ELECTRON-DENSE GRANULES IN DESULFOVIBRIO-GIGAS DO NOT CONSIST OF INORGANIC TRIPHOSPHATE BUT OF A GLUCOSE PENTAKIS(DIPHOSPHATE)

Under certain growth conditions the sulfate-reducing bacterium Desulfo vibrio gigas forms electron-dense granules in the cells which had been claimed to consist of a magnesium triphosphate). We observed granules after cultivation in media with a low Fe2+ or NH4+ concentration and reinvestigated the nature of the electron-dense bodies. Energy-dispers ive X-ray analysis of the granules in the cells showed that they conta in large amounts of P, Mg, and K. Gel electrophoresis and chromatograp hic analyses of isolated granules which had been dissolved in 20 mM ED TA, however, revealed discrepancies with commercially available polyph osphates. P-31-NMR spectra also lacked the peaks in the -22-ppm region which are characteristic for inner phosphates of polyphosphates confi rming that the phosphocompound as isolated from the electron-dense bod ies of D. gigas did not consist of polyphosphates. Using multinuclear NMR spectroscopy we showed that the electron-dense bodies of D. gigas contained a novel metabolite which was identified as a-glucose 1,2,3,4 ,6-pentakis (diphosphate).