To explore engineering platforms towards ‘active bacterial baths’, we grow and characterize native and commercial strains of Acidithiobacillus ferrooxidans to promote swimming locomotion. Three different energy sources were used, namely elemental sulfur, ferrous sulfate, and pyrite. The characteristics of the culture, such as pH, Eh, and the concentration of cells and ions, are monitored to seek correlations between the oxidation route and the transport mechanism. We found that only elemental sulfur induces swimming mobility in the commercial DSMZ – 24,419 strain, while ferrous sulfate and the sulfide mineral, pyrite, did not activate swimming on any strain. The bacterial mean squared displacement and the mean velocity are measured to provide a quantitative description of the bacterial mobility. We found that, even if the A. ferrooxidans strain is grown in a sulfur-rich environment, it preferentially oxidizes iron when an iron-based material is included in the media. Similar to other species, once the culture pH decreases below 1.2, the active locomotion is inhibited. The engineering control and activation of swimming in bacterial cultures offer fertile grounds towards applications of active suspensions such as energy-efficient bioleaching, mixing, drug delivery, and bio-sensing.

中文翻译：

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含氧化亚铁硫杆菌的活性流体：游泳与氧化途径之间的相关性

为了探索“活性细菌浴”的工程平台，我们培养和表征氧化亚铁硫杆菌的天然和商业菌株，以促进游泳运动。使用了三种不同的能源，即元素硫、硫酸亚铁和黄铁矿。监测培养物的特性，例如 pH、Eh 以及细胞和离子的浓度，以寻找氧化途径与转运机制之间的相关性。我们发现，在商业 DSMZ – 24,419 菌株中，只有元素硫诱导游泳活动，而硫酸亚铁和硫化物矿物黄铁矿不会激活任何菌株的游泳活动。测量细菌均方位移和平均速度以提供细菌流动性的定量描述。我们发现，即使 A. ferrooxidans 菌株在富含硫的环境中生长，当培养基中包含铁基材料时，它优先氧化铁。与其他物种类似，一旦培养物 pH 值降至 1.2 以下，主动运动就会受到抑制。细菌培养中游泳的工程控制和激活为活性悬浮液的应用提供了肥沃的土壤，例如节能生物浸出、混合、药物输送和生物传感。