Heat treatments are widely used by the food industry to inactivate microorganisms, however their mode of action on microbial cells is not fully known. In the last years, it has been proposed that the generation of oxidative species could be an important factor contributing to cell death by heat and by other stresses; however, investigations in this field are scarce. The present work studies the generation of reactive oxygen species (ROS) upon heat treatment in E. coli, through the use of cell staining with specific fluorochromes. Results obtained demonstrate that ROS are detected in E. coli cells when they are subjected to heat exposure, and the amount of fluorescence increases with temperature and time, as does the cellular inactivation. The addition of glutathione or tiron, a potent antioxidant and a superoxide quencher, respectively, to the heating medium protected E. coli against heat inactivation and concurrently reduced the detection of ROS, especially in the case of glutathione. Finally, recovery of heated cells under conditions that relief oxidative stress produced an increase in cell survival. Data presented in this work support the view that ROS generation and subsequent control in bacterial cells could be an essential factor determining inactivation and survival upon exposure to heat, and it could be a potential target to increase the efficacy of current treatments.

the pole of the S, C or C' planes and k max axes are parallel to the transport direction and related to ductile S-C structures. Furthermore, the Pj-T changes across the shear zone characterize strain variations: larger Pj and T are found in the basal, most deformed part of the shear zone, and lower values are found where the interaction between Alpine and Variscan-related petrofabrics is stronger. We also interpret the reactivation of Variscan inherited fabrics within the Alpine shear zone. In spite of the heterogeneous strain, markers indicate a common, top-to-the-South (N190E) Alpine transport direction, which contrasts with the strong obliquity of the genetically-related structures developed in the Southern Mesozoic sedimentary cover. In this sense, our data suggest a complete decoupling between basement and cover units during the Alpine compression.

Large-scale faults in the continental crust are significant features that control the evolution of sedimentary basins and intraplate mountain chains. Deciphering their evolution is a significant task because faults slip and reactivate in a variety of geological settings. In this work, clay gouges of two major orogen-scale, long-lived faults in northern Iberia, the Río Grío and Vallès-Penedès Faults, were investigated by X-ray diffraction and K-Ar isotopic analysis. Illite polytype determinations of 44 subfractions (from <0.1 to 10 μm) allowed us to discriminate between authigenic/synkinematic illite crystals formed during faulting and detrital illite crystals inherited from the host rock. K-Ar dating provided a detailed set of ages corresponding to key stages of the thermotectonic evolution of the Iberian Plate: (a) the Permian to Late Triassic extensional/transtensional activity associated to the emplacement of Late Variscan magmatic bodies and hydrothermal mineralizations, (b) the opening of the Central Atlantic Rift during Late Triassic-Early Jurassic times, (c) the Late Jurassic-Early Cretaceous rifting that led to the development of Mesozoic extensional/transtensional basins in northern Iberia, (d) the final stage of the anticlockwise rotation of the Iberian Plate with respect to Eurasia and the accommodation of the first Pyrenean compressional pulses in Campanian time, and (e) the positive inversion of Mesozoic extensional basins due to far-field stresses associated with the Alpine orogeny during the Paleogene. The results highlight that thermotectonic conditions characterized by high-geothermal gradients strongly favor fault movement and neoformation of clay minerals in fault gouges, regardless of the prevailing tectonic regime.

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