THIORHODACEAE: I. THE EFFECTS OF SODIUM THIOGLYCOLATE ON THE PHOTOSYNTHETIC AND DARK METABOLISM OF PURPLE SULPHUR BACTERIA

Abstract

Twenty-two pure cultures of purple sulphur bacteria were investigated for their ability to utilize organic sulphur compounds as hydrogen donors during photosynthesis. Of the 12 compounds tested, only sodium thioglycolate sustained growth of the organisms in the light.Carbon dioxide fixation by illuminated resting cells in the presence of endogenous sulphur or exogenous thiosulphate was inhibited by thioglycolate in proportion to its concentration. The fixation of carbon dioxide by illuminated sulphur-free resting cells harvested from thioglycolate media increased with the thioglycolate concentration to about 0.04 M, but was proportionally inhibited by higher concentrations.Non-illuminated suspensions of resting cells in the presence of endogenous sulphur or exogenous thiosulphate also assimilated carbon dioxide when thioglycolate was added. Inhibition of fixation appeared similar to that occurring in the light. Thioglycolate disappeared from the suspensions in proportion to the amount of bicarbonate assimilated. Thioglycolate-grown cells did not fix significant amounts of carbon dioxide under similar experimental conditions. Growth of the organisms was never demonstrated in non-illuminated thioglycolate media.