Accumulation of Fe, Cr and Ni Metals inside Cells of Acidophilic Bacterium Acidiphilium rubrum that Produces Zn-Containing Bacteriochlorophyll a

The accumulations of metals were studied in cells of aerobicacidophilic proteobacterium Acidiphilium rubrum; this spicesuses Zn, instead of Mg as the central atom of bacteriochlorophyllin its photosynthetic apparatus. Energy dispersive X-ray analysis(EDX) of the cell surfaces gave peaks of P, S, Si and Mg. Transmissionelectron micrograph images showed a high density globule of0.11µm in diameter in each 1.1 x 0.3µm cell. AnEDX analysis of the black precipitate that was collected afterthe centrifuga-tion of disrupted cells showed high amounts ofthe heavy metals Fe, Cr, Ni and traces of K, Ca, P, Si and Alin the order of atomic content. An X-ray powder diffractionanalysis indicated that Fe, Cr and Ni exist as alloys. The metalaccumulations interpret the high tolerance of this bacteriumto the toxic heavy metals abundant in acidic growth medium.Zn seems to specifically exist as Zn-bacteriochlo-rophyll ain this organism, because no significant accumulation of Znwas detected on the cell surface, black precipitate, or cytoplasmicmembranes. (Received December 26, 1997; Accepted April 21, 1998)