The system uses modified E. coli bacteria which produce different coloured pigments in response to varying levels of a particular micronutrient – zinc, in the current test. A pellet containing the modified bacteria is exposed to blood plasma from a group of test subjects, and after 24 hours the bacteria produce one of three pigments indicating low, borderline or normal levels of zinc.
No lab required
By using the bacteria, academics at the Georgia Institute of Technology hope to be able to reduce the need for the sophisticated and expensive equipment currently needed to test blood zinc levels. And while the current iteration is a proof-of-concept, the GIT team are refining the system to make it more portable and durable, and eventually to test for a greater range of micronutrients.
“We think this is just enough technology to meet the needs. The information we can provide could one day help nutritional epidemiologists and non-governmental organisations determine the populations of people that may need interventions to address nutritional deficiencies,” said Mark Styczynski, assistant professor in the School of Chemical and Biomolecular Engineering at GIT, who with his colleagues has recently produced a paper on the test in the journal Metabolic Engineering.
He said the research, which is funded in part by the Bill and Melinda Gates Foundation, is not aimed at testing individuals, but whole communities, to determine if an intervention is required. After collecting blood from a number of people, the samples would be spun in a simple centrifuge to separate the plasma for testing.
“Places where you are likely to encounter micronutrient deficiencies will typically be resource-poor countries, or perhaps locations suffering natural disasters,” said Styczynski. “These deficiencies aren't treated on an individual level, but are considered on a population level and used to treat a village or a region that may be affected. We could take samples from 50 or 100 people and be able to assess the nutritional status of an area.”
More tests to come
Next steps for the project include developing a system to freeze-dry the bacteria while maintaining viability in order to increase the test’s shelf life, reducing the time required to get a result, and improving the reliability of the pigment production. Beyond that, the GIT team plan to modify the system to detect other micronutrients, including vitamins – a process which may see them moving away from E. coli and using organisms such as yeasts.
“This is a convincing proof-of-principle, and we hope to begin the translational aspects of this system based on what we have already shown. It's a matter now of reducing this to practice for something that will ultimately be useful,” said Styczynski.
“Ultimately, we hope to be able to test for a whole suite of nutrients in a reasonably short period of time and at a relatively low cost because no equipment would be needed in the field,” he added.
Source: Metabolic Engineering
Published September 2015, doi:10.1016/j.ymben.2015.06.007
“Precise metabolic engineering of carotenoid biosynthesis in Escherichia coli towards a low-cost biosensor”
Authors: D. M. Watstein, M. P. McNerney, M. P. Styczynski