Presence of rhapidosomes in various species of bacteria and their morphological characteristics.

Rod-shaped structures have been observed in cells of Pseudomonas, Photobacterium, Proteus, and Saprospira by use of the negative-contrast stain. These structures, referred to as rhapidosomes, appear to be normal components of these cells. Other bacteria including Escherichia, Salmonella, Shigella, Klebsiella, Micrococcus, Bacillus, Mycobacterium, Rhodospirillum, and Hydrogenomonas genera failed to reveal these structures. The rhapidosomes of Saprospira were found to consist of two rods, one encasing a narrower, longer structure. In contrast, the rhapidosomes of Pseudomonas, Proteus, and Photobacterium were without the rigid inner structure, but were occasionally seen filled with a homogeneous material as observed by the negative stain. Ultrathin sections of Pseudomonas cells indicate that these rhapidosomes are embedded within or are in close association with the nucleoplasm.