Washington, September 26: Engineers have observed and tracked the movement of E. coli in a liquid medium, which is similar to that of a kayak paddle.
Their findings will help lead to a better understanding of how bacteria move from place to place and potentially, how to keep them from spreading.
Scientists have long theorised that the cigar-shaped cell bodies of E. coli and other micro-organisms would follow periodic orbits that resemble the motion of a kayak paddle as they drift downstream in a current.
Until now, no one had managed to directly observe or track those movements.
Hur Koser, associate professor at Yale’s School of Engineering and Applied Science, previously discovered that interactions between the bacteria and the liquid current align the bacteria in a way that allows them to swim upstream.
“They find the most efficient route to migrate upstream, and we ultimately want to understand the mechanism that allows them to do that,” Koser said.
Koser, along with postdoctoral associate and lead author of the paper, Tolga Kaya, devised a method to see this motion in progress.
They used advanced computer and imaging technology, along with sophisticated new algorithms, that allowed them to take millions of high-resolution images of tens of thousands of individual, non-flagellated E. coli drifting in a water and glycerine solution, which amplified the bacteria’s paddle-like movements.
The team characterised the bacteria’s motion as a function of both their length and distance from the surface. The team found that the longer and closer to the surface they were, the slower the E. coli “paddled.”
It took the engineers months to perfect the intricate camera and computer system that allowed them to take 60 to 100 sequential images per second, then automatically and efficiently analyze the huge amount of resulting data, said an Yale release.
E. coli and other bacteria can colonize wherever there is water and sufficient nutrients, including the human digestive tract. They encounter currents in many settings, from riverbeds to home plumbing to irrigation systems for large-scale agriculture.
These findings will appear online in the September 29 issue of Physical Review Letters.
–Agencies