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

将处于固定期的受体大肠杆菌细胞、温石棉和pUC18供体DNA的悬浮液用条纹条在LB琼脂板表面扩散几次，导致大肠杆菌细胞对质粒DNA的细胞内吸收。当细胞暴露在温石棉中超过60秒，琼脂浓度为2%时，转化效率最高。为了提高温石棉催化转化效率，系统地优化了各种条件和参数。与不含阳离子的温石棉暴露相比，含阳离子的温石棉暴露产生的相变多出100倍。优化后的条件下，每μg pUC18 DNA产生10^6个转化子。当细胞暴露于温石棉时，由于“琼脂板表面快速干燥”而发生的剧烈物理变化对于温石棉介导的转化是必不可少的。我们认为，温石棉介导的DNA摄取是大肠杆菌机械物理转化的结果，因为大肠杆菌细胞在化学上是不称职的。接触温石棉的细胞的电子显微镜显示，温石棉纤维可以穿透大肠杆菌膜。这表明，大肠杆菌被质粒DNA转化是质粒DNA与温石棉纤维结合或吸附的结果。

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.