| To explore the mechanism of natural population’s adaptation and resistance toenvironmental conditions, especially the reaction of microorganisms to variousenvironmental factors has come into focus in the fields of modern microbial ecologyand molecular ecology. Audible sound wave, frequency between20~2×10~4Hz, waswidespread in nature. It is an important environmental factor. Facing the increasinglyserious problem of acoustic pollution, very little efforts have been put forth in studyingthe relation of single cell organisms and sound field. So it is vitally significant toexplain the adjustment and adaptation mechanism of organisms includingmicroorganism in acoustic environment by studying the microbial effect of soundenvironment stress, exploring the effect of different sonic exposure dose, revealing thepathways and molecular mechanism; It also has a positive guidance on the reasonabledevelopment and use of sound effect, helping to explore and set up a risk assessmentand early warning system in acoustic environment based on single-celled organisms,developing a new biological technology based on the acceleration of the effect ofsound in terms of growth, metabolism and synthesis.In this paper, a sound wave load apparatus was designed and we attempted to usethe single-cell model organism Escherichia coli to investigate the physiological andecological effects of audible sound waves stimulation in liquid culture. Meanwhile,study on calcium’s role in E.coli response to sound stimulation mechanisms was alsoexplored. The main contents and conclusions are as follows:Firstly, to investigate the response of E. coli to sound field exposure, the E. coligrowth behavior and the production situation of the induced molecular AI-2werestudied in liquid culture, which was exposed to sound wave. The results showed thatthe adjustment of the sound intensity in fixed frequency could affect the growth of E.coli, which appeared as a kind of nonlinear state, characterized by a certainfrequency and intensity of window dependence, and it was same with that of thefrequency in fixed sound intensity; When exposed to the noise intensity of100dB andfrequency of5000Hz, this effect could make a very obvious phenomenon of growthpromoting. at the same time, by monitoring the secretion of the induced molecular AI-2, it indicated that the sound field exposure could significantly affected the synthesisand secretion of the AI-2molecule in bacteria, and possibly through some passivationmechanism of quorum sensing system, so as to make the same nutrition conditionpresent a bacteria population density threshold differences.Secondly, the physiological effects of sound field exposure of E. coli wereexplored. The results demonstrate that acoustic environmental exposure could increasethe total intracellular protein content significantly and change the ATP enzyme activityvisibly; in the meantime, the change of intracellular SOD and CAT enzyme activities,and the monitoring of the wave of MDA content demonstrated that the acousticenvironmental exposure might induce intracellular secondary oxidative stress effect.Thirdly, calcium signal is considered to be an early event of organism responsingto mechanical stimulation, so it plays an important role in understanding and torevealing the changes of calcium signals in microorganism in stress response that theanalysis of the concentration of the intracellular calcium ion of E. coli exposed tosound field exposure. Studies have found that sound field exposure may change theintracellular calcium ion concentration by affecting the cell membrane channel state,and concentration change is associated with the frequency and intensity of sound fieldexposure. At the same time, the mechanical sensible ion channel and calcium channelplay a certain role in flowing mediated calcium, and the latter plays a moreimportment role. |
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