Laser tractor beam used to trap bacteria

Posted Jan 1, 2017 by Tim Sandle
Viewing the activities of the microbial world is key for the study of disease and for drug development. German researchers have developed a new method for capturing and trapping bacteria using lasers.
This key experiment shows the successful protection of a phage-sensitive bacterial strain against a ...
This key experiment shows the successful protection of a phage-sensitive bacterial strain against a virus. Top-right - bacteria growing in the absence of a virus; Top-left - holes in the culture caused by an infecting virus; Bottom - when equipped with specific CRISPR defense system components, the bacteria became resistant to the virus.
John van der Oost
The conventional way of studying bacteria is to mount them onto a slide and view them under a microscope. This is fraught with difficulty, including a loss of cell viability and the effect of the slide substrate being artificial (so the organisms may not behave as intended, such as sticking to a surface when they should be free-flowing).
Using laser technology, Bielefeld and Frankfurt University scientists, led by Professor Robin Diekmann, have devised the means to trap biological cells and allow for their study at high resolution. They describe this as a little like a ‘tractor beam’ as might appear in a science fiction movie.
The new method is seen as a breakthrough, allowing scientists to view ultra-clear images of DNA in single bacteria (this is at a resolution of down to 0.0001 millimeters). One of the lead researchers, Dr. Thomas Huser, who is a physicist, told Controlled Environments magazine: “Our new method enables us to take cells that cannot be anchored on surfaces and then use an optical trap to study them at a very high resolution. The cells are held in place by a kind of optical tractor beam.”
The laser is based on infra-red light and it is invisible to the human eye. The captured bacteria are not held in place; instead the technology allows them to be turned and rotated, enabling better imaging. The organisms can be studied using super-resolution fluorescence microscopy, which allows considerable cellular detail to be seen as a three-dimensional image. The image is formed as a result for fluorescent radiation.
One of the main uses of the technique will be to view the interactions between bacteria and human cells, such as red blood cells. This will allow better realization of how bacteria penetrate cells.
The findings are published in the journal Nature Communications. The paper is “Nanoscopy of bacterial cells immobilized by holographic optical tweezers.”