DNA microarray analysis of the cyanotroph Pseudomonas pseudoalcaligenes CECT5344 in response to nitrogen starvation, cyanide and a jewelry wastewater

Abstract

tPseudomonas pseudoalcaligenes CECT5344 is an alkaliphilic bacterium that can use cyanide as nitrogensource for growth, becoming a suitable candidate to be applied in biological treatment of cyanide-containing wastewaters. The assessment of the whole genome sequence of the strain CECT5344 hasallowed the generation of DNA microarrays to analyze the response to different nitrogen sources. ThemRNA of P. pseudoalcaligenes CECT5344 cells grown under nitrogen limiting conditions showed consid-erable changes when compared against the transcripts from cells grown with ammonium; up-regulatedgenes were, among others, the glnK gene encoding the nitrogen regulatory protein PII, the two-componentntrBC system involved in global nitrogen regulation, and the ammonium transporter-encoding amtBgene. The protein coding transcripts of P. pseudoalcaligenes CECT5344 cells grown with sodium cyanideor an industrial jewelry wastewater that contains high concentration of cyanide and metals like iron,copper and zinc, were also compared against the transcripts of cells grown with ammonium as nitrogensource. This analysis revealed the induction by cyanide and the cyanide-rich wastewater of four nitrilase-encoding genes, including the nitC gene that is essential for cyanide assimilation, the cyanase cynS geneinvolved in cyanate assimilation, the cioAB genes required for the cyanide-insensitive respiration, andthe ahpC gene coding for an alkyl-hydroperoxide reductase that could be related with iron homeostasisand oxidative stress. The nitC and cynS genes were also induced in cells grown under nitrogen starvationconditions.In cells grown with the jewelry wastewater, a malate quinone:oxidoreductase mqoB gene and severalgenes coding for metal extrusion systems were specifically induced.