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Abstract

With the rapidly increasing utilization of the subsurface, either for exploitation of natural resources or long-term storage of waste products, it is of paramount importance to understand this so far understudied environment. Over the last two decades new findings have shown that microbes mediate many processes that were previously considered as abiotic. Exploration of the so-called Deep Biosphere is only possible through drilling. With regard to drilling operations and sample processing, microbiology has different requirements than many other scientific disciplines, the most important one being contamination control because drilling fluid tends to infiltrate the drill core and renders the material unsuitable for microbiological analyses. There are different ways to assess the infiltration of drill fluid, each one has its specific advantages and disadvantages. Another important aspect of deep biosphere research is the necessity to process samples as quickly as possible after retrieval to avoid any changes in the microbial community. These requirements add some complications to drilling operations, therefore the addition of a geomicrobiological component is not always appreciated by all members of a science party. However, knowledge about the drivers of diagenetic processes and accurate assessment of the contamination of the core by drilling fluids are valuable information for other disciplines as well.