Abstract
Deep subsurface oil reservoirs 100's of meters below Earth's surface exhibit extreme environmental conditions such as high temperature, high pressure, and high salinity. Still, these oil reservoirs are inhabited by a wide variety of microbial life.Microorganisms in oil reservoirs comprise relatively few dominant microbial species co-existing with a high number of relatively rare species. This rich pool of specially adapted microorganisms may contain species with functional potentials that are desirablee.g. during enhanced oil recovery, and for use in bioremediation. In addition, they may represent a vast source of potential noveland biotechnologically valuable microorganisms and robust enzymes for industrial applications. Thus, it is important to understand the composition and functions of the microbial communities in oil reservoirs.
High quality environmental DNA (eDNA) is a prerequisite for bioprospecting and studying microbial communities. In particular for the latter, representative samples are crucial. This becomes especially challenging when the environment of interest presentsextreme conditions, such as within deep subsurface oil reservoirs. Sampling such environments involves a pressure drop from highpressure (often higher than 200 bar) to ambient pressure (1 bar). This pressure drop may result in loss of viability, cell damage, DNA leaking from cells, and degradation of the liberated DNA. Pressurized sampling and controlled decompression has been successfully applied to obtain representative and good quality samples from such environments. However, costs related to pressurized sampling, requiring e.g., temporary stoppage of oil production, limit access to such samples. The effect of rapid decompression on microorganisms and options to recover high quality eDNA has, however, not been studied systematically. Hence, the actual needfor pressurized sampling has never been fully evaluated.
High quality environmental DNA (eDNA) is a prerequisite for bioprospecting and studying microbial communities. In particular for the latter, representative samples are crucial. This becomes especially challenging when the environment of interest presentsextreme conditions, such as within deep subsurface oil reservoirs. Sampling such environments involves a pressure drop from highpressure (often higher than 200 bar) to ambient pressure (1 bar). This pressure drop may result in loss of viability, cell damage, DNA leaking from cells, and degradation of the liberated DNA. Pressurized sampling and controlled decompression has been successfully applied to obtain representative and good quality samples from such environments. However, costs related to pressurized sampling, requiring e.g., temporary stoppage of oil production, limit access to such samples. The effect of rapid decompression on microorganisms and options to recover high quality eDNA has, however, not been studied systematically. Hence, the actual needfor pressurized sampling has never been fully evaluated.