Origin of lower-plant petroleum DNA sequences (oriDNA vs. environmental DNA)

Determine whether the lower-plant petroleum DNA sequences (including IDs ID_1G, ID_2G, and ID_3G that match Chlorophyta and Bryophyta) extracted from Nanyang Oilfield crude oil represent original in situ DNA from organisms that formed the Hetaoyuan Formation source rocks (oriDNA), post-depositional ancient environmental DNA (paeDNA), or recent/present environmental DNA (preDNA).

Background

The study reports eight lower-plant matches among petroleum DNA (pDNA), including Chlorophyta and Streptophyta/Bryophyta sequences. Several of these (ID_1G–ID_3G) appear distinct from known genomes and may be ancient DNA. However, many algae remain unsequenced and lower organisms can exhibit rapid genomic evolution, complicating taxonomic assignment and temporal origin inferences.

Because pDNA in reservoirs can include original in situ DNA (oriDNA), post-depositional ancient environmental DNA (paeDNA), and recent/present environmental DNA (preDNA), distinguishing the provenance class of these lower-plant fragments is necessary to interpret the biological sources of the Hetaoyuan Formation and to validate oil-source biogenic inferences.

References

With numerous unsequenced species of algae, it is currently not feasible to determine their specific species affiliation. Furthermore, the rapid evolution of genomes in lower organisms makes it difficult to determine if these sequences originated from ancient times. As a result, it remains uncertain whether they belong to oriDNA, paeDNA, or preDNA derived from post-source rock formation.

— DNA Fragments in Crude Oil Reveals Earth's Hidden History  (2412.06550 - Zhao et al., 2024) in Results and Discussion, (3) Explore local geological changes and species evolution