Cyanate Assimilation by the Alkaliphilic Cyanide-Degrading Bacterium <i>Pseudomonas pseudoalcaligenes</i> CECT5344: Mutational Analysis of the <i>cyn</i> Gene Cluster

• Main Authors: Lara Paloma Sáez, Purificación Cabello, María Isabel Ibáñez, Víctor Manuel Luque-Almagro, María Dolores Roldán, Conrado Moreno-Vivián
• Format: Article
• Language: English
• Published: MDPI AG 2019-06-01
• Series: International Journal of Molecular Sciences
• Subjects: <i>Pseudomonas pseudoalcaligenes</i>; cyanate; cyanase; cyanide; jewelry residue; nitrate; nitrite
• Online Access: https://www.mdpi.com/1422-0067/20/12/3008

The alkaliphilic bacterium <i>Pseudomonas pseudoalcaligenes</i> CECT5344 can grow with cyanate, cyanide, or cyanide-containing industrial residues as the sole nitrogen source, but the assimilation of cyanide and cyanate takes place through independent pathways. Therefore, cyanide degradation involves a chemical reaction between cyanide and oxaloacetate to form a nitrile that is hydrolyzed to ammonium by the nitrilase NitC, whereas cyanate assimilation requires a cyanase that catalyzes cyanate decomposition to ammonium and carbon dioxide. The <i>P. pseudoalcaligenes</i> CECT5344 <i>cynFABDS</i> gene cluster codes for the putative transcriptional regulator CynF, the ABC-type cyanate transporter CynABD, and the cyanase CynS. In this study, transcriptional analysis revealed that the structural <i>cynABDS</i> genes constitute a single transcriptional unit, which was induced by cyanate and repressed by ammonium. Mutational characterization of the <i>cyn</i> genes indicated that CynF was essential for <i>cynABDS</i> gene expression and that nitrate/nitrite transporters may be involved in cyanate uptake, in addition to the CynABD transport system. Biodegradation of hazardous jewelry wastewater containing high amounts of cyanide and metals was achieved in a batch reactor operating at an alkaline pH after chemical treatment with hydrogen peroxide to oxidize cyanide to cyanate.