X-ray tomography of a microhabitat of bacteria and other soil colloids with sub-100 nm resolution.

Visualization of the spatial arrangement of bacteria and other colloids permits to describe relevant soil parameters like porosity or nutrient storage capacity. Major advantages of X-ray microscopy for these investigations are the much higher spatial resolution compared to visible light microscopy and its ability to study colloidal structures directly in aqueous media. To obtain information about the three-dimensional structure of the microhabitats formed by bacteria and other soil colloids, tomography based on X-ray microscopy images with about 45 nm resolution was performed. Tomographic reconstructions presented in this paper clearly reveal the spatial arrangement of bacteria and other soil colloids which cannot be obtained from two-dimensional projections. The results show that X-ray nanotomography is a very powerful tool for examining the three-dimensional structure of flocs of colloidal particles.