SELECTIVE ACCUMULATION OF IRON ION INTO THE CELL WALL OF CLOSTRIDIUM SACCHAROPERBUTYLACETONICUM ATCC 13564

Abstract

The relative amounts of metals in the cell wall of Clostridium saccharoperbutylacetonicum ATCC 13564 were found to be as follows: Fe>Al_??_Mg>K>Na>Ca_??_Zn>Cu>Hg_??_Mn>Co. Of particular note here is the very high Fe content and the specific Fe-binding properties of cell wall. The iron physiology in cell wall was somewhat different from those of Mg and Cu, which were used for comparison. The in vivo accumulation of Fe into cell wall increased vigorously after 6hr of cultivation (early to middle log phase) and continued until the late stage of the log phase (about 15hr). The maximum content was ca. 1100μg/g of dry weight of cell wall, when Fe²⁺ was supplemented to the medium at 3.6×10^-5M. In vivo accumulation of Mg increased in the first 6hr of cultivation, and then decreased. Its maximum content was ca. 360μg/g, when Mg²⁺ was supplemented at 1.2×10^-3M. The accumulation of Fe and Mg was closely related to the cell growth. On the other hand, toxic Cu rapidly bound to cell wall for initial short periods regardless of the growth phase. Its maximum content was ca. 60μg/g when no Cu²⁺ was added; when Cu²⁺ was intentionally supplemented at 2×10^-5M, its maximum content was ca. 200μg/g. The relative metal binding in cell walls in vitro was in the order of Cu²⁺>Fe²⁺>Mg²⁺. Fe had a high affinity with the peptidoglycan moiety of the cell wall. Mg had some affinity to the polysaccharide moiety of the cell wall. Cu seemed to have a high affinity with some unidentified constituents of the cell wall.