Bacterial cells were penetrated with chrysotile fibers and transformed to antibiotics resistance by incorporation of exogenous plasmid DNA

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A suspension of recipient E.coli cells in stationary phase, chrysotile asbestos, and pUC18 donor DNA was spread over the surface of an LB agar plate using a streak bar several times, resulted in intracellular uptake of the plasmid DNA by the E.coli cells. The transformation efficiency was highest with a duration of cell exposure to chrysotile for more than 60 seconds and a 2% agar concentration. To improve transformation efficiency by chrysotile mediation, we systematically optimized various conditions and parameters. In comparison to chrysotile exposure without cations, exposure with cations produced up to 100-fold more transformants. Optimized conditions resulted in 10^6 transformants per μg pUC18 DNA. The drastic physical change due to ‘quick drying on the surface of the agar plate', when cells were exposed to chrysotile, was essential for transformation by chrysotile mediation. We suggest that DNA uptake by chrysotile asbestos mediation is the result of a mechanical physical transformation of the E.coli, since E.coli cells are not competent chemically. Electron microscopy of cells exposed to chrysotile suggested penetration of the E.coli membrane by chrysotile fibers. It is suggested that E.coli transformation by the plasmid DNA was the result of penetration by chrysotile fibers to which plasmid DNA is bound or adsorbed.