Overview

Our Iron Coli Project deals with hemochromatosis. Hemochromatosis is an autosomal recessive disorder which is the most frequent genetic disease in Europe as it affects over two millions people. It is caused by a mutation on the HFE gene, which leads to an overabsorption of iron in the upper region of the intestin - duodenum and jejunum - to the blood. On average, a hemochromatosic patient accumulates four times more iron than a healthy patient. This iron overload is stored in many organs and tissues, which eventually causes chronic insuficiences as heart, liver and kidney failures. The only available treatment for patients suffering from hemochromatosic nowadays is to remove up to 500 ml of blood at a frequency which varies from once a week to twice a year. Blood-lettings are time-consumming and are often barely tolerated by patients. That is why we wanted, with our projec,to find an alternative and complementary treatment for hemochromatosic by directly chelating iron in the intestin, preventing its absorption by the organism. We thus work on a engineered E. coli strain - Iron Coli - that could produce iron chelators in high iron concentration in the intestin.

To do so, we focused on a natural iron chelating molecule called enterobactins that is produced in iron starvation case by E. coli. For our project, we wanted to invert this natural behaviour so E. coli would produce these interobactins in high iron concentration. To deliver our bacteria right in the duodenum where it would prevent the iron absorption, we also worked on the design of a gastro resistant capsule.

As an initial step, we first wanted to know if our bacterial treatment would be accepted by the patients. To answer this question, we conducted a survey to directly ask for their opinion. It came out from the survey that a majority of hemochromatosic patients would actually agree on taking our treatment if it was allowed by the national agency for drug safety.Now that we knew our bacterial treatment would be accepted by the patient, we then think about all its potential consequences. We thus created a fault tree, considering two mains possible behaviour of E. coli in the intestin. It could either stay permantly -colonize - in the intestin or only temporarily. It came out that if E. coli stays permantly it involves too much risks and danger. So we focused on a flush strategy, meaning that E. coli stays temporarily in the intestin. We asked our modelling team is our bacterial treatment, based on this flush strategy, would be efficient. Their model predicted that our engineered E. coli could divide by two the amount of iron absorbed by a hemochromatosic patient. Knowing that our treatment would be accepted and beneficial to patients, we then focused on the biology of our project. We obtained two biobricks : an iron sensing device and a inverter signal system.

As a final step, we still have to clone the enterobactin operon after our inverter system. In the mean time, we wonder how much time it would take for our E. coli to produce enterobactin and if overproducing them would unbalance E. coli metabolism. A flux Balance Analysis and a differencial equation model showed us that the over interobactin production would take five hours and would required the addition of a substrate called chorismate.

Five hours is too long considering our flush strategy, that is why we worked on the improvement of the capsule design. We thus added HPMC into our capsule, which creates a visquous matrix in contact of water. This would slow down the intestinal flow and give enough time to our Iron Coli to sense iron and to produce enterobactin.

We are currently few steps aways to a final concrete treatment as the only work left we have is to clone the enterobactin biosynthesis. Through our project, we managed to made an integrated human practice study as well as creating useful models that both equally contributed to the realisation of our final project.