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Proving lightning role in the evolution of life

2013; Elsevier BV; Volume: 10; Issue: 3 Linguagem: Inglês

10.1016/j.plrev.2013.07.026

1873-1457

Micaela Liberti, Francesca Apollonio, Caterina Merla, G. D’Inzeo,

Origins and Evolution of Life

The possible role of lightning in the evolution of life has been a greatly suggestive scientific theory since the times of the first ideas on the so-called “primordial soup” [1]. In his paper [2], T. Kotnik goes further and postulates that lightning could represent the source of energy able to initiate natural horizontal gene transfer (HGT) in bacteria, which integrate into their own chromosome foreign fragments of DNA by other species. The HGT, according to Kotnik’s hypothesis, can be mediated by the biophysical mechanism of membrane cell poration, known as electroporation or permeabilization [3]. Such an HGT process potentially accelerates the evolution since allows bacteria to acquire new physiological traits. However, the original experiment by Miller and Urey [1] in 1953 trying to prove the theory of the “primordial soup”, has been successively criticized because of the experimental conditions, considered not enough rigorous and realistic in reproducing the energy and the time course of the lightning [4]. Similarly here, to prove the HGT-lightning mediated hypothesis, maximally “sound designed” and controlled exposure conditions seem necessary, as suggested by the author himself. Indeed, in two recent studies of the group of Simonet [5,6] electrotransfer of plasmid DNA was achieved trying to maintain the similarity of the experimental conditions to those existing in nature. One important point is the necessity to test both theoretically and experimentally the hypothesis of a linear regime used to estimate the electric stimulation impacting on the bacteria cells. This hypothesis concerns both the radial, monotonic decrease of the electric field from the lightning impact point and the medium conductive behavior. A possible non-linear model of the medium conductive comportment could affect the precise evaluation of the radial distances and the maximum fields and temperature induced in the aqueous medium itself (see Eqs. (4) and (8) in [2]). Beside this item, a careful study of the propagation of the pulsed electromagnetic energy could be deepened in order to identify the limits of validity in disregarding the heat secondary effects. Moreover, to rule out the questions about the impact of bacteria wall on HGT, aroused by Kotnik [2], the use a microdosimetric approach [7–10] is recommended. This type of modeling is the only one able to clarify the actual