(Click on the image to play the movie)

 

Worm Tracking

Left: 1mm long C. elegans at 2.5x real speed crawling on agar. Right: An approximate view of where the worm is crawling on the plate is shown by the red rectangle. A copper ring (6cm diameter) is used as a worm corral.

 

 

C. elegans Thermotaxis

N2 worms on an linear thermal gradient from left (hot) to right (cold). The set-point temperature of the worms is located approximately near the center of the plate. Note that the worms crawl in straight lines along isotherms. 30x real speed, 9cm diameter NGM agar plate.

 

 

Thermal Migration. N2 worms on an linear thermal gradient from left (hot) to right (cold). The set-point temperature of the worms is located to the right of the plate. Note that the worms move randomly but migrate to the right. 30x real speed, 9cm diameter NGM agar plate.

 

 

As worms crawl on an agar plate, it moves its head back and forth in a sinusoidal motion. We can steer worms in the clockwise or counter-clockwise direction by applying small pulses of heat with an IR laser at different phases of the head swing. This suggests that the worm can make spatial measurements by comparing temperatures on the left and right side of its body as it navigates temperature gradients. Here is a movie demonstrating this control.

 

 

Processing of worm images

We use image processing packages in LabVIEW and MATLAB to make quantitative measurements on the worm images taken by the worm tracker. First we isolate the worm (red worm) from the raw image by using object filters. We then can make measurements such as the measuring orientation of the worm or do additional processing such as skeletonizing the worm.

 

 

Thethered and swimming E. coli

E. coli motor behavior can be studied by tethering single bacteria to a
microscope coverslip via a single flagellar motor. Here we have a field
of multiple cells tethered by single motor, viewed under phase microscopy.

 

 

 

A phase-microscopy video of swimming E. coli