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.

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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

KARINA K. SAND

LEKTOR / ASSOCIATE PROFESSOR

MOLECULAR GEOBIOLOGY

Bio-mineral interactions

I am an experimentalist with a geology and geochemistry background. In my group we apply in-situ molecular- to macro scale techniques to study bio-mineral interactions to improve our understanding on these topics.

Interactions between organic molecules and mineral surfaces have a range of interesting aspects. They are vital for many forms of life and essential for both organizing shell structures and for anchoring an organism to a substrate. Bio-mineral interactions can also reveal traces of past life and be controlling for large and smaller scale mineralization and have a significant influence on element cycles. Additionally, such interactions could have enhanced the RNA polymerization needed for the origin of life. Recently I have found evidence to support that interactions between DNA and minerals could have a significant contribution to the evolution of life and propagation of antibiotic resistance genes through mineral facilitated horizontal gene transfer.

I am working with microbes, biomolecules (polysaccharides, DNA, EPS), model molecules (thiol chemistry, peptoids) and a range of different minerals (clays, CaCO3, iron oxides, quartz...)

PROJECTS

Antibiotic resistance

(incl. examples for student projects)

Evolution of life

(incl. examples for student projects)

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Student projects

Preservation of eDNA

(incl. examples for student projects)

Bacteria

Carbonate particles

Tuning CaCO3 mineralisation

Origin of life

Quantification of molecular binding

Biomineralization

C turnover and BIF

Polymeric control of CaCO3

Calcite growth and inhibition

Nucleation and growth

Shape and form

Mineral exploration

Bacteria

Iron oxide

partcles

Bacterial control

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