The new approach, described this month in Nature Methods, uses optical traps, microfluidic chambers and fluorescence to get an improved picture of how E. coli get around.
The microfluidic chambers provide a controlled environment in which the bacteria swim, and allow the researchers to introduce specific stimuli – such as chemical attractants – to see if the microbes change direction in response to that stimulus.
Optical traps use lasers to confine individual cells without impeding their rotation or the movement of their flagella. University of Illinois physics professor Yann Chemla, who co-led the study with physics professor Ido Golding, calls the optical traps “bacterial treadmills.” Movement of the bacterial cell alters the light from the laser, allowing the researchers to track its behavior.
Fluorescent markers enhance visualization of the bacteria and their flagella under a microscope.
Three to six helical flagella emerge from various points along E. coli’s rod-shaped body.
When they rotate in a counterclockwise fashion (as seen from behind), they gather into what looks like a coordinated bundle that pushes the bacterium forward, causing it to corkscrew through its environment. But when one or more flagella rotate in the opposite direction, they splay apart, reorienting the bacterium.
This “run and tumble” behavior has long been of interest to scientists for two reasons, Golding said. First, the elaborate mechanics of bacterial swimming “tell you a lot about biomechanics,” he said. And second, “it serves as a paradigm for the way living cells process information from their environment.”
Earlier studies have been unable to follow individual bacterial cells moving in three dimensions for more than about 30 seconds, the researchers said. And it is nearly impossible to determine what cues are spurring a cell to move in a given direction. The new method addresses both of these problems without altering the normal behavior of the bacterium, they found.
“Because the cell is immobilized, what we do is change the environment around it,” Chemla said. “We can set up a flow cell that has two different concentrations of some chemical, for example, and see how the bacterium responds. Technically we’re moving the swimming pool relative to the swimmer,” he said.
The new approach allows the researchers to track a single bacterium as it swims for up to an hour, “which is orders of magnitude above what people could do before,” Golding said. This will offer a new look at questions that so far have been unanswerable, he said.
“For example, some people have asked whether E. coli has a nose. Does it have a front and back?” Golding said. The team’s observations indicate that while the bacterium can travel in either direction, most E. coli have “a pronounced preference” for one over the other, he said.
The researchers found that after most tumbles, a bacterium usually continued swimming in the same general direction, but that about one in six tumbles caused it to change direction completely. They were also able to quantify other features of bacterial swimming, such as changes in velocity and the time spent running and tumbling. The new technique will allow researchers to address many more questions about this model organism, they said.
“That’s the typical way biology moves forward,” Golding said. “You develop a new measurement capability and then you can use that to go back and look at fundamental questions that people had been looking at but had no way of answering.”
The study is a project of the National Science Foundation’s Center for the Physics of Living Cells at the University of Illinois, which promotes collaboration across disciplines, the researchers said.
Diana Yates | University of Illinois
For a chimpanzee, one good turn deserves another
27.06.2017 | Max-Planck-Institut für Mathematik in den Naturwissenschaften (MPIMIS)
New method to rapidly map the 'social networks' of proteins
27.06.2017 | Salk Institute
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
27.06.2017 | Power and Electrical Engineering
27.06.2017 | Information Technology
27.06.2017 | Physics and Astronomy