Uemura Naoki A, Chiba Naoya, Morikawa Ryota, Tamakoshi Masatada, Nakane Daisuke
Department of Engineering Science, The University of Electro-Communications, Chofu City, Tokyo 182-8585, Japan.
School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji City, Tokyo 192-0392, Japan.
ISME J. 2025 Jan 2;19(1). doi: 10.1093/ismejo/wraf164.
Bacteria thrive in nearly all environments on Earth, demonstrating remarkable adaptability to physical stimuli, as well as chemicals and light. However, the mechanisms by which bacteria locate and settle in ecological niches optimal for their growth remains poorly understood. Here, we show that Thermus thermophilus, a highly thermophilic non-flagellated species of bacteria, exhibits positive rheotaxis, navigating upstream in unidirectional rapid water flow. Mimicking their natural habitat at 70°C with a water current under optical microscopy, cells traveled distances up to 1 mm in 30 min, with infrequent directional changes. This long-distance surface migration is driven by type IV pili, facilitating vertical attachment at the cell pole, and shear-induced tilting of the cell body, resulting in alignment of the leading pole toward the direction of water flow. Direct visualization of type IV pili filaments and their dynamics revealed that rheotaxis is triggered by weakened attachment at the cell pole, regulated by ATPase activity, which was further validated by mathematical modeling. Flow experiments on 15 bacterial strains and species in the Deinococcota (synonym Deinococcus Thermus) phylum revealed that positive rheotaxis is highly conserved among rod-shaped Thermaceae, but absent in spherical-shaped Deinococcus. Our findings suggest that thermophilic bacteria reach their ecological niches by responding to the physical stimulus of rapid water flow, a ubiquitous feature in hot spring environments. This study highlights unforeseen survival strategies, showcasing an evolutionary adaptation to a surface-associated lifestyle where swimming bacteria would otherwise be swept away.
细菌在地球上几乎所有环境中都能茁壮成长，对物理刺激、化学物质和光线表现出非凡的适应性。然而，细菌如何定位并在最适合其生长的生态位中定殖的机制仍知之甚少。在此，我们表明嗜热栖热菌，一种高度嗜热的无鞭毛细菌物种，表现出正向趋流性，在单向快速水流中向上游游动。在光学显微镜下用一股水流模拟它们70°C的自然栖息地，细胞在30分钟内游动了长达1毫米的距离，方向变化很少。这种长距离的表面迁移由IV型菌毛驱动，促进细胞极的垂直附着以及细胞体的剪切诱导倾斜，导致前端朝向水流方向排列。对IV型菌毛丝及其动态的直接可视化显示，趋流性是由细胞极处附着减弱触发的，由ATP酶活性调节，这通过数学建模进一步得到验证。对栖热菌门（同义词嗜热栖热球菌）中的15种细菌菌株和物种进行的流动实验表明，正向趋流性在杆状栖热菌科中高度保守，但在球状嗜热栖热球菌中不存在。我们的研究结果表明，嗜热细菌通过对快速水流的物理刺激做出反应来到达其生态位，这是温泉环境中普遍存在的特征。这项研究突出了意想不到的生存策略，展示了对与表面相关生活方式的进化适应，否则游动细菌会被冲走。
