The Structure of Rhodospirillum rubrum

Abstract

Cells from serial cultures of R. rubrum, grown anaerobically in the light, were harvested at intervals from ~/~ to 15 days and sectioned for electron microscopy by conventional methods.Cells of this species possess a multilayered outer envelope, and the external cell surface is differentiated into ridges extending parallel or obliquely to the long axis of the cell.Cells from very young cultures resemble non-photosynthetic bacteria and contain only a granular cytoplasm, scattered high-density particles, and lowdensity areas corresponding to the chromatin areas observed by light microscopy. They contain neither the chromatophores nor the lame]lar systems assumed by previous investigators to be characteristic of this species when grown anaerobically in the light.Chromatophores appear in cells from cultures older than about 12 hours, while systems of paired lamellae appear along with the chromatophores in cells from cultures older than about 8 days. Divergent opinions concerning the occurrence of chromatophores or lamellae in this species can be resolved on the basis of the age of cultures used in previous studies.Other changes occurring in ceils from cultures of increasing age include the appearance of granular and reticulate cytoplasmic bodies and vacuoles, extension of the chromatin areas, and the appearance of a single membrane enclosing several chromatophores.

Observations on the Relationship between the Formation of Photopigments and the Synthesis of Protein in Rhodopseudomonas spheroides

“…Electron micrographs of light grown Rhodopseudomonas spheroides or Rhodospirillum rubrum show the cytoplasm to contain round, electron transparent structures which increase in number as the pigment content of the cell increases. These structures are not seen in micrographs of aerobically grown cells (Hickman & Frenkel, 1959;Flexer, Sistrom & Chapman, 1960). Newton (1960) has shown that pigmented cells of R. rubrum contain antigens which are not present in aerobically grown cells.…”

OBSERVATIONS ON THE STRUCTURE OF RHODOSPIRILLUM RUBRUM

“…The circular cytoplasmic bodies shown here have been observed previously (7), and in some areas are connected to one another by lamellae which are continuous with the cytoplasmic membrane (arrow). OsO4 fixation.…”

“…As previously indicated (7) the ages of these cultures should be considered approximate and are used only to establish the relative ages of the cultures . Fig .…”

“…Cultures of RhodospiriIlum rubrurn strain S 1 van Niel were grown and sampled as previously described (7) exccpt that the medium was neutralized with NaOH instead of KOH. Incident light intensity was about 350 ft-c as measured with a Weston model 756 illumination meter .…”

“…It was later demonstrated that photochemically active chromatophores are also formed in cells grown in the dark under reduced oxygen tension (15). In addition to the formation of chromatophores, however, this organism is capable of further internal differentiation, and produces other internal structures whose physiological significance is undetermined (7).…”