Frequency-dependent ultrasound-induced transformation in E. coli

Development and mechanism exploration of a quantitative model for Escherichia coli transformation efficiency based on ultrasonic power

Ultrasonic-mediated plasmid transformation is a promising microbial transformation strategy with broad application prospects that has attracted interest across various fields. Limited research exists on developing a quantitative model to understand the relationship between transformation efficiency and ultrasonic power. Within the ultrasonic range that did not damage plasmids, the maximum transformation efficiency reached at 4.84 × 105 CFU/μg DNA. A kinetic model based on changes in membrane permeability was utilized to determine the membrane permeability at different power levels. The results indicated a linear correlation between ultrasonic power, transformation efficiency, and membrane permeability within a specific range. A quantitative relationship model was established based on ultrasonic power and transformation efficiency in E. coli. Electron microscopy revealed that E. coli cells subjected to ultrasonic treatment exhibited pore formation and cellular expansion. Furthermore, the integrity of the bacterial membrane was compromised as ultrasonic power increased. Nine genes associated with the functional terms of cell membrane components and transmembrane transport were identified in E. coli DH5α. According to qRT-PCR results, genes with these functions (including cusC, uidC, tolQ, tolA, ompC, yaiY) play crucial roles in ultrasound-mediated transformation of E. coli DH5α. This study suggested that ultrasound-mediated transformation in E. coli DH5α is not a simple physical-chemical process but rather involves the regulation of responsive membrane-related genes. This research establishes the groundwork for future comprehensive investigations into the molecular mechanism of ultrasound-mediated transformation and provides insights for the application of ultrasound technology in genetic engineering and related fields.

Review on low- and high-frequency sonolytic, sonophotolytic and sonophotochemical processes for inactivating pathogenic microorganisms in aqueous media

Ultraviolet and ultrasound-based advanced oxidation processes (AOPs) are gaining considerable research attention for water treatment and disinfection. Compared to low-frequency ultrasound (LFUS, <100 kHz), high-frequency ultrasound (HFUS, >100 kHz and MHz range) for water disinfection remains much less investigated. The present review aims at surveying and discussing literature data on microbial inactivation in non-food aqueous media using HFUS alone and with AOPs. More specifically, the review covers sonophotolytic (US/UV) processes under sequential and simultaneous modes as well as sonophotochemical processes, where both low and high frequencies were applied. Addressing a state-of-the-art biomedical research, we have attempted to provide more insight into mechanical and sonochemical mechanisms of inactivation under ultrasonic exposure. Sonoporation, intracellular generation of reactive oxygen species (ROS), energy stimulation of aquaporins to deliver ROS, and injection of extracellular ROS into sonoporated cells have all been identified as primary ways of inactivation. Application of ultrasound in the 0.2-2 MHz range and mercury-free light sources to support the Minamata Convention on Mercury is an ongoing challenge for effective elimination of microbial pathogens from water and wastewater through sonophotolytic and sonophotochemical AOPs.