Development and applications of a DNA labeling method with magnetic nanoparticles to study the role of horizontal gene transfer events between bacteria in soil pollutant bioremediation processes.

Horizontal gene transfers are critical mechanisms of bacterial evolution and adaptation that are involved to a significant level in the degradation of toxic molecules such as xenobiotic pesticides. However, understanding how these mechanisms are regulated in situ and how they could be used by man to increase the degradation potential of soil microbes is compromised by conceptual and technical limitations. This includes the physical and chemical complexity and heterogeneity in such environments leading to an extreme bacterial taxonomical diversity and a strong redundancy of genes and functions.

Magnetic nanoparticle DNA labeling for individual bacterial cell detection and recovery.

A culture independent approach was developed for recovering individual bacterial cells out of communities from complex environments including soils and sediments where autofluorescent contaminants hinder the use of fluorescence based techniques. For that purpose fifty nanometer sized streptavidin-coated superparamagnetic nanoparticles were used to chemically bond biotin-functionalized plasmid DNA molecules. We show that micromagnets can efficiently trap magnetically labeled transformed Escherichia coli cells after these bacteria were subjected to electro-transformation by these nanoparticle-labeled plasmids.