[Fine structure of Chloroflexus aurantiacus var. mesophilus (nom. prof.) grown in the light under aerobic and anaerobic conditions].

The fine structure was studied in two mesophilic strains of Chloroflexus aurantiacus var. mesophilus (nom. prof.): KN-4 and BR-1. Trichomes are covered with a mucous fibrillar sheath which is more developed in the KN-4 strain. Photosynthetic structures, "chlorobium-vesicles", are located at the periphery of the cells of both strains. The structure of the cell was is typical of gram-negative microorganisms. By their electron density and dimensions, inner cytoplasmic structures are identified as poly-beta-hydroxybutyric acid, polyphosphates, and polysaccharides. When the strain BR-I was grown in aerobic conditions in the light, "chlorobium-vesicles" were not synthesized and intracytoplasmic membranes were represented by small tubular-vesicular invaginations. When the cells were grown under anaerobic conditions in the lgiht, numerous "chlorobium-vesicles" were formed, and additional large vesicular membrane systems appeared; these systems occupied over 20 per cent of the cell volume. Possible relationship between the membrane structures and the synthesis of bacteriochlorophyll a and c is discussed.