Emulating Exposures of Biological Samples to Lightning Strokes

We developed a generator for controlled exposure of small biological samples to conditions they experience when lightnings strike their habitats. We tested the generator with our exposure chamber described previously. Recording at 341 thousand frames per second with Vision Research Phantom® v2010, the fastest commercially available camera, we found that the initial arc descended vertically into the sample, but then became accompanied by arcs descending increasingly sideways; after 8–12 μs, as the first of these arcs formed direct contact with the receiving electrode. We eliminated this artefact by a Plexiglas® cylinder positioned concentrically between the electrodes. While bacterial spores are highly resistant to electric pulses delivered through direct contact, we show that with discharges delivered as arcs through an air gap and thus accompanied by acoustic shock wave, spore inactivation is readily obtained.