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Project Background

What are integrons?

Integrons are systems which can capture and utilise mobile genetic elements known as gene cassettes, and which are found in a vast array of bacteria. Cassettes are often associated with antibiotic resistance and are a significant factor in the spread of antibiotic resistance between bacteria. Gene cassettes with an attC recognition site are site selectively recombined into an attI recognition site by the integron integrase. Insertion of cassettes can continue to occur at the AttI site, and with much lower frequency at the AttC sites, resulting in a long array of cassettes which can be expressed from a constitutive promoter (Pc) just upstream from the AttI. Cassettes may also be from the array,

There are a few classes of integrons, but the first to be discovered and most well-known are the Class 1 integrons. Class 1 integrons are the most medically important class because of their involvement with antibiotic resistance in pathogenic bacteria. As shown in the diagram on the right, Class 1 integrons are defined by the presence of a conserved sulfonamide resistance gene on the outside of the array. The cassettes found within class 1 integrons are usually antibiotic resistance genes.

Since the integration of new cassettes is simultaneous with expression by the constitutive promoter, the system can conceivably be used for pathway optimisation by gene shuffling. This means that new insertions are immediately tested and selected for if beneficial.

An extensive review about integrons can be found here.

What are we doing?

We are seeking to design biobrick compatible, completely controllable class 1 integron components that can be used as a novel, convenient and selective cloning system in lab strains of E. coli, which normally do not contain integron systems. Additionally, we are investigating regulation of natural transformation mechanisms in E. coli in an attempt to allow uptake and recombination of attC containing genetic elements with added convenience.

Why is this cool?

By re-building nature’s modular genetic shuffling machine, we aim to provide a novel tool for Synthetic Biologists AND ALSO create an experimental system in which we can more precisely understand integrons.

Integrons in iGEM

Integrons have been encountered before in iGEM for different purposes:

Further Reading

Nature Review Article talking about Integrons and bacterial evolution.

Earlier Review by University of Sydney Professor Ruth Hall.

The SOS Response and Integrons

With thanks to: