School of Biological Sciences, University of Auckland, Auckland CBD, New Zealand, New Zealand.
Department of Food Science, University of Otago, Dunedin, New Zealand.
PLoS One. 2023 Feb 17;18(2):e0281762. doi: 10.1371/journal.pone.0281762. eCollection 2023.
Sound is a physical stimulus that has the potential to affect various growth parameters of microorganisms. However, the effects of audible sound on microbes reported in the literature are inconsistent. Most published studies involve transmitting sound from external speakers through air toward liquid cultures of the microorganisms. However, the density differential between air and liquid culture could greatly alter the sound characteristics to which the microorganisms are exposed. In this study we apply white noise sound in a highly controlled experimental system that we previously established for transmitting sound underwater directly into liquid cultures to examine the effects of two key sound parameters, frequency and intensity, on the fermentation performance of a commercial Saccharomyces cerevisiae ale yeast growing in a maltose minimal medium. We performed these experiments in an anechoic chamber to minimise extraneous sound, and find little consistent effect of either sound frequency or intensity on the growth rate, maltose consumption, or ethanol production of this yeast strain. These results, while in contrast to those reported in most published studies, are consistent with our previous study showing that direct underwater exposure to white noise sound has little impact on S. cerevisiae volatile production and sugar utilization in beer medium. Thus, our results suggest the possibility that reported microorganism responses to sound may be an artefact associated with applying sound to cultures externally via transmission through air.
声音是一种物理刺激，有可能影响微生物的各种生长参数。然而，文献中报道的可听声音对微生物的影响并不一致。大多数已发表的研究涉及通过空气向微生物的液体培养物传播来自外部扬声器的声音。然而，空气和液体培养物之间的密度差异可能会极大地改变微生物所接触到的声音特征。在这项研究中，我们应用白噪声声音在一个高度受控的实验系统中，我们之前建立了用于将声音直接传送到水下液体培养物中，以研究两个关键的声音参数，频率和强度，对商业酿酒酵母在麦芽糖最小培养基中生长的发酵性能的影响。我们在消声室中进行了这些实验，以最小化外部声音，并发现声音频率或强度对该酵母菌株的生长速率、麦芽糖消耗或乙醇生产几乎没有一致的影响。这些结果与大多数已发表的研究报告的结果相反，与我们之前的研究结果一致，表明酵母直接暴露于水下白噪声对啤酒培养基中酵母挥发性物质的产生和糖的利用影响很小。因此，我们的结果表明，报道的微生物对声音的反应可能是通过空气传播将声音应用于培养物的外部的一种人为产物。
