Electrooptics studies of Escherichia coli electropulsation: orientation, permeabilization, and gene transfer.
Fast optical transient signals are suitable approaches to the investigation of the behavior of bacteria during an electric pulse. In a previous work, by a dual approach taking advantage of a video method and a fast kinetic study of the light transmitted across a cell suspension, we showed that a field-induced orientation phenomenon was affecting the rod-shaped bacteria during the pulse (Eynard et al., 1992. Eur. J. Biochem. 209:431-436). In the present work, time courses of electro-induced responses of bacteria during a single square-wave pulse are analyzed. Observations of both the orientation step and the permeabilization process are relevant. These two steps are affected by the addition of DNA. They both obey to a first-order kinetic. The conclusion of this work is that Escherichia coli permeabilization and transformation are multistep processes: orientation (step 1) is followed by an envelope alteration (step 2), all steps being affected by plasmid addition. In the case of E. coli, a rod-shaped bacteria, the orientation process (step 1) brings the cell parallel to the field direction. The pulse duration must be longer than the orientation characteristic time (approximately 1 ms) to trigger an effective permeabilization and its associated events. The permeabilization process (step 2) is associated with a field-induced dipole effect.
Eynard
N
N
IPBS-CNRS, UPR 9062, 31062 Toulouse cedex, France.
Rodriguez
F
F
Trotard
J
J
Teissié
J
J
D002463:Cell Membrane Permeability / Q000502:physiology; D004247:DNA / Q000235:genetics; D018274:Electroporation / Q000379:methods*; D004926:Escherichia coli / Q000378:metabolism*; D018014:Gene Transfer Techniques; D007700:Kinetics; D008027:Light; D018715:Microscopy, Video; D009391:Nephelometry and Turbidimetry; D010957:Plasmids / Q000235:genetics; D014162:Transfection / Q000235:genetics
D004247:DNA