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. Among other applications, this method could extend the range of approaches developed to study DNA dissemination among environmental bacteria without requiring cultivability of recombinant strains or expression of heterologous genes in the new hosts.