Sulfate-reducing bacteria (e.g. Desulfotomaculum acetoxidans) exist in animal intestine. These bacteria are able to bind heavy metals (e.g. cadmium or lead). Comparative investigations on the composition of cellular walls of Desulfotomaculum acetoxidans - depending on the initial Fe2+ supplement in the medium (7.5, 57.5 and 507.5 M) were performed. Iron(II) was cumulated as FeS or as pyrite (FeS2). However, if the initial amount of iron was higher, its majority (46% 85%) was transported onto the membrane. It was determined that the siderophore found in Desulfotomaculum acetoxidans was deferroxamine as in animals.