Formation of single-domain magnetite by a thermophilic bacterium

Magnetite is a common product of bacterial iron reduction and may serve as a potential physical indicator of biological activity in geological settings. Here the authors report the formation of single-domain magnetite under laboratory conditions by a thermophilic fermentative bacterial strain TOR-39 that was isolated from the deep subsurface. Time-course analyses were performed at 65 C to study the effect of bacterial activity on solution chemistry and magnetite formation during the growth of TOR-39. Run products were examined by transmission electron microscopy. Magnetite particles formed exclusively outside of bacterial cells and exhibited octahedral shapes having relatively equal length and width (