The goal of our project is to develop a hybrid flora designed to effectively eliminate pathogenic bacteria from the environment, thereby reducing the risk of infection. To achieve this goal, we plan to use a screened strain of the chassis bacteria that will be broadly applicable and harmless. We will utilize our experience in hybrid flora modification to reduce the potential impact of plasmid vectors on the strain by integrating new genes into the DNA of the chassis bacteria.
In terms of biosafety, we have designed two suicide switching circuits to ensure that our strains can self-destruct quickly and efficiently under any unexpected circumstances. One of the suicide mechanisms involves the ccdB protein, a toxic protein, which we plan to introduce into E. coli 1917 (DE3) by means of plasmid import. We have successfully introduced a plasmid containing the ccdB sequence and confirmed its successful introduction by gene sequencing.
We further explored the interaction between LapB and LpxC . An increase in LapB promotes the degradation of LpxC, which is responsible for the negative feedback regulation of lipopolysaccharide synthesis. yehM gene prevents the degradation of LpxC and helps in the delivery of endosomal material to the outer membrane. By mutating the LapB gene, we were able to increase its content, thereby decreasing the amount of LpxC, and the strain will die when the LpxC content drops to very low levels. We have introduced the EGFP-lapB plasmid and its multiple synonymous codon mutants into Nissle 1917 (DE3) and are comparing their lethal efficiency.
Although the time constraints of the competition prevented us from completing all of the anticipated screening tasks, we will continue our research to screen for the most suitable suicide switches. These findings will be applied to our final "protector" strain to ensure its safety and efficacy in real-world applications.
