The Preparation and Properties of Bacterial Chromatophore Fractions

Abstract

Chromatophore material from the bacterium Rhodopseudomonas spheroides was freed of ribosomes by centrifugation in 27 per cent RbC1 and then separated into "heavy" and "light" fractions by centrifugation through a sucrose gradient. The fractions differed from one another in the following ways. (a) The isopycnic density of the heavy fraction was between 1.15 and 1.18 gm/ml and that of the light fraction was 1.14 gm/ml. (b) The heavy fraction was able to bind ribosomes; the light fraction was not. (c) The light fraction was homogeneous in the ultracentrifuge and had a sedimentation constant, extrapolated to infinite dilution, of 153 s20,w. The heavy fraction was grossly heterogeneous. (d) Both the amount of bacteriochlorophyll relative to protein and the ratio of bacteriochlorophyll to carotenoids were greater in the light fraction. (e) The spectra of the two fractions in the near infra-red were different. Comparisons of the chromatophore fractions from cells with different amounts of bacteriochlorophyll showed that the specific bacteriochlorophyll contents of the two fractions did not change to the same extent as did that of the whole cells. The amount of heavy fraction from pigmented cells was roughly independent of the cellular pigment content and was about equal to that from pigment-free cells. The amount of light fraction depended on the pigment content of the cells; no light fraction was obtained from cells devoid of bacteriochlorophyll. The cytochrome complements of both fractions underwent quantitative as well as qualitative changes with varying growth conditions. The size of the photosynthetic unit in R. spheroides appeared to increase as the total cellular bacteriochlorophyll content increased; however, the number of units per light fraction particle remained constant.

THE PHOTOSYNTHETIC APPARATUS OF RHODOSPIRILLUM MOLISCHIANUM

“…terial is independent of its BChl content, which was found by Worden and Sistrom (16) to be the case in Rhodopseudomonas spheroides.…”

“…This is what would be expected if BChl and the enzymes of the respiratory chain were built into the same membranes. Worden and Sistrom (16) have also obtained indirect evidence that BChl is present on both the cell membrane and the internal membranes of Rhodopseudomonas spheroides.…”

“…The preparation of cell free extracts and chromatophore material was carried out as described by Wordcn and Sistrom (16), with some minor modifications. The cells were suspended in TSM buffer (0.02 M tris -(hydroxymcthyl) -aminomcthane, 0.01 M MgSO4, and 0.08 M NaCl; pH, 7.8) and ruptured in a French pressure cell at 20,000 lb/in.…”

Physiological role and potential clinical interest of mycobacterial pigments

“…During the same decade, the blue pyocyanin extracted from Bacillus pyocyaneus had been described to increase cell respiration and violacein extraction from Bacillus violaceus was described in 1935 (12,13). In 1952, the photopigments of the photosynthetic bacterium Rhodospirillum rubrum were associated with particulate cellular extracts later named chromatophores (14) opening a series of various studies in the 1960s that were carried on bacterial chromatophore fractions (15,16). While deep investigations on the Serratia marcescens prodigiosin were still going on (17,18), pigmentation mutants of bacilli and staphylococci were appearing to be extremely helpful to the exploration and understanding of bacterial pigments biology (19,20).…”

Studies of photosynthetic energy conversion. Comprehensive three-year report, September 1, 1972--August 31, 1975

“…spheroides, when analyzed in this way, displayed at least 50 distinguishable protein components including the three reaction center proteins. A purified pigmented membrane fraction equivalent to Worden and Sistrom 1 s "light chromatophores" (38) or Fraker and Kaplan's "purified chromatophores" (39) showed about 15 bands; predominant were the three of reaction centers and one at about 10,000 dalton (6). "Crude" chromatophores contained these and others; especially a major component at 46,000 dalton.…”