Abstract

Molecular biosensors are useful tools that detect metal ions or other potentially toxic chemicals.
However, the efficiency of conventional sensors is limited in mixed metals substrates, which is
the common way they are found in nature. The use of biosensors constructed from genetically
modified living microbial systems has the potential of providing sensitive detection systems for
specific toxic targets. Consequently, our investigation was aimed at assembling different genetic
building blocks to produce a focused microbial biosensor with the ability to detect specific metals.

This objective was achieved by using a synthetic biology approach. Our genetic building blocks,
including a synchronized ribosomal switch–iron ion channel, along with sequences of promoters,
metal-binding proteins (Fe, Pb), ribosomal binding sites, yellow fluorescence reporter protein
(YFRP), and terminators, were constructed within the same biobrick in Escherichia coli. We used an rpoS ribosomal switch containing an aptamer, which responds to the specific metal ligands, in synchronization with an iron ion channel, TonB. This switch significantly stimulates translation, as expressed by higher fluorescence, number of colonies, and concentration of RNA in E. coli.

The positive results show the effectiveness of using genetically tailored synchronized ribosomal
switch–ion channels to construct microbial biosensors to detect specific metals, as tested in iron solutions.