DeepEarthshape: Geomicrobiology "Iron-metabolizing bacteria as a driving force in weathering of silicate minerals"

• Applicants: Professor Dr. Andreas Kappler, since 4/2020; Professor Dr. Thomas Neumann
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 408245216

Decades of previous research have elucidated that microorganisms play a crucial role as weathering agents in geological environments, in part due to their ability to catalyse redox transformations of metals contained within minerals. Much of the previous work on this process has focused on the microbial oxidation of free Fe2+ or reduction of iron oxides, or the effect of Fe(III)-reducing bacteria on clay minerals. Whilst these are important aspects of the weathering process, these minerals are themselves weathering products. Fe-metabolizing bacteria could also contribute extensively to early formation of soil parent material, but the extent to which this is possible is undetermined. Furthermore, the distribution, abundance and identity of these bacteria relative to the stage of soil development (thus nature of the available iron source) is almost completely unknown, especially on the oxidative side of the microbial iron cycle. Much of this lack of ecological understanding results from the fact that Fe-metabolizing bacteria often have low abundance in the overall microbial community despite their important biogeochemical impact. Determination of the potentially large impact of Fe-metabolizing processes on soil development requires a targeted combination of sensitive molecular- and cultivation-based approaches towards these specific microorganisms. Cultivation of many of these organisms, however, can only be done with specialist techniques.We hypothesize that the Fe-metabolizing bacterial community will co-evolve with the geological environment during soil development, and that their activity, in turn, will enhance the rate of soil development. We also suggest that the identity and physiology of the Fe-cycling community members will be strongly influenced by climate, thus their contribution to soil formation will differ as a function of this. Therefore, we propose to use the dramatic climate gradient of the Chilean coastal cordillera to determine the correlation between the abundance, distribution and identity of Fe-metabolizing bacteria with the nature of the iron source throughout the weathering profile (from surface to bedrock) under four different climate regimes. We will then utilize microcosm experiments to quantify the effect of these bacteria on weathering rates of Fe-silicate minerals and mineral transformation. Ultimately, we aim to demonstrate how these specialized bacteria act to shape the Earth’s surface.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1803: EarthShape: Earth Surface Shaping by Biota
• International Connection: Chile
• Cooperation Partners: Dr. Francisco Matus; Dr. Carolina Merino
• Ehemalige Antragstellerin: Casey Bryce, Ph.D., until 4/2020