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Monday, October 28, 2013

Capturing and observing individual bacteria

If you could observe individual bacteria, you would see that they lead a rich life of interaction with each other and their environment. Bacteria cooperate and they compete with each other. These relationships are largely driven by chemical cues in the immediate vicinity, which could be no more than a few micrometers across. Therefore, if you’re going to parse out how these microenvironments affect bacteria, including their reproduction and virility, you’ll need to be to make really tiny little test chambers for them. That’s exactly what Jodi Connell and her colleagues from the University of Texas at Austin did.

The researchers mixed bacteria with warm gelatin and a photosensitive molecule that promotes chemical cross-linking when excited. As the gelatin cools, it slowly solidifies with the bacteria suspended throughout. A carefully aimed laser results in sturdy, cross-linked microstructures around individual bacteria. In other words, the scientists made tiny cages around the bacteria.

The structures are imaged in red through confocal fluorescence, while the bacterial microcommunities are imaged in green. 
Credit: Jason Shear

The technique can be used to mix small numbers of bacteria from the same or different species together under different conditions. The gelatin matrix used is also highly permeable to a variety of compounds, allowing the researchers to test how the bacteria react to all sorts of molecules. Of particular interest was how normally susceptible bacteria can be sheltered from antibiotic toxicity by the presence of resistant bacteria.

You can see one such experiment below:

Jodi L. Connell, Eric T. Ritschdorff, Marvin Whiteley, & Jason B. Shear (2013). 3D printing of microscopic bacterial communities Proceedings of the National Academy of Sciences of the United States of America DOI: 10.1073/pnas.1309729110.

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