Project overview

The Bactissile is the future of microbial combat. In your body, in drinking-water, in important ecosystems, in food and in sewage plants harmful bacteria can fester and cause problems both for the individual and for society as a whole. The conventional way of combating these bacteria involves chemicals such as antibiotics that kills not only harmful microbes, but the beneficial ones as well. Disturbing the natural bacterial flora in the body and in nature may in fact cause as much trouble as the harmful bacteria that we intend to kill in the first place.
Enter the Bactissile The Bactissile tracks and kills one type of bacteria and leaves other species intact.
By sensing that specific harmful bacteria, targeting it and killing it, the Bactissile is a modern weapon to fight bacteria in many different environments, without affecting the surroundings. Sensing, targeting and killing are the backbone of the Bactissile, but to prove it functional we needed to choose one of the many possible pathogens to target. In light of the numbers of deaths due to gut bacteria in the world, and the menacing issue of antibiotic resistance we decided to prove our concept by battling the gut pathogen Yersina enterocolitica.
The natural approach to battling a harmful gut bacteria is through a beneficial gut bacteria. This is why we intended to introduce the Bactissile system in a probiotic, such as Lactobacillus, which last years Team from Uppsala worked with.

Yersinia enterocolitica

Y. enterocolitica is a pathogenic bacteria related to Y. pestis, the cause of the Bubonic plague. Y. enterocolica thrives in uncooked food and grows well even in refrigerated temperatures. This pathogen is especially dangerous for young children, causing fever, diarrhea and severe dehydration. All pathogens causing food poisoning and diarrhea are particularly dangerous in underdeveloped countries, where hygiene, access to water and medical care is highly inaccessible.

Our system

We have constructed a two-mode system. When our Bactissile is far away from our target, Y. enterocolitica, the first mode will be active, the Tracking mode. This entails that our Bactissile’s production of CheZ and a silencing RNA spot42_USP45 is induced by having the activator YenR interact with the recognition region, the yenbox, and thereby inducing the strength of the wildtype promoter fused to it. The increased amount of CheZ will result in that our host will take big leaps, randomly looking for Y. enterocolitica. Meanwhile the silencing RNA will silence the translation of our killing substance, the bacteriocin CFY, by binding to its corresponding RNA.
Insert Tracking mode on pic https://static.igem.org/mediawiki/2014/c/cb/TrackingMode_new2_Uppsala2014.png
Once Y. enterocolitica gets close to our Bactissile, Y.enterocolitica’s own signaling molecule will start to enter our system and interact with our activator, YenR. When the signaling molecule binds to YenR, YenR will lose its active shape and thereby its ability to interact with the yenbox, and can no longer induce the expression of the promoter. When this happens, the amount of CheZ and of the silecing RNA spot42_USP45 will decrease, resulting in that our host will stop moving and basically start tumbling in circles. Also, the amount of the silencing RNA spot42_USP45 will not be balanced with the RNA:s coding for the killing substance CFY, which will lead to initiation of the production of CFY. These two processes is what we define as the trigger of the Killing mode.
https://static.igem.org/mediawiki/2014/f/f6/KillingMode_Uppsala2014.png
Colicin molecules will start being exported out of our host, interfering with the structure of Y. enterocoliticas membrane. When the concentration of Colicin secreted reaches the threshold of 1.4e10 molecules/mL the dosage will become lethal to Y. enterocolitica.