- 1Department of Environmental Geosciences, University of Vienna, Austria (veervikram49@gmail.com)
- 2Soil Chemistry, Wageningen University and Research, Netherlands (naresh.kumar@wur.nl)
- 3Department of Earth and Environmental Sciences, University of Manchester, United Kingdom (richard.kimber@manchester.ac.uk)
- 4Department of Evolutionary Anthropology, University of Vienna, Austria (ron.pinhasi@univie.ac.at)
Biopolymers, including nucleic acids, proteins, and carbohydrates, constitute a substantial fraction of soil organic matter (SOM). The adsorption of these biopolymers to mineral surfaces is widely regarded as a key protection mechanism against environmental decay, particularly from ubiquitous microbial enzymes, thereby facilitating long-term persistence.1 While extensive research has examined how the chemical composition governs organic matter adsorption and stability, the role of molecular size, particularly biopolymer length, remains poorly understood.2
Using DNA as a model biopolymer and minerals with diverse surface properties (goethite, ferrihydrite, kaolinite, montmorillonite, and hydroxyapatite), we investigated how polymer length affects both adsorption and protection against enzymatic decay. Results show that under competing conditions, shorter polymers exhibited preferential adsorption to all mineral surfaces. Furthermore, we examined enzymatic hydrolysis using DNase I as a model endonuclease. In solution, hydrolysis followed second-order kinetics with rate constants scaling linearly with the polymer length. Remarkably, while adsorbed DNA also showed length-dependent hydrolysis rates, hydrolysis ceased entirely for fragments below 50 base pairs—a threshold absent in solution.
This critical length threshold agrees very well with the median DNA polymer length observed across diverse environmental samples, providing experimental evidence for adsorption-driven enhanced protection of ultrashort biopolymers in soil and sediments.3,4 Our findings demonstrate that polymer length is a fundamental determinant of biopolymer persistence at mineral surfaces, with important implications for understanding MAOM stability. These results suggest that molecular properties, especially size and polymer length of organic matter, warrant greater consideration in SOM stabilization models and management strategies.
References
1. Kleber, M. et al. Dynamic interactions at the mineral–organic matter interface. Nat. Rev. Earth Environ. 2, 402–421 (2021).
2. Yu, W. H. et al. Adsorption of proteins and nucleic acids on clay minerals and their interactions: A review. Appl. Clay Sci. 80–81, 443–452 (2013).
3. Sawyer, S., Krause, J., Guschanski, K., Savolainen, V. & Pääbo, S. Temporal Patterns of Nucleotide Misincorporations and DNA Fragmentation in Ancient DNA. PLOS One 7, e34131 (2012).
4. Herzschuh, U. et al. Dynamic land-plant carbon sources in marine sediments inferred from ancient DNA. Commun. Earth Environ. 6, 78 (2025).
How to cite: Singh, V. V., Kumar, N., Kimber, R., Pinhasi, R., and Kraemer, S.: A Critical Length Threshold for Biopolymer Protection in Mineral-Associated Organic Matter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21244, https://doi.org/10.5194/egusphere-egu26-21244, 2026.
