Engineered Bacteria Measure Caffeine Concentrations | Chemical & Engineering News
 
 
8
Facebook
Latest News
Web Date: March 21, 2013

Engineered Bacteria Measure Caffeine Concentrations

Synthetic Biology: Researchers transfer caffeine degradation pathway between bacterial species to produce easy-to-use biosensors
Department: Science & Technology | Collection: Life Sciences
News Channels: Biological SCENE, Analytical SCENE
Keywords: caffeine, synthetic biology, genetic engineering, biosensor, Escherichia coli, soda
[+]Enlarge
Caffeine Fiends
Bacteria engineered to degrade caffeine only grow in media supplemented with caffeinated soda (bottom image). In both photographs, the tube on the left is growth media without soda, and the tube on the right contains media and soda, either caffeinated or decaffeinated (top image). The tube containing caffeinated soda turns cloudy as the bacteria grow.
Credit: ACS Synth. Biol.
20130321lnj1-soda
 
Caffeine Fiends
Bacteria engineered to degrade caffeine only grow in media supplemented with caffeinated soda (bottom image). In both photographs, the tube on the left is growth media without soda, and the tube on the right contains media and soda, either caffeinated or decaffeinated (top image). The tube containing caffeinated soda turns cloudy as the bacteria grow.
Credit: ACS Synth. Biol.

With the growing energy drink craze, people want to know how much caffeine is in their beverages. One team of researchers has developed a unique way to measure caffeine levels. They’ve engineered Escherichia coli so that the bacteria’s growth depends on the concentration of the invigorating compound (ACS Synth. Biol., DOI: 10.1021/sb4000146).

High levels of caffeine can be toxic to some bacteria, but one species called Pseudomonas putida CBB5 has a multienzyme biochemical pathway that degrades the chemical into xanthine and formaldehyde.

For a synthetic biology competition, a student team from the University of Texas, Austin, led by Jeffrey E. Barrick, wanted to transfer that caffeine degradation ability to E. coli. Making such a transfer is not simple, but E. coli is one of the more easy bacterial species to engineer.

The team assembled an engineered genetic package, in part, from P. putida genes for the pathway. They then inserted the package into an E. coli strain unable to make guanine, a DNA base that is necessary for bacterial growth. If the genetic instructions worked, the genes would code for proteins that removed two methyl groups on caffeine to make xanthine, an intermediate in guanine biosynthesis. As a result, these engineered bacteria would only grow in the presence of caffeine.

When the scientists added the bacteria to cultures supplemented with caffeinated sodas, espresso, or energy drinks, the microbes thrived. But nothing grew in cultures lacking the caffeinated beverages. The amount of bacterial growth also was proportional to the amount of caffeine in the culture. Using microbe growth, the researchers measured caffeine levels that mirrored reported values for those beverages.

As caffeine biosensors, Barrick says these bacteria are accurate and simple enough for high school students to use.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society
Comments
Jiang Du  (March 22, 2013 4:42 AM)
Using hplc should be more easy to measure caffeine level. maybe it's the difference between chemist and biologist.
William Penrose  (March 22, 2013 12:52 PM)
A clever accomplishment, especially as an educational aid. As a practical method for caffeine, of course, it's lacking in many ways, since the growth rate of bacteria depends on much more than the concentration of one nutrient. But I can already think of a dozen ways to use it as a teaching tool, including demonstrating the limitations of a given method.
Mike Hammerling  (March 22, 2013 6:30 PM)
It's not growth rate that is used to measure the caffeine content, but rather the final cell count. For the guaB knockout strain used in the paper, caffeine (as a precursor for guanine) is the limiting nutrient in minimal media.

That's really not the cool part of the paper, though. Indeed, HPLC is better for this purpose. The cool part is the full characterization of the operon, including genes whose functions were previously unknown, and the refactoring and porting of the operon into a different organism.
Amit Paul  (March 26, 2013 7:57 AM)
It is really a mind blowing achievement.What is the name of the enzymes and corresponding genes which remove methyl group from caffeine and make xanthin.
Leave A Comment