Roland Piquepaille's Technology Trends
How new technologies are modifying our way of life

dimanche 15 février 2004

I know you talk to your kids to teach them new things. I'm even sure you also talk to your computer. So why not teaching bacteria to do new tricks by talking with them? This is what did a team from the University of California at Los Angeles (UCLA), according to this fascinating story published by Nature. More precisely, they taught cells a new 'language,' turning them into tiny robots able to produce hydrogen or poisons to kill ill cells.

Bacteria already communicate with each other by sending out chemical signals. A cell might release a certain chemical in response to stress, for example, letting other cells nearby know they should prepare for some unpleasant environmental conditions.
But cells typically have a limited number of stimuli that provoke these chemical warnings, and a limited number of chemicals that they can use to communicate. James C. Liao and co-workers at UCLA wondered if they could get bacteria to talk using a different chemical.
They started by stitching a 'module' of control genes into the genome of Escherichia coli (E. Coli) bacteria -- these genes can switch on or off other genes naturally present in the bacteria.

Here is a picture of an E. Coli DNA microarray (Credit: UCLA).

An E. Coli DNA microarray
The team managed to control the conversation by adjusting the acidity of the cell medium. In non-acidic conditions, it takes more acetate to trigger a cell, so there needs to be a lot of cells secreting acetate to start the conversation. In acidic conditions, just a few cells are enough to start a chat.

What can we expect from this research?

"You could use this approach as a Trojan horse idea to combat disease," says Jeff Hasty, who works on gene modules at the University of California, San Diego. Modified cells of pathogenic bacteria could be introduced into a natural colony of the same cells, he says. Then, at a given chemical signal, the modified cells could be told to produce compounds that would kill off the bacteria.
Liao and colleagues think they can use the same technique to talk to other species of bacteria too. Eventually, they hope to create dialogue in diverse communities of cells that would ordinarily just ignore each other.

This research work has been published under the name "Design of artificial cell-cell communication using gene and metabolic networks" by the Proceedings of the National Academy of Sciences. Here is the beginning of the abstract.

Artificial transcriptional networks have been used to achieve novel, nonnative behavior in bacteria. Typically, these artificial circuits are isolated from cellular metabolism and are designed to function without intercellular communication. To attain concerted biological behavior in a population, synchronization through intercellular communication is highly desirable. Here we demonstrate the design and construction of a gene-metabolic circuit that uses a common metabolite to achieve tunable artificial cell-cell communication.

Finally, for your viewing pleasure, here is a picture of an E. coli engineered by UCLA graduate students to produce astaxanthin (orange), compared to the native cells (off-white) (Credit: UCLA). This image comes from the Molecular and Cellular Bioengineering group at UCLA.

E. Coli producing astaxanthin (in orange)

Sources: Philip Ball, Nature, Febuary 12, 2004; and various websites

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