Distribution of bacteriochlorophyll a among aerobic and acidophilic bacteria and light-enhanced CO₂-incorporation in Acidiphilium rubrum

Four Acidiphilium species among aerobic and acidophilic bacteria, Acidiphilium angustum, Acidiphilium cryptum, Acidiphilium organovorum, and Acidiphilium rubrum, produced the bacteriochlorophyll a (0.005 ~ 0.76 nmol mg^-1 dried cells), whereas Acidiphilium aminolytica, Acidiphilium facilis, Acidomonas methanolica, Acidobacterium capsulatum. Thiobacillus acidophilus, Thiobacillus ferrooxidans, and Thiohacillus thiooxidans produced no phototrophic pigments. Bacteriochlorophyll a was purified from A. rubrum to a single spot on a thin-layer chromatogram and identified by its absorption spectrum. Light enhanced ¹⁴CO₂-incorporation in A. rubrum only under aerobic conditions. However, the rates of incorporation were very low compared with anaerobic phototrophic bacteria and A. rubrum could not grow either aerobically or anaerobically in light in the absence of an organic energy source. These results indicate that four Acidiphilium species produced bacteriochlorophyll a should be classified into quasi-photosynthetic bacteria.