Nickel accumulation and storage in Bradyrhizobium japonicum

• Published in: Applied and Environmental Microbiology 1990-06, Vol.56 (6), p.1905-1911
• Main Authors: Maier, R.J. (The Johns Hopkins University, Baltimore, MD), Pihl, T.D, Stults, L, Spray, W
• Format: Article
• Language: English
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; BACTERIA; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BIOLOGICAL ACCUMULATION; Biological and medical sciences; BIOLOGICAL FUNCTIONS; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; Bradyrhizobium japonicum; CITOPLASMA; CYTOPLASME; ELEMENTS; ENZYMES; EVEN-ODD NUCLEI; FUNCTIONS; Fundamental and applied biological sciences. Psychology; Hydrogen - metabolism; Hydrogenase - metabolism; HYDROGENASES; INTERMEDIATE MASS NUCLEI; ISOTOPE APPLICATIONS; ISOTOPES; METALS; MICROORGANISMS; Mission oriented research; NICKEL; Nickel - metabolism; NICKEL 63; NICKEL ISOTOPES; NIQUEL; NUCLEI; OXIDOREDUCTASES; OXIDORREDUCTASAS; OXYDOREDUCTASE; PHYSIOLOGY; Physiology and metabolism; PROTEINAS; PROTEINE; RADIOISOTOPES; Rhizobiaceae - metabolism; RHIZOBIUM; TRACER TECHNIQUES; TRANSITION ELEMENTS; YEARS LIVING RADIOISOTOPES 551001 > Physiological Systems-- Tracer Techniques
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.56.6.1905-1911.1990

Hydrogenase-derepressed (chemolithotrophic growth conditions) and heterotrophically grown cultures of Bradyrhizobium japonicum accumulated nickel about equally over a 3-h period. Both types of cultures accumulated nickel primarily in a form that was not exchangeable with NiCl2, and they accumulated much more Ni than would be needed for the Ni-containing hydrogenase. The nickel accumulated by heterotrophically incubated cultures could later be mobilized to allow active hydrogenase synthesis during derepression in the absence of nickel, while cells both grown and derepressed without nickel had low hydrogenase activities. The level of activity in cells grown with Ni and then derepressed without nickel was about the same as that in cultures derepressed in the presence of nickel. The Ni accumulated by heterotrophically grown cultures was associated principally with soluble proteins rather than particulate material, and this Ni was not lost upon dialyzing an extract containing the soluble proteins against either Ni-containing or EDTA-containing buffer. However, this Ni was lost upon pronase or low pH treatments. The soluble Ni-binding proteins were partially purified by gel filtration and DEAE chromatography. They were not antigenically related to hydrogenase peptides. Much of the 63Ni eluted as a single peak of 48 kilodaltons. Experiments involving immunoprecipitation of 63Ni-containing hydrogenase suggested that the stored source of Ni in heterotrophic cultures that could later be mobilized into hydrogenase resided in the nonexchangeable Ni-containing fraction rather than in loosely bound or ionic forms