title: Pseudomonas pseudoalcaligenes CECT5344, a cyanide-degrading bacterium with by-product (polyhydroxyalkanoates) formation capacity.
abstract: BACKGROUND
  Cyanide is one of the most toxic chemicals produced by anthropogenic activities like mining and jewelry industries, which generate wastewater residues with high concentrations of this compound. Pseudomonas pseudoalcaligenes CECT5344 is a model microorganism to be used in detoxification of industrial wastewaters containing not only free cyanide (CN(-)) but also cyano-derivatives, such as cyanate, nitriles and metal-cyanide complexes. Previous in silico analyses suggested the existence of genes putatively involved in metabolism of short chain length (scl-) and medium chain length (mcl-) polyhydroxyalkanoates (PHAs) located in three different clusters in the genome of this bacterium. PHAs are polyesters considered as an alternative of petroleum-based plastics. Strategies to optimize the bioremediation process in terms of reducing the cost of the production medium are required.
  
  
  RESULTS
  In this work, a biological treatment of the jewelry industry cyanide-rich wastewater coupled to PHAs production as by-product has been considered. The functionality of the pha genes from P. pseudoalcaligenes CECT5344 has been demonstrated. Mutant strains defective in each proposed PHA synthases coding genes (Mpha(-), deleted in putative mcl-PHA synthases; Spha(-), deleted in the putative scl-PHA synthase) were generated. The accumulation and monomer composition of scl- or mcl-PHAs in wild type and mutant strains were confirmed by gas chromatography-mass spectrometry (GC-MS). The production of PHAs as by-product while degrading cyanide from the jewelry industry wastewater was analyzed in batch reactor in each strain. The wild type and the mutant strains grew at similar rates when using octanoate as the carbon source and cyanide as the sole nitrogen source. When cyanide was depleted from the medium, both scl-PHAs and mcl-PHAs were detected in the wild-type strain, whereas scl-PHAs or mcl-PHAs were accumulated in Mpha(-) and Spha(-), respectively. The scl-PHAs were identified as homopolymers of 3-hydroxybutyrate and the mcl-PHAs were composed of 3-hydroxyoctanoate and 3-hydroxyhexanoate monomers.
  
  
  CONCLUSIONS
  These results demonstrated, as proof of concept, that talented strains such as P. pseudoalcaligenes might be applied in bioremediation of industrial residues containing cyanide, while concomitantly generate by-products like polyhydroxyalkanoates. A customized optimization of the target bioremediation process is required to gain benefits of this type of approaches.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Campus de Rabanales, Edificio Severo Ochoa, 1ª Planta Universidad de Córdoba, Córdoba, 14071, Spain. b72macoi@uco.es.
authors.forename: Isabel
authors.initials: I
authors.lastname: Manso Cobos
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Campus de Rabanales, Edificio Severo Ochoa, 1ª Planta Universidad de Córdoba, Córdoba, 14071, Spain. b32ibgam@uco.es.
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Ibáñez García
authors.affiliation: Departamento de Biología Medioambiental, Centro de Investigaciones Biológicas (CIB-CSIC), Madrid, Spain. fepemore@hotmail.com.
authors.forename: Fernando
authors.initials: F
authors.lastname: de la Peña Moreno
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Campus de Rabanales, Edificio Severo Ochoa, 1ª Planta Universidad de Córdoba, Córdoba, 14071, Spain. bb2samel@uco.es.
authors.forename: Lara Paloma
authors.initials: LP
authors.lastname: Sáez Melero
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Campus de Rabanales, Edificio Severo Ochoa, 1ª Planta Universidad de Córdoba, Córdoba, 14071, Spain. b42lualv@uco.es.
authors.forename: Víctor Manuel
authors.initials: VM
authors.lastname: Luque-Almagro
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Campus de Rabanales, Edificio Severo Ochoa, 1ª Planta Universidad de Córdoba, Córdoba, 14071, Spain. biocastillo2@gmail.com.
authors.forename: Francisco
authors.initials: F
authors.lastname: Castillo Rodríguez
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Campus de Rabanales, Edificio Severo Ochoa, 1ª Planta Universidad de Córdoba, Córdoba, 14071, Spain. bb2rorum@uco.es.
authors.forename: María Dolores
authors.initials: MD
authors.lastname: Roldán Ruiz
authors.affiliation: Departamento de Biología Medioambiental, Centro de Investigaciones Biológicas (CIB-CSIC), Madrid, Spain. auxi@cib.csic.es.
authors.forename: María Auxiliadora
authors.initials: MA
authors.lastname: Prieto Jiménez
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Campus de Rabanales, Edificio Severo Ochoa, 1ª Planta Universidad de Córdoba, Córdoba, 14071, Spain. bb1movic@uco.es.
authors.forename: Conrado
authors.initials: C
authors.lastname: Moreno Vivián
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D003486:Cyanides; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis / Q000378:metabolism*; D011549:Pseudomonas / Q000378:metabolism*; D044205:Pseudomonas pseudoalcaligenes / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003486:Cyanides; D054813:Polyhydroxyalkanoates