Uncoupling effect of nitrite during denitrification by Pseudomonas fluorescens: An in vivo 31P-NMR study

✍ Scribed by Wilbert F. H. Sijbesma; Jonas S. Almeida; Maria A. M. Reis; Helena Santos

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 637 KB
• Volume: 52
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/(sici)1097-0290(19961005)52:1<176::aid-bit18>3.0.co;2-m

✦ Synopsis

In vivo 31P-NMR was used to investigate the basis for the inhibition of denitrification by nitrite accumulated endogenously by Pseudomonas fluorescens ATCC 17822 (biotype II) at pH 7.0. Cells were immobilized in K-carrageenan to obtain high cell concentrations in the NMR tube. Acetate and nitrate in two concentration ratios were supplied as electron donor and acceptor, respectively, to achieve different levels of nitrite accumulation. During denitrification, cells were able to maintain a pH gradient of approximately 0.4 to 0.5 units, but when nitrite accumulation reached values approximating 27 m M the transmembrane ApH collapsed sharply. Nitrite stimulated the reduction rate of nitrate; furthermore, at nitrite concentrations below 1 mM, activation of oxygen respiratory rates was observed in cells grown under aerobic conditions. The results provide evidence for nitrite acting as a protonophore (an uncoupler that increases the proton permeability of membranes by a shuttling mechanism).