, and is controlled by two promoters located upstream of PA4955 and rhdA. Both promoters direct constitutive RhdA expression and show a similar pattern 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 rhdA mutant is impaired under cyanogenic conditions, and fully restored upon complementation with rhdA. Wild type P. aeruginosa outcompetes the rhdA mutant in cyanogenic co-culture assays. Hence, RhdA could be regarded as an effector of P. aeruginosa intrinsic resistance to cyanide, in so far as it provides the bacterium with a defense mechanism against endogenous cyanide toxicity, additional to cyanide-resistant respiration.