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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.

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

- Oct 29, 2021

Congratulations Dr. Sam Armistead!

Today I had the pleasure of examining Sam on his Viva on Biopolymer stabilization of soils.

Sam has been developing a high throughput micro-macro approach for characterizing biopolymer stabilization in mine tailing soils. His results are a beautiful example of how interfacial interactions between biopolymers, mineral surfaces and solutions drive micro- and macro- scale properties and observations.

Tony and I made our best efforts to challenge Sam on his understanding of the system and in how to make it applicable for natural systems. Sam was well prepared and we had an almost 2 hr long constructive (and interesting) discussion. Thanks for the opportunity to pick your brain and for reading your Viva- there is a lot of food for thought in there. And it was nice to learn some civil engineering on the way.

Best of luck in Sweden and I hope our paths cross again!

Congratulations Dr. Sam Armistead!

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