Team:Fudan/Description
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Description
Inspiration
Lactose intolerance is a common disease in China, prevalence of Primary Lactase intolerance has reached up to 95%-100% , but some adults with lactose intolerance don't care about it because they can just live a life without milk. When it comes to babies, things are different.
This year, in January, when Yichen Gong (One of our team members) was doing voluntary work at Obstetrics and Gynecology Hospital of Fudan University, she found that lots of babies were suffering from lactose intolerance. Milk is very important to them, so they can't avoid drinking milk to treat this disease. At hospital, she realized that there are two main ways in treating lactose intolerance, one is to use lactase and another is to use probiotics, but both ways are inconvenient for babies.
Click to see more about existing treatments…
During the process of investigation, we concluded that although there exist many commercialized products claiming that they can ease symptoms of lactose intolerance, they haven’t been widely chosen by many families. We dig further and found out that these products, either it be probiotic or lactase preparations, don’t have strong survivability in vivo, and thus their efficiency is reduced to a large extent.
Based on these findings, we came out with a synbio proposal to solve lactose intolerance by strengthening the survivability and the efficiency to digest lactose in probiotics. After through consideration and discussion, we decided to use Nissle 1917, an E. coli sub-strand which has been widely proved by literature as a probiotic for treating intestinal diseases, as our chassis.
Description
As we intended to remold E. coli Nissle1917, a kind of commonly used probiotic, to provide a universal platform for intestinal metabolic disease treatment, the next question is how to improve its survivability and lactose digestion ability. We intended to achieve this by introducing 3 systems: microcin system that gives our chassis high competitiveness against intestinal symbiotic as well as harmful bacteria, acid resistance enhancement remold that enables our chassis to perform strong stress resistance against gastric environment, and the quorum sensing system to avoid uncontrolled reproduction and assure its safety.
AR systems
Since our project aims at patients of all age groups, it’s better for us to provide our product in the form of powder as this is more suitable for imfants and the old. Therefore, we would have to deal with the problem of bacteria survivability in gastric environment, so we came up with the idea of remolding AR systems in Nissle 1917.
the remold of acid resistance system is completed by knocking out global-regulatory transcriptional factor H-NS, which takes part in down-regulating the expression of GadC, YbaS and many other transportases and glutaminases required for acid resistance (AR) systems in prokaryotes1. By knocking out H-NS, the acid resistance system in our chassis is strengthened, thus protecting remolded Nissle against gastric environment.
Microcin
If we want our engineered Nissle to stay in gut for longer time, we must enhance its ability to create a niche for itself. In other words, it must have to “win the competition” against other intestinal symbiotic as well as harmful bacteria. that’s why we decided to transfer the gene cluster that expresses microcin Mccb17, a type of antimicrobial peptide that had just been thoroughly characterized2, into Nissle 1917.
With the help of Mccb17, Nissle 1917 will face less survival and competition pressure, thus enabling our product to become a long-acting solution to lactose intolerance.
Quorum sensing
We don’t want our product to grow uncontrolled in vivo, and we don’t want it to grow too slow due to heavy burden either. These thoughts prompted us to figure out a controlling circuit that regulates the expression level of microcin and lactase. Finally, we decided to apply quorum sensing system into our project in that it has the potential to control its own flora scale when coupled with microcin Mccb17, which we further demonstrated in Design.
With the help of quorum sensing system, our product is able to “switch on” protection units that gives Nissle self-immunity against Mccb17 when the flora scale is small, enabling Nissle to create a niche for itself and grow faster. Accordingly, when flora scale reaches a certain level, protection units will be shut off, resulting in death and the reduction of living bacteria number, thus preventing potential risk of intestinal flora disturbance.
Reference
[1] Gao, X., Yang, X., Li, J., Zhang, Y., Chen, P., & Lin, Z. (2018). Engineered global regulator H-NS improves the acid tolerance of E. coli. Microbial Cell Factories, 17(1), 118. doi:10.1186/s12934-018-0966-z
[2] Collin F, Maxwell A. The Microbial Toxin Microcin B17: Prospects for the Development of New Antibacterial Agents. J Mol Biol. 2019;431(18):3400–3426. doi:10.1016/j.jmb.2019.05.050S. Duquesne, D. Destoumieux-Garzón, J. Peduzzi, S. Rebuffat. Microcins, gene-encoded antibacterial peptides from enterobacteria Nat. Prod. Rep., 24 (2007), p. 708, 10.1039/b516237h