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.

KARINA K. SAND

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- Jun 28, 2021

Paper out: Did you ever wonder how cable bacteria transport electrons across decimeter distances?

Our study just published in Nature Communication show that long range conduction of cable bacteria is all in the chemical structure and electron transport mechanism of periplasmic bacterial wires.

Efficient long-range conduction in cable bacteria through nickel protein wires.

We combined high-resolution microscopy, spectroscopy, and chemical imaging on individual cable bacterium filaments and demonstrate that the periplasmic wires consist of a conductive protein core surrounded by an insulating shell layer.

The core proteins contain a sulfur-ligated nickel cofactor, and conductivity decreases when nickel is oxidized or selectively removed.

The involvement of nickel as the active metal in biological conduction suggests a hitherto unknown form of electron transport that enables efficient conduction in centimeter-long protein structures.

The nano-IR of the cables was tricky (and rewarding) to obtain, and I am amazed of the structures and capabilities of these bacteria.

Link: https://www.nature.com/articles/s41467-021-24312-4

Thanks lots to Eric for compiling all our data and leading the efforts. Is has been a highly inspirational journey.

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