Fine structure of in situ microbial iron deposits

Abstract

The fine structure of Fe deposits produced by Leptothrix spp. from 2 caverns and a surface spring were observed. In the case of L. pseudovacuolata, the Fe occurred as an amorphous deposit within the cell sheath and the cells contained gas vesicles. In the case of the other Leptothrix spp., the Fe was deposited within the cell sheath either as a hexagonal or fibrillar matrix. In the case of fibrillar Fe deposits, fibrils resembling those of the sheath were found within the cytoplasm of the cells. The deposition of Fe could have occurred within the cells and at the cell surface. In some cases, the fine structure of microbial Fe deposits could provide a means of distinguishing biological from abiological Fe deposition.