A pilot study of the effect of audible sound on the growth of Escherichia coli

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. Here we investigated the response of Escherichia coli cells to the stimulation by audible sound under the normal condition and environmental stresses. The results showed that the audible sound treatment significantly increases the colony forming of E. coli under the normal growth condition. 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 when the concentration of sodium chloride was increased to 30 g/l, although the action of sound waves of audible frequency is likely to evoke an inhibition of the growth of E. coli in the medium containing 20 g/l of sodium chloride. Some potential mechanisms may be involved in the responses of bacterial cells to audible sound stimulation.