Search

The role of adenine nucleotides in the control of the energy metabolism of Chromatium has been studied through the measurement of the levels of ATP ADP, and AMP in growing cultures. Comparison of these levels with the cellular chlorophyll levels indicates that ATP concentration, and not those of ADP, AMP, or any function of concentration of these three nucleotides, is a controlling factor in chlorophyll synthesis. In addition, the relationship of cellular ATP and chlorophyll levels to sulfur metabolism furnishes further evidence for the existence of two photosystems, postulated previously. The effects of high levels of exogenous ATP and ADP are consistent with these findings.

Sulfur particles extracted from Chromatium vinosum strain D were found to be bounded by a unique proteinaceous membrane. Ultrastructural examination of the membrane in Epon sections and bovine serum albumin sections and examination of negatively stained, sulfur-free membrane ghosts revealed a monomolecular sheet composed of 2.5-nm globular components. The internal sulfur was found to bind large amounts of a variety of negative stains and to form myelin-like structures upon rupture of the surrounding membrane.

Chromatium strain D was grown on autotrophic medium with sulfide as the sole electron donor and on heterotrophic media. The following growth parameters were monitored: sulfide, intracellular sulfur, cell number, bacteriochlorophyll, protein, storage polysaccharide, dry weight, and turbidity. In addition, electron micrographs of the bacteria at each stage of growth were prepared. The metabolism and structure of the bacteria were found to be dependent on whether sulfide or sulfur was the primary photosynthetic electron donor during growth as autotrophs. The major effects in shifting from sulfide to sulfur were noted as cessation of bacteriochlorophyll synthesis, decreased cellular protein content, and increased rate of cell division. Such effects were not seen in heterotrophic growth on succinate.

Sulfur particles were isolated from the purple sulfur photosynthetic bacterium,Chromatium vinosumstrain D. The composition of these particles was determined to be 93% sulfur, 5% protein, and 0.6% lipid. Gel electrophoresis indicated the presence of a single protein species with a molecular weight of 13,500 daltons. From these results, the sulfur particle is postulated to be bounded by a membrane consisting entirely of protein.

A circuit design is presented for a probe damper suitable for single coil NMR probes which improves the time for ringdown following an rf pulse by a factor of 2.5. The damping is provided for a precisely controlled time and removed positively to enable the use of high‐Q single‐coil NMR probes for samples with very short T2's. The damper can be adapted for use with negative or positive transmitter gating pulses.