Biology subjects

Bartholomaeus, A.

Publications and source records attributed to Bartholomaeus, A..

3 recordsLinked to original sources

bioRxiv2025

Microbial Diversity and Community Shifts in a Petroleum Reservoir under Production: Effects of Water Breakthrough and Anthropogenic Alterations

Subsurface petroleum reservoirs host indigenous microorganisms that survive extreme conditions and long-term isolation. Microbial activity in these environments can contribute to adverse effects such as oil biodegradation and reservoir souring. Unlike the broader deep biosphere, oil reservoirs are frequently subjected to anthropogenic disturbances, particularly during production processes like water injection, which introduces external microbes and electron acceptors. In this study, we investigated microbial diversity, community structure, and the impact of water breakthrough in the Edvard Grieg oil reservoir offshore Norway using 16S rRNA gene and metagenomic sequencing. We found clear regional heterogeneity in community composition, with low diversity dominated by thermophilic, anaerobic, and halotolerant taxa. The southern region (wells A13, A17, A18, and A19) exhibited lower diversity, while well A07 showed a distinct microbial signature. The dominant genera included the strictly anaerobic bacterium Thermoanaerobacter and the hyperthermophilic archaeon Thermococcus. Water breakthrough triggered shifts in community structure, not due to widespread replacement by injected microbes, but via the increase of sulfate-reducing bacteria. Metagenomic data supported these observations and suggested rapid microbial transport between injection water and the water separator. These findings support the use of microbial signatures as cost-effective tools for monitoring oil reservoir processes and integrity.

microbiology↗

bioRxiv2025

Microbial Worlds Apart: Distinct Communities in Crude Oil and Production Waters

Genomic analyses of microbial community composition are used to improve oil reservoir engineering and monitor reservoir dynamics. Given the challenges of extracting nucleic acids from oil, production water samples are often used as proxies from which to infer microbial community information from oil reservoirs. We employed 16S rRNA gene amplicon and metagenomic sequencing on samples of crude oil and production water from four North Sea oil fields. Taxonomic profiling revealed differences in microbial compositions and functions between production water and crude oil. Production water was more homogeneous, less diverse, harboured taxa associated with conditions non-native to the reservoir (e.g., seawater), and exhibited evidence of contact with atmospheric oxygen, most likely from passing through the water separators. Conversely, crude oil samples harboured microbial taxa typically associated with oil reservoirs. Despite long-term production and, in some cases, re-injection of production waters, the putative native microbial communities were still present in the oil. These findings demonstrate that crude oil samples are much more representative of oil reservoir microbiomes than their production water proxies.

microbiology↗

bioRxiv2022

Microbial diversity and community dynamics in an active, high CO2 subsurface rift ecosystem

The Eger Rift subsurface is characterized by frequent seismic activity and consistently high CO2 concentrations, making it a unique deep biosphere ecosystem and a suitable site to study the interactions between volcanism, tectonics, and microbiological activity. Pulses of geogenic H2 during earthquakes may provide substrates for methanogenic and chemolithotrophic processes, but very little is currently known about the role of subsurface microorganisms and their cellular processes in this type of environment. To assess the impact of geologic activity on microbial life, we analyzed the geological, geochemical, and microbiological composition of rock and sediment samples from a 240 m deep drill core, running across six lithostratigraphic zones. In addition, we evaluated diversity as well as metabolic attributes of bacterial and archaeal communities. Our investigation revealed a distinct low biomass community, with a surprisingly diverse Archaea population, providing strong support that methanogenic archaea reside in the Eger subsurface. Geochemical analysis revealed sulfate and sodium concentrations as high as 1000 mg L-1 in sediment samples from a depth between 50 and 100 m and in weathered rock samples collected below 200 m. Most microbial signatures could be assigned to common soil and water bacteria, which together with the occurrence of freshwater Cyanobacteria at specific depths, emphasize the heterogenous, groundwater movement driven nature of this terrestrial subsurface environment. Although not as frequently and abundantly as initially expected, our investigations also found evidence for anaerobic, autotrophic, and acidophilic communities in Eger Rift sediments, as sulfur cycling taxa like Thiohalophilus and Desulfosporosinus were specifically enriched at depths below 100 m. The detection of methanogenic, halophilic, and ammonia oxidizing archaeal populations demonstrate that the unique features of the Eger Rift subsurface environment provide the foundation for diverse types of microbial life, including the microbial utilization of geologically derived CO2 and when available H2, as a primary energy source.

microbiology↗