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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.

bug colony.png

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.

KKS

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- Dec 23, 2023

Featured at ACS Central Science : "This molecular biogeochemist investigates how minerals preserve DNA and affect evolution"

During October Science Journalist Carolyn Wilke has been interviewing me about my research interests and approaches to address DNA preservation in sediments and mineral facilitated evolution of life. The piece will be followed by an extended version in Chemical & Engineering news as a Q&A in 2024.

Carolyn's interest in my work began with the 2 Ma DNA recovered from the Kap København formation and we talked about how our work on DNA-minerals contributed to the study. From there on we talked about the perspectives of using ancient environmental DNA. We also talked about my groups work on how the interplay between DNA and minerals and bacteria can influence bacterial evolution.

I have not been able to check the piece before it is published so it is great to see it finally. I am super excited t about this opportunity to showcase how nano-level dynamics can pave the way for a mechanistic understanding on taphonomy of ancient environmental DNA and how interfacial geochemistry is essential for many fields.

ACS central Science piece here: https://pubs.acs.org/doi/10.1021/acscentsci.3c01574

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