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genetically engineered a group has constructed a mutant Escherichia coli in the biosensor system that triggers the movement of the flagellum.

If inoculated wild type, call-1 strain in semisolid agar the bacteria can "Swim" and spread around:

wild strain:

(*) click on image to view larger

In the mutant strain, called strain-2, has the deleted gene chez encoding the protein Chez. Without this protein the flagellum movement control is lost.

First question: How do you behave the mutant? Does semisolid agar diffusion will be higher or lower than in the wild strain?

A the research team then takes the strain lacking Chez and I introduced a plasmid containing the gene for this protein, but under the control of a ribointerruptor (riboswitch) . This new strain is called strain-3.

The ribointerruptor works as follows:

• In the absence of a molecule, let's call it molecule A, the gene messenger mRNA chez can not be translated by ribosomes.


• In the presence of the molecule A, the mRNA of the gene chez can be translated by ribosomes.

Researchers Strain-3 inoculated in a semisolid agar plate where it has added a drop containing the molecule A in one side of the plate.

Second question: How will behave Strain-3 at the plate? Do or get closer to the molecule A?


This research group also introduced the gene for Green Fluorescent Protein or GFP ( F G reen luorescent P rotein ) in the strain-3, thus the strain-4. This bacterium emits green fluorescence by the protein

Third question: What practical use could be strain-4?

(*) Figure produced from the book " Brock. Biology of microorganisms " Pearson Publishing