Mineral-microbe interactions: Bacterially induced hydration of biotite

The interaction between microbes and minerals occurring in the soil is an important geochemical process in the Earth’s surface system. Investigating the weathering of potassium-bearing silicate minerals by microorganisms is of great importance in understanding the process of soil development and the provision of nutrient for plants. One of the major gaps in studies of weathering is the lack of sufficient evidence from X-ray diffraction to indicate of the formation of secondary minerals in the weathering of primary minerals. The present study aims to investigate whether or not secondary minerals formed during laboratory experiments can be detected by XRD (X-ray diffraction, XRD). For this reason, a series of culture experiments using biotite and Paenibacillus mucilaginous strain YM-1 were performed over a period of 450 days. The results demonstrate that preliminary treatment by sedimentation-centrifugation according to Stokes’s law to enrich the fine particles with grain size less than 1 μm and subsequent detection by XRD are practicable methods for investigating the presence of secondary minerals. The XRD results of the fraction with grain size less than 1 μm indicated that a part of the biotite flakes altered into hydrobiotite on day 60 in experiments with strain YM-1, while hydrobiotite occurred on day 390 for experiments without bacteria. In summary, it is demonstrated that strain YM-1 of Paenibacillus mucilaginous evidently accelerated biotite weathering.