90 THE BACTERIAL PHOTOCHEMICAL APPARATUS 



It is, therefore, not surprising that when ultra-thin sections of 

 photosynthetic bacteria were eventually examined in the electron micro- 

 scope the interpretation of the observed intracellular structures was 

 strongly influenced by earlier work on isolated chromatophores. For 

 example, Vatter and Wolfe (4), who performed the first extensive 

 study of fine structure in purple bacteria, stated that: "... the cyto- 

 plasm [of Rho do spirillum ruhrum ] is organized into discrete units 

 which appear less dense than the cytoplasm and are surrounded by a 

 membrane. Since these structures are of the size of the isolated chro- 

 matophores of Schachman et al., they are believed to be identical with 

 them and to represent the chromatophore arrangement which exists 

 within the cell," 



The studies of Vatter and Wolfe (4), Bergeron (5), and Drews (6) 

 established the presence of abundant membrane-bounded vesicles of 

 low electron opacity in the cytoplasmic region of photosynthetically 

 grown cells of several purple bacteria: i?.« rubrum,Rhodopseudomonas 

 spheroides , and Chromatium strain D. However, this is not a universal 

 feature of internal structure in purple bacteria. As shown by Drews (6), 

 Vatter, Douglas and Wolfe (7), and Boatman and Douglas (8), Rhodo- 

 spirillum molis chianum and Rhodomicrobium vannielii do not contain 

 such elements; instead, thin sections reveal the presence of regularly 

 disposed lamellae, the intracellular arrangement of which is character- 

 istic for each species. These structures resemble the lamellar sys- 

 tems found in the cytoplasm of blue-green algae, which likewise 

 assume special patterns characteristic of the different species, as 

 shown by the work of Ris and Singh (9), 



When Schachman et al. (2) first isolated and described bacterial 

 chromatophores, it was not recognized that ultrasound and mechanical 

 abrasion do not simply break bacterial cells open; these treatments 

 also comminute, to a greater or lesser extent, the internal structures. 

 The comminutive effects of these methods of cellular breakage could 

 be clearly appreciated only after the effects of the much gentler pro- 

 cedure of osmotic lysis on cell structure had been explored, a field 

 that was opened by the work of Weibull in 1954 (10), In the light of 

 subsequent knowledge about bacterial cell structure, it is by no means 

 evident that the chromatophores as defined by Schachman et al. do in 

 fact exist as discrete structural entities in the intact cell; they could 

 be physical artifacts, produced by the fragmentation of larger struc- 

 tural elements during the treatment employed for breakage of the 

 cells. This possibility was first recognized by Karunairatnam et al. 

 (11), as a result of their observation that lysed spheroplasts of /?. 

 ruhrum retain essentially all of the photosynthetic pigment system. 

 At about the same time, we independently performed similar experi- 

 ments with R. ruhrum and Rhodopseudo))2onas splieroides ,'mthsimila.r 

 findings. In the case of Rhodopseudomonas spheroides, we observed 

 that the cellular inclusions of poly-/3-hydroxybutyric acid, which are 



