The Magnetotactic bacterium Magnetospirillumgryphiswaldense (MSR-1) mineralizes the magnetite (Fe(3) O(4)) crystals and organizes a highly ordered intracellular structure, called the magnetosome. Iron transport system supports the biogenesis of magnetite. Although iron is an essential trace element for many metabolic pathways of the body, increase or decrease in iron will cause many diseases. Mice were infected by MSR-1 to study survival of bacteria in mice when injected by different routes. The aim of this study was to investigate whether bacterial magnetite formation could take up Fe(2+) ions from the blood an animal model.In this study, MSR-1 at a dose lower than LD(50) in 200 µl volume of PBS buffer was injected as intravascular (i.v), peritoneal (i.p) and subcutaneous (s.c) in mice. Number of viable bacterial was determined in organs such as liver, spleen and lymph node by measuring colony-forming unit (CFU). Moreover, serum iron level was evaluated by using commercial kits.According to CFU measurements, after 96 hours, mice can clear MSR-1 from their body with different routes of injection. We have also shown that MSR-1 bacteria can affect the blood iron level in mice. The serum iron level decreased from control level in the first 24 h after i.v injection (P< 0.05). Our research on optimizing the biological magnetic system is still continuing.