The regulation of hydrogenase formation as a differentiating character of strains of Paracoccus denitrificans.

Paracoccus denitrificans strains Stanier 381 (DSM 65), Morris (DSM 413), and Vogt 11 (DSM 415) and eleven newly isolated strains were compared with respect to the localization of hydrogenase and its regulation. In all strains hydrogenase was found to be membrane-bound and not able to reduce pyridine nucleotides. The enzyme was inducible in strain 381 and was found only in cells grown with hydrogen as the sole hydrogen donor; in cells grown under mixotrophic or heterotrophic conditions the hydrogenase activity was zero.

Structural analysis of four strains of Paracoccus denitrificans.

Two out of eleven newly isolated strains of Paracoccus denitrificans were investigated by light and electron microscopic methods and compared with two strains of P. denitrificans already kept in culture collections. Samples were taken from different growth phases revealing short rods and nearly spherical cells in the exponential growth phase, and an increasing ratio of nearly spherical cells in the stationary growth phase.