Bacteria are found in nearly every environment on Earth, from soil to oceans to hot springs. To survive, they need to move and find the best spots for growth. While we know a lot about how bacteria follow chemical signals or light, much less is understood about how they respond to physical forces like flowing water. This is especially important in hot springs, where water constantly rushes through the environment. If bacteria cannot resist being swept away, they may fail to find suitable niches for survival. By studying Thermus thermophilus, a heat-loving bacterium that lives in hot springs, we aimed to uncover how microbes manage to stay and even travel upstream in such fast-flowing conditions. Understanding these strategies gives us insight into how life adapts to extreme environments and how microbes colonize surfaces under challenging natural conditions.
We discovered that Thermus thermophilus, which lacks the usual propeller-like flagella, can still move long distances against flowing water. Instead, it uses tiny hair-like filaments called type IV pili that extend and retract like grappling hooks. Surprisingly, the bacteria could travel up to 1 millimeter in 30 minutes, which is a very long distance at their microscopic scale. Even more unexpected, this behavior—called positive rheotaxis—was found in several related hot spring bacteria with rod-shaped cells, but not in spherical bacteria of the same family. This shows that cell shape plays an important role in how microbes sense and respond to water flow. Our study reveals a previously unknown survival strategy: by moving upstream along surfaces, these bacteria avoid being washed away and can reach nutrient-rich spots in extreme environments like hot springs.
The research findings show how bacteria adapt to strong water currents by using pili instead of flagella. This insight helps microbiologists better understand microbial survival strategies in extreme environments, such as hot springs. Beyond ecology, it also inspires ideas in bioengineering—for example, how to design tiny robots that move in flowing liquids, or how to control bacterial movement in medical and industrial systems. Revealing these natural strategies not only deepens our knowledge of evolution but may also lead to innovative applications in biotechnology and environmental sciences.
Read the full journal article titled ‘Rapid water flow triggers long-distance positive rheotaxis for thermophilic bacteria’ in The ISME Journal. This article has been selected as Editor’s Choice for the month of July 2025.
Authors
- Naoki A. Uemura, The University of Electro-Communications, Japan
- Naoya Chiba, Tokyo University of Pharmacy and Life Sciences, Japan
- Ryota Morikawa, Tokyo University of Pharmacy and Life Sciences, Japan
- Masatada Tamakoshi, Tokyo University of Pharmacy and Life Sciences, Japan
- Daisuke Nakane, The University of Electro-Communications, Japan