title: Bacterial degradation of cyanide and its metal complexes under alkaline conditions.
abstract: A bacterial strain able to use cyanide as the sole nitrogen source under alkaline conditions has been isolated. The bacterium was classified as Pseudomonas pseudoalcaligenes by comparison of its 16S RNA gene sequence to those of existing strains and deposited in the Coleccion Espanola de Cultivos Tipo (Spanish Type Culture Collection) as strain CECT5344. Cyanide consumption is an assimilative process, since (i) bacterial growth was concomitant and proportional to cyanide degradation and (ii) the bacterium stoichiometrically converted cyanide into ammonium in the presence of l-methionine-d,l-sulfoximine, a glutamine synthetase inhibitor. The bacterium was able to grow in alkaline media, up to an initial pH of 11.5, and tolerated free cyanide in concentrations of up to 30 mM, which makes it a good candidate for the biological treatment of cyanide-contaminated residues. Both acetate and d,l-malate were suitable carbon sources for cyanotrophic growth, but no growth was detected in media with cyanide as the sole carbon source. In addition to cyanide, P. pseudoalcaligenes CECT5344 used other nitrogen sources, namely ammonium, nitrate, cyanate, cyanoacetamide, nitroferricyanide (nitroprusside), and a variety of cyanide-metal complexes. Cyanide and ammonium were assimilated simultaneously, whereas cyanide strongly inhibited nitrate and nitrite assimilation. Cyanase activity was induced during growth with cyanide or cyanate, but not with ammonium or nitrate as the nitrogen source. This result suggests that cyanate could be an intermediate in the cyanide degradation pathway, but alternative routes cannot be excluded.
authors.affiliation: Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Veterinaria, Universidad de Extremadura, Avenida de la Universidad SN, E-10071 Cáceres, Spain.
authors.forename: Víctor M
authors.initials: VM
authors.lastname: Luque-Almagro
authors.forename: María-J
authors.initials: MJ
authors.lastname: Huertas
authors.forename: Manuel
authors.initials: M
authors.lastname: Martínez-Luque
authors.forename: Conrado
authors.initials: C
authors.lastname: Moreno-Vivián
authors.forename: M Dolores
authors.initials: MD
authors.lastname: Roldán
authors.forename: L Jesús
authors.initials: LJ
authors.lastname: García-Gil
authors.forename: Francisco
authors.initials: F
authors.lastname: Castillo
authors.forename: Rafael
authors.initials: R
authors.lastname: Blasco
mesh_terms: D000085:Acetates / Q000378:metabolism; D001673:Biodegradation, Environmental; D003470:Culture Media; D003486:Cyanides / Q000737:chemistry / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000032:analysis; D015964:Gene Expression Regulation, Bacterial; D020459:Genes, rRNA; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D044205:Pseudomonas pseudoalcaligenes / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D000085:Acetates; D003470:Culture Media; D003486:Cyanides; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S