A Research On The Effects Of Audible Sound Stimulation On The Growth And Metabolism Of Escherichia Coli And Its Mechanism

Audible sound, one of the environmental factors, widely exists in natural world. However, the interaction between audible sound and biological materials is usually neglected in the field of biological research. Very little efforts have been put forth in studying the relation of organisms and audible sound. The research has positive significance for us to get more information about audible sound wave biological effects and reveal its underlying mechanism.In this paper, a sound wave load apparatus was designed, and then we investigated the biological effects of audible sound on E.coli growth, physiological characteristics and the structure of cell membrane. Meanwhile, the potential role of calcium signaling in mediating the response of E.coli to audible sound was primarily discussed. The main research contents and results are as follows:Firstly, the basic law of effects of audible sound stimulation on E.coli growth was investigated. The results showed that the audible sound field stimulation can significantly affect E.coli growth and metabolic action, which can enhance or inhibit the growth of E.coli, and the promotion effects of sound field on E.coli depended greatly on the intensity and frequency of audible sound. The optimal stimulation conditions are 100 dB and 1000 Hz. Under the conditions, the sound field can distinctly enhance the growth of E.coli cells. However, under osmotic stress induced by the sugar, audible sound stimulation may enhance the inhibitory effect of osmotic stress on E. coli growth. More interestingly, audible sound treatment seems to alleviate the inhibitory effect of salt stress on E.coli growth. Some potential mechanisms may be involved in the responses of bacterial cells to audible sound stimulation.Secondly, under certain frequency and the intensity, the stimulated groups would get obvious increasing in the contents of intracellular protein by contrast with the control groups, on average by 59.5%, and the activities of SOD and CAT elevated by 68.56% and 14.4% respectively, indicating that audible sound waves with a certain intensity and frequency increased the metabolic activity of cells.Thirdly, the effects of audible sound wave on membrane structure and function was studied. The results demonstrate that audible sound increases the penetration activity of cell membrane under the condition of not hurting cells. At the same time, the fourier transform infrared spectroscopy was employed to study the effect of audible sound stimulation on the amideâ… ,â…¡and amideâ…¢of plasmalemma protein. The results indicate that audible sound wave stimulation has changed the secondary structure of plasmalemma protein.In addition, the role of calcium signaling in mediating the response of E.coli to audible sound stimulation was studied. We found the lack of calcium ion in medium significantly alleviated audible sound wave biological effects, and audible sound wave stimulation could evidently enhance total intracellular Ca²⁺ content.