Assembly of plasmid DNA and chromatophore inRhodospirillum rubrum

Abstract

Summary. Rhodospirillurn rubrum, a photosynthetic bacterium, contains many photosynthetic vesicular membranous structures called chromatophores. The organism contains a 55 kb specific plasmid which is essential for photosynthesis, but the exact relationship between the chromatophore and the plasmid is uncertain. In this study we examined the precise localization of the plasmids, especially in relation to the chromatophores. Fluorescence in situ hybridization indicated that there are several copies of the plasmid per cell and that some plasmids are localized close to the cellular envelope. In situ hybridization at the electron-microscopic level further revealed that the plasmid localized to the periphery of the chromatophore close to the envelope. Moreover, when the chromatophore fraction was purified from cells, the plasmid DNA was observed as a cluster around the chromatophore vesicles. The assembly of the plasmid and chromatophore may be related to chromatophore formation by invagination of cell membrane.

Three‐dimensional architecture of ribosomal DNA within Barley Nucleoli Revealed with Electron Microscopy

“…In situ hybridization was performed as described by Iwano et al (2000) with the addition of a pretreatment with proteinase K (1 mg/ml) at 37°C for 20 min and a subsequent incubation in RNase A (3 mg/ml) at 37°C for 1 h. Following washing with 2 × SSC, samples were mounted on a glass slide. The hybridization mixture was layered onto the grids and covered with a coverslip at 37°C.…”