Lichtgedanken 03

S C HW E R P U N K T 40 Rocks and microbes For a long time, geosciences and biology were seen as separate disci- plines, one focusing on the abiotic world of rocks and minerals and the other on the living world. However, it has gradually become appa- rent that the two disciplines have more in common than previously thought. Microbiologists from the University of Jena, for example, are studying how bacteria form minerals and how fungi break down rocks. BY SEBASTIAN HOLLSTEIN Rock formation is generally conside- red to be a geological process, in which biological processes barely play a role. It has become clear, however, that microorganisms can also form minerals such as calcite (calcium carbonate) in freshwater springs. This mineral is pre- sent in many types of rock, for example in travertine (see box p. 43). Carbona- te is normally precipitated when cold groundwater reaches the surface and becomes warmer there. With the help of microbial processes, carbon dioxide and