Subject(s)
Brain Abscess/drug therapy , Candidiasis/drug therapy , Drug Therapy, Combination/therapeutic use , Fungemia/drug therapy , Infant, Premature, Diseases/drug therapy , Amphotericin B/administration & dosage , Amphotericin B/therapeutic use , Brain Abscess/diagnosis , Brain Abscess/physiopathology , Candidiasis/diagnosis , Candidiasis/physiopathology , Drug Therapy, Combination/administration & dosage , Female , Fluconazole/administration & dosage , Fluconazole/therapeutic use , Flucytosine/administration & dosage , Flucytosine/therapeutic use , Fungemia/diagnosis , Fungemia/physiopathology , Humans , Infant, Newborn , Infant, Premature , Infant, Premature, Diseases/diagnosis , Tomography, X-Ray ComputedSubject(s)
Bacteria/analysis , Bacterial Proteins/analysis , Chlorophyll/analysis , Bacteria/cytology , Centrifugation, Density Gradient , Chlorophyll/isolation & purification , Electrophoresis, Polyacrylamide Gel , Isoelectric Focusing , Macromolecular Substances , Protein Binding , Spectrometry, Fluorescence , Spectrophotometry , Spectrophotometry, Ultraviolet , Subcellular Fractions/analysis , TemperatureABSTRACT
A photochemically active subcellular fraction has been isolated from the green bacterium Chloropseudomonas ethylica. It is enriched in bacteriochlorophyll a and contains only a small amount of Chlorobium chlorophyll. Both a reaction-center bleaching (P840) and a cytochrome oxidation (C553) are observed to occur in the fraction. Particles that are contained in the fraction are larger than 1.5 x 10(6) daltons and exhibit a range of sizes consistent with some form of polymeric association of similar subunits. Around 80 bacteriochlorophyll a molecules are present per P840. In an intact photosynthetic apparatus there are about 1000-1500 total chlorophylls (including Chlorobium chlorophyll) per reaction center. The redox potentials of the reaction center P840 and C553 were found to be 0.24 and 0.17 V, respectively, in one-electron reactions. The potentials of these components are around 0.2 V lower than comparable components found in other photosynthetic organisms.
Subject(s)
Bacteria/analysis , Chlorophyll/isolation & purification , Carotenoids/analysis , Centrifugation, Density Gradient , Microscopy, Electron , Oxidation-Reduction , Photochemistry , Spectrum AnalysisABSTRACT
The photoreduction and interaction with the photosynthetic "reaction center" of 2-amino,4-hydroxy-6-substituted pteridine indicates that these low-potential ( approximately -0.7 v), naturally occurring compounds play a primary role in photosynthetic electron transport. These unconjugated pteridines, which occur in association with the photosynthetic apparatus of green plants and photosynthetic bacteria, can be reduced by light in the presence of a bacterial chromatophore fraction from the dihydro form to the tetrahydro form. 6,7-Dimethyl-tetrahydropteridine readily reduces spinach ferredoxin. This compound also specifically interacts with reaction-center chlorophyll and bacteriochlorophyll and produces spectral shifts similar to those produced by light. It is proposed that the electron produced by excited-state chlorophyll is captured and separated by a pteridine at -0.67 v at the photosynthetic reaction center.
Subject(s)
Electron Transport , Photosynthesis , Pteridines , Chloroplasts , Euglena , Plants, EdibleABSTRACT
A known inhibitor of pteridine utilization (4-phenoxy,2,6-diamino pyridine) blocks the synthesis of colored carotenoids in the photosynthetic bacterium Rhodospirillum rubrum. In many ways the effect is similar to the inhibition of the synthesis of colored carotenoids by diphenylamine. This inhibition is probably independent of other effects of pteridine on photosynthetic electron transport since it is not as readily reversible as the total inhibition of photosynthetic activity by pteridine analogs.
Subject(s)
Carotenoids/biosynthesis , Photosynthesis/drug effects , Pteridines/antagonists & inhibitors , Rhodospirillum/metabolism , Darkness , Electron Transport/drug effects , Pyridines/pharmacology , Spectrum AnalysisABSTRACT
Radioautographic and radiochemical techniques were used to establish the presence of replicating DNA in the chloroplasts of Acetabularia mediterranea. These techniques also demonstrated that these chloroplasts synthesize RNA. It was found that label from thymine was also incorporated into DNA and RNA in these chloroplasts. With the establishment of protein and nucleic acid synthesis in Acetabularia chloroplasts, it is clear that these chloroplasts carry out those metabolic processes which are most characteristic of autonomous cells.
