Oxidation of Alcohols by Non-Sulfur Photosynthetic Bacteria.

Carbon dixoide is reduced anaerobically to cell substance and water by the hydrogen donor H%A through the agency of photosynthetic pigments with the absorption of radiant energy. Two more or less clear-cut groups ca be distinguished among the purple bacteria on the basis of their physiological characteristics. One group, the sulfur purple bacteria (family Thiorhodeae Molihch, 1907) can develop in strictly inorganic media containing H,S or other reduced sulfur compounds, whereas the non-sulfur purple bacteria (family Atthiorhodaceae Molisch) require organic substrates as hydrogen donors. The distinction is, however, not rigid because (1) the sulfur purple bacteria can all utilize, organic substrates instead of sulfide (Muller, 1933; Gaffron, 1935; van Niel, 1936), and (2) vaious non-sulfur purple bacteria can accomplish photosynthesis with molecular hydrogen as hydrogen donor. It is now recognized that the non-sulfur purples represent a group of bacteria possesing quite heterogeneous physiological properties (van Niel, 1941, p. 280). Until recently, studies of the metabolism of photosynthetic purple bacteiria on organic substrates have dealt exclusively with salts of simple organic acids. This paper deals with the isolation of non-sulfur purple bacteria capable of attacking various alcohols for the photosynthetic reduction of C02, and with some of their physiological aspects. Of especial interest was the isolation of one organism which quantitatively converts isopropanol into acetone with the concomitant reduction of CO2 in the light (Foster, 1940).