Pradhan Hemanta, Poudel Arpan, Shrestha Diksha, Rogers Ariel, Stewart Michael, Jereb Amani, Harper Jack, Li Ming, Zhang Wen, Chen Jingyi, Wang Yong
Department of Physics, University of Arkansas, Fayetteville, Arkansas, 72701, USA.
Department of Electrical Engineering and Computer Science, University of Arkansas, Fayetteville, Arkansas, 72701, USA.
Eur Phys J E Soft Matter. 2025 Sep 15;48(8-9):56. doi: 10.1140/epje/s10189-025-00521-3.
Elevated levels of silver in aquatic environments arising from widespread use of silver nitrate and silver nanoparticles in different sectors of industry and medicine pose significant biophysical challenges to aquatic microorganisms. Despite extensive toxicity studies of silver on bacteria and microbial communities, its influence on other aquatic microorganisms, such as microalgae, remains poorly understood. In this study, we investigated the biophysical response of C. reinhardtii microalgae to silver ion exposure in terms of their population growth dynamics, chlorophyll content, and swimming motility. We found that silver ions at different concentrations (from 0.29 to 1.18 M) elongated the lag phase of the microalgal growth. However, the growth of the microalgae was boosted by silver ions at low concentrations (e.g., 0.29 M), showing higher OD values at the stationary phase and higher maximum growth rates. This hormetic response exhibited by microalgae upon exposure to silver ions indicates a nonlinear coupling between ionic stress and cellular growth. Additionally, we quantified the chlorophyll content in the microalgae with different concentrations of silver ions using spectrophotometric analysis, which revealed that the microalgae cells contained twice as high concentrations of chlorophyll when exposed to silver ions at lower concentrations. More importantly, we monitored the motion of microalgae in the presence of silver ions, detected and tracked their motion using a deep learning algorithm, and determined the effects of silver ions on the swimming motility of individual C. reinhardtii microalgae. Our results showed reduced average swimming speed and increased directional change of microalgae upon silver ion exposure.
由于硝酸银和银纳米颗粒在工业和医药等不同领域的广泛使用，导致水生环境中银含量升高，这给水生微生物带来了重大的生物物理挑战。尽管对银对细菌和微生物群落的毒性进行了广泛研究，但其对其他水生微生物（如微藻）的影响仍知之甚少。在本研究中，我们从莱茵衣藻微藻的种群生长动态、叶绿素含量和游动能力方面，研究了其对银离子暴露的生物物理反应。我们发现，不同浓度（0.29至1.18 M）的银离子延长了微藻生长的滞后期。然而，低浓度（如0.29 M）的银离子促进了微藻的生长，在稳定期显示出更高的OD值和更高的最大生长速率。微藻暴露于银离子时表现出的这种 hormetic 反应表明离子应激与细胞生长之间存在非线性耦合。此外，我们使用分光光度分析对不同浓度银离子处理下的微藻叶绿素含量进行了量化，结果显示，在较低浓度银离子处理下，微藻细胞中的叶绿素浓度高出两倍。更重要的是，我们监测了银离子存在下微藻的运动，使用深度学习算法检测和跟踪它们的运动，并确定了银离子对单个莱茵衣藻微藻游动能力的影响。我们的结果表明，银离子暴露后微藻的平均游动速度降低，方向变化增加。
