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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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- Mar 17, 2023

Preprint out: Advance your ecological inference using mineralogy and interfacial geochemistry

I know! Mineralogy and interfacial geochemistry rock!

They rarely get the attention they deserve though.

In our new preprint we show how principles of mineralogy and interfacial geochemistry can be applied to advance interpretations of eDNA and SedaDNA. We use the ~2.0 Ma old Kap København deposit as a case study and show how we can use quantitative mineral analysis and DNA adsorption isotherms to assess eDNA provenance and the potential of its preservation in sediments. If you are still interested after reading that very long sentence I solute your dedication. It is quite an entertaining study though, if I may say so. It also includes AFM images showing how DNA prefers to associate with certain adsorption sites over others. You will also find distribution coefficients that show how mineral loading in a suspension influence retention of extracellular DNA! Do not forget though to pay attention to the schematics in Fig. 5 next time you subsample or are in the process of inferring your eDNA data: Sediment provenance, retention and DNA taphonomy matters!

A pretty picture that has noting as such to do with the study. I intend for it to make you reflect on sediment provenance and DNA taphonomy in the environment.

Thanks heaps to

coauthors : Stanislav Jelavić, Kurt Kjær and Ana Prohaska.

&

VILLUM FONDEN

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