A TRANSMISSION ELECTRON MICROSCOPY STUDY OF THE MICROBE-MINERAL INTERFACE IN THE RHIZOSPHERE OF PINE
Red pine trees were grown in columns in quartz sand amended with biotite and anorthite. Half of the trees were inoculated with Suillus tomentosus and forest soil bacteria, and the other half were left without microbial inoculation. Columns without any biology served as controls. Irrigation water contained Ca and K at 0, 10, 30 and 100% of amounts needed for healthy tree growth. After 3 months, a subset of columns was destructively sampled. Anorthite and biotite were collected from the rhizosphere of each tree and thin sections were prepared using focused ion beam – scanning electron microscopy (FIB-SEM). Several chemical profiles were analyzed on thin sections of the 0% treatment and a control with high resolution TEM and energy dispersive x-ray spectroscopy. Alteration of crystal structure was examined with selected area diffraction (SAD).
A slight decrease of Ca concentration is seen on the fungus-covered anorthite FIB sections, and a slight depletion of K, Mg and Fe is found on the biofilm-covered biotite FIB sections compared to controls. The differences between treatments and controls are not significant after 3 months reaction time, but indicate direct elemental uptake from solid mineral phases. The SAD results show alteration of the crystal structure at the biofilm-mineral interface on the biotite FIB sections that are not seen on the controls.