Bacteriochlorophyll and photosynthetic reaction centers in Rhizobium strain BTAi 1

Rhizobium strain BTAi 1, which nodulates both stems and roots of Aeschynomene indica L., formed bacteriochlorophyll and photosynthetic reaction centers resembling those of purple photosynthetic bacteria when grown aerobically ex planta under a light-dark cycle. Bacteriochlorophyll formation was not observed under continuous dark or light growth conditions. The amount of pigment formed was similar to that previously found in aerobic photosynthetic bacteria. Stem nodules appear to fix nitrogen photosynthetically, as illumination of A. indica stem nodules with near-infrared light resulted in an enhanced rate of acetylene reduction. Near-infrared light did not enhance acetylene reduction when either A. indica or soybean root nodules were illuminated. The BTAi 1 isolate can be differentiated from members of the family Rhodospirillaceae by several criteria.