9528168 Vollmer The general objective of this project is to investigate the interaction of intense ultrasound energy with Escherichia coli bacteria that have been genetically engineered to emit visible light (bioluminescence) when subjected to physical or chemical stress. Acoustic cavitation, the rapid growth and violent collapse of micro-sized bubbles in response to an impinging ultrasonic wave, is know to be responsible for damage to biological cells in vivo and in vitro. The high temperatures and pressures produced during radial bubble collapse can produce direct and chemically-mediated effects on nearby cells, or asymmetric bubble collapse can produce high-velocity microjets that puncture cellular membranes or bacterial walls. By systematically varying the acoustic parameters and by using particular promoter::lux fusions in genetically altered strains of E. Coli, this complex interaction will be better understood, allowing for an assessment to be made of the feasibility of applications such as ultrasonic water purification and intracorporeal sterilization of medical implants. The investigation during this twelve month award would follow a five step experimental protocol to test the hypothesis that ultrasound causes damage to bacterial membranes through the shear forces and free-radical production that accompany violent inertial cavitation of resonant microbubbles. The researches will use an heretofore unavailable acoustical detection system for cavitation together with a sensitive biological assay to quantify bacterial stress response (luminescence). The investigation is expected to provide an understanding of the bacterial stress-response due to the collapse of microbubbles undergoing transient cavitation that would help optimize the killing of bacteria and lead to improved sterilization procedures. ***
