A proteome analysis of the tetracyanonickelate (II) responses in Klebsiella oxytoca

Tetracyanonickelate (II) (TCN) has been proved to be degraded by Klebsiella oxytoca. In order to examine the physiological responses of TCN degradation by this bacterium, two-dimensional (2-DE) electrophore-sis approach and Matrix-assisted laser desorption/ionization-time of flight-mass spectrometry allow us to identify 91 proteins spots that were significantly altered in the presence of 1 mM TCN in relative to that in 1 mM ammonia when K. oxytoca grown at the late-log phase. Among them, 43 proteins were successfully identified. Fractions enriched in hydrophobic proteins were obtained with a specific extraction method based on temperature-dependent phase partitioning with Triton X-114, with the successful identification of 26 proteins out of 41 differential proteins. Some proteins were related with TCN metabolism. OsmC-like protein, molecular chaperone DnaK, glu-tathione S-transferase, alkyl hydroperoxide reduc-tase, DNA protection during starvation conditions and DNA binding ferritin-like protein can counteract the oxidative stress from TCN biodegradation. The nitrogenase had been suggested to participate in TCN degradation by K. oxytoca, and was upregulated in TCN-treated cells as expected. The induction of glutamine synthetase could enhance the assimilation of limited nitrogen source produced from the bioconversion of TCN into ammonia as the alternate nitrogen source for bacteria growth. These findings could provide new insights into the inducible mechanisms underlying the capacity of K. oxytoca to tolerate TCN stress.