Bacteriochlorophyll (Bchl) a was found in strains of the strictly aero
bic acidophilic heterotrophic bacteria: Acidiphilium rubrum, A. angust
um, and A. cryptum. Absorption spectra of the cell-free extracts showe
d a large peak at 865 nm and a small peak around 802 nm. Anaerobic gro
wth was not observed in either the light or the dark. Bchl a was not d
etected in either A. organovorum or A. facilis. Bchl a contents were l
ess than ca. 0.7 nmol/mg dry cell weight, being variable among the spe
cies.