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Mineral facilitated horizontal gene transfer in the Molecular Geobiology Group
The Geobiology Group investigates whether interactions between DNA and minerals could have had a significant contribution to the evolution of life, by combining nanoscale bottom-up approaches with bulk techniques, microbiology and fieldwork. The group essentially aim to test the hypothesis of mineral facilitated evolution of life and implications for the rapid propagation of antibiotic resistance genes in our environments.
We use atomic force microscopy in 3 different modes: imaging, fast scanning and force and supplement the results with in-situ surface sensitive FTIR to investigate dynamics of DNA-mineral interactions in different environmental conditions. We combine the nanoscale results with approaches from different disciplines such as geology, microbiology, geochemistry, molecular biology and physics. Our cross-disciplinary approach allows us to tackle our research questions from many angles and we can thoroughly access the interplay between microbes, minerals and DNA and how it influences the propagation of genetic traits into the environments as a function of geologic setting.
Subproject 1: Propagation of antibiotic resistance genes (ARg) in
We find that minerals hold a high and unrecognized potential for enhancing the distribution of the ARg in the environment. Adsorption of ARg to minerals significantly increases the ARg’s lifetime and facilitates their distribution by sedimentary transport processes. In addition, minerals also serve as a) sites for horizontal gene transfer (HGT), b) platforms for microbial growth and, hence 3) act as hot spots for propagation of adsorbed ARg to other microbes. However, some minerals and ARg are bound more strongly than others and various bacteria have different affinities toward various minerals. Those variations in affinity are poorly quantified but vital for predicting the distribution of ARg in the environment.
VILLUM Young Investigator grant
Subproject 2: Biomimicry of composite materials.
Mimicking the properties of, e.g., nacre has received great attention because the mixture of brittle CaCO3 platelets and elastic biopolymers offer strong material properties. Tunable Peptoid peptoid polymers show promise for acting as the “soft elastic parts” in composites materials and have been recognized to stabilize CaCO3 during non-steady state crystallization. We are looking into the kinetic and thermodynamics driving forces of CaCO3 mineralization in order to upscale the mineralization process in a controlled manner.
Subproject 3: Stability of milk protein
Dental calculus (tartar, bioapatite) is often regarded as the most complete source of historical data, especially for probing: a) ancient microbial communities, b) ancient diets, and c) human- environment interaction. It has therefore been a surprise that whey protein β-lactoglobulin (BLG) is typically the only protein preserved in ancient dental calculus (apatite?), whereas lime-scal (calcite) from ceramics show preservation of a much richer mixture of milk (and food) proteins. The paucity of milk proteins on calculus contrasted with their comparative abundance of ceramics
implies selective differences in incorporation or preservation. We are currently using a bottom up approach combined with molecular dynamic simulation studies to understand the different binding mechanisms in play in this system and how this will influence the longevity of the proteins in the two different systems.
Horizon 2020 COFUND
Subproject 4: Fragmentation of DNA in sediments
Traces of nuclear, mitochondrial or chloroplast DNA can be released into the environment through faeces, urine or decomposition of dead organisms. Such environmental DNA (eDNA) can provide valuable information on past and present organisms. Recovering eDNA can be difficult as biotic (e.g. microbial attack) and/or abiotic (e.g. pH, temperature, hydrolysis) factors can lead to its partial or complete destruction. Despite the realisation that adsorption of DNA molecules onto the surfaces of minerals can significantly decrease the DNA decay rate and process, the longevity of mineral bound DNA is still unknown. The process of decay is important for understanding the preservation potential of mineral bound DNA. We are working to figure out how the substrate topography and charge density affect fragmentation of DNA.
Horizon 2020, MSCA-IF
Sand, K.K. & Jelavić, S. 2018. Minerals holds a high potential for distributing genetic traits across time and space and serve as platforms for facilitating horizontal gene transfer. Frontiers in Microbiology,
Freeman,. et al. 2020. The DNA-mineral stability is a function of environmental conditions and mineralogy. BioRxiv.
Sand, K.K. 2017. Application of dynamic force spectroscopy for obtaining quantitative bond parameters between polymers and minerals. Scientific reports.
List of publications by Karina Krarup Sand.
Danish Council for independent research: