An immunocytochemical ultrastructural study of Rhodospirilum rubrum cultured under semiaerobic conditions was conducted to correlate the localization of functional components with membrane formation. R. rubrum is a facultatively phototrophic organism. Under reduced oxygen, this bacterium forms an intracytoplasmic chromatophore membrane that is the site of the photosynthetic apparatus. Immunogold techniques were used to localize intracellular protein antigens associated with the photosynthetic apparatus. Antibody, demonstrated by immunoblotting to be specific for the reaction center and light-harvesting photochemical components, was conjugated to colloidal gold particles and used for direct immunolabeling of fixed, sectioned specimens. Membrane invaginations appeared by 4 h after transition to induction conditions, and mature chromatophore membrane was abundant by 22 h. The occurrence of chromatophore membrane was correlated with bacteriochlorophyll a content and the density of the immunolabel. In uninduced (aerobic) cells and those obtained from cultures 0.5 h posttransition, the immunogold preferentially labeled the peripheral area of the cell. In contrast, in cells obtained after 22 h of induction, the central region of the cell was preferentially immunolabeled. These findings provided immunocytochemical evidence supporting the hypothesis that the chromatophore membrane is formed by invagination of the cytoplasmic membrane.Rhodospirillum rubrum is a facultatively photosynthetic bacterium that has been used as a model in studies of membrane structure and formation (22,36). Under aerobic conditions nonpigmented cells undergo chemotrophic metabolism. Under anaerobic conditions in the light, R. rubrum grows phototrophically. Bacteriochlorophyll a (BCHL) and carotenoids and associated proteins are localized in the intracytoplasmic chromatophore membrane. Ultrastructural and physical evidence has suggested that this chromatophore membrane is continuous with the cytoplasmic membrane (for a review, see reference 39). Moreover, studies revealing the opposite asymmetry of the chromatophore and cytoplasmic membranes in R. rubrum (34, 42) and other photosynthetic bacteria (8,11,25) imply the existence of a membrane continuum because the cytoplasmic face of the chromatophore membrane forms the outer surface of isolated chromatophores.The apparent continuity between the chromatophore and cytoplasmic membrane has led to the hypothesis that the chromatophore membrane is formed by invagination of the cytoplasmic membrane (35). Evidence to support this hypothesis is provided by the freeze-etching studies of Golecki and Oelze (13 Electron microscopy. Cells were harvested, washed, and suspended in a minimal amount of 10 mM potassium phosphate buffer (pH 7.0) and held at 0°C until cell blocks were prepared with 2% agarose (Seakem HGT; FMC Corp., Marine Colloids Div., Rockland, Maine). Double-distilled water used in all reagents was boiled for 10 min and filter sterilized. For cell block preparation, cell suspensions were broug...

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The effect of different concentrations of lead was investigated in two different ways in the leaves of Helianthus annuus plants. In the first way, removed leaf discs from 5-wceks old plants were floated in 0.05, 0.25, 2.50 and 5.00 mM PbNO3 solutions for 2, 4 and 6 days. In addition, the chlorophyll content and the activity of peroxidase enzyme which are the parameters of stress conditions in plants were also measured. In this experimental series, a decrease was determined in polyamine and chlorophyll contents and in the peroxidase activity in leaf discs which were treated with different concentrations of lead. In the second experimental series, one half of the upper leaves of 5-wceks old plants were used for lead treatments, while the other half for control. In half leaf experiments, lead in 0.05, 1.25 and 5.00 mM concentrations were sprayed to the both sides of the half leaves. According to the results of the half leaf experiments, 0.05, 1.25 and 5.00 mM lead treatments increased the putrescine content in 27, 15 and 9 % respectively. On the other hand, chlorophyll content and the activity of peroxidnse enzyme were decreased with the treatments of lead.