[Ultrastructural organizational characteristics of the hydrogen thermophilic bacterium, Pseudomonas thermophila]

The ultrastructural organization of the lithotrophic hydrogen bacterium Pseudomonas thermophila K2 was described for the first time and was found to be typical of Gram-negative bacteria. The ultrastructure of this organism is characterized by (i) irregular plication of the outer membrane of the cell wall and a very thin (2-3 nm) rigid layer; (ii) a considerable number of intracellular membranes differing in their structure and location; (iii) fragmentation of the cytoplasm involving the plasmalemma and the cell wall; (iv) the presence, in the nucleoid zone, of paracrystals having a hexagonal shape and resembling carboxysomes in their size, shape and macromolecular organization, which had not been found in hydrogen bacteria hitherto.