DISTRIBUTION OF ANTIBIOTIC RESISTANCE GENES IN THE ENVIRONMENT:
THE ROLE OF MINERAL FACILITATED HORIZONTAL GENE TRANSFER
Combining recent research across disciplines, I see evidence 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.
Bacterial colony formation.
Image by Lisselotte Jauffred (collaborator from NBI)
The spread of antibiotic resistance genes (ARg) is a worldwide health risk1 and is no longer only a clinical issue. Vast reservoirs of ARg are found in natural environments2–4 such as soils, sediments and oceans. The emergence and release of ARg to the environment is in particular caused by extended use of antibiotics in farming, e.g. where the genes dissipate from the manure.5 Once in the environment, the ARg are surprisingly rapidly propagated. It is well known that the ARg are distributed to neighbour bacteria through processes of both cell sharing or through horizontal gene transfer (HGT) where one species acquirer resistance from another.6,7 Most HGT responsible for the spread of ARg are assumed to be through direct microbe-microbe contact. However, I find that the outcome of non-contact transfer is grossly underestimated. In the HGT mechanism called “Transformation”, free ARg in suspension or adsorbed to a mineral can be picked up and incorporated into non-related organisms. Considering that free DNA only can survive for a few weeks in sea- and freshwater environments,8–10 any HGT from free DNA can rightly be assumed to be local, but if the DNA gets adsorbed to a mineral, it can survive for several hundred thousands of years.11–14 If this also holds for ARg, then minerals offer a potent mechanism for distributing ARg through our environments my means of sedimentary processes.
THE PROTEIN ARCHIVE
Preservation potential of ancient human diets and diseases
DNA and proteins are now almost routinely being retrieved from sediments and archaeological artefacts. Despite the realization that adsorption of DNA molecules onto the surfaces of minerals can significantly decrease the DNA and protein decay rate, the longevity of mineral bound biomolecules is a still-standing frontier. Recently it was shown that peptide sequences in eggshell proteins persist to 3.8 Ma in Africa, implying that protein sequences will span the whole of human history in all parts of the world. Ancient protein sequences, therefore, persist beyond the lipid or DNA sequence and can be used to identify organisms (ZooMS), identify specific tissues, sex individuals, and identify tissue responses to disease.
Understanding the protein-mineral interaction and environmental preservative conditions of adsorbed biomolecules –proteins can thus allow us to a) target such environments for paleoecological and palaeogenetic studies and; b) serve as a quantitative tool for assessing protein sequence migration i.e. ancient microbial communities. To date, we only have a qualitative idea of how solution composition affects the protein-mineral adsorption/desorption at the bulk level, and we have no quantitative insight into the single bond level energetics as well as the nature and fraction of the interacting bonds.
Project collaborator: Prof. Matthew Collins, GLOBE and Cambridge, UK.
FUNDING
HORIZON 2020
Toosin a Marie Skłodowska-Curie Individual Fellowship (H2020-MSCA-IF-EF-ST) for our ProArch project.
APPROACH
We are currently combining top down and bottom up approaches to address these questions
Updates on progress and ongoing data collection in the Blog
Near-final and Published data will be added below
Stay tuned
