For example, Ugarte-Romero et al. (2006) investigated the effects
of ultrasound treatments on the morphology of E. coli K12
using environmental scanning electron microscopy (ESEM). They
observed that sonication at 40 °C for 3 min caused significant changes
in cell morphology (Fig. 2c) compared to control cells (Fig. 2a) or
heat alone treatment at 40 °C for 3 min (Fig. 2b). Sonication induced
pitting on the cell surface, which can be a result of high velocity
microjets generated during the collapse of cavitation bubble. Disruption
of the cellular structure and functional components of microbial cells
lead to cell lysis. Other possible mechanisms are associated with
the localized heating (5500 °C), high pressure (500 MPa) and formation
of free radicals (H+, O−, OH−, HO2
− and H2O2), which results from the
sonolysis of water present in liquids