Paper No. 58
Presentation Time: 9:00 AM-6:00 PM

A TRANSMISSION ELECTRON MICROSCOPY STUDY OF THE MICROBE-MINERAL INTERFACE IN THE RHIZOSPHERE OF PINE


NIEDZIELA, Sheila M.1, DOHNALKOVA, A.2, GREENBERG, K.A.1, AREY, B.2, BALOGH-BRUNSTAD, Zsuzsanna1, SHI, Z.3 and KELLER, C.K.3, (1)Department of Geology and Environmental Sciences, Hartwick College, Oneonta, NY 13820, (2)Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, (3)School of the Environment, Washington State University, Pullman, WA 99164, NiedzielaS@hartwick.edu

Bacterial and fungal processes in weathering of minerals and in plant nutrient acquisition have been characterized in recent decades. However, the interactions of these processes in the rhizosphere are still poorly understood. In this study, we examined the mineral-fungus-biofilm interface using transmission electron microscopy (TEM). We hypothesized that a tree-fungus-bacteria association would increase biofilm formation under Ca and K limitations, and enhance mineral weathering as indicated by depletion profiles of elements beneath fungal and biofilm cover on mineral surfaces.

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.