We are SHPH-Shanghai, a dynamic iGEM team from Shanghai Pinghe School. We join together because we believe that our world is not perfect yet. Is there anything around us that does potential harm to our body? If yes, how can we solve the problem with biological methods? We thought about water pipe. It is hard to clean the water supply system because of nook of the machines and the turning angles of pipes. When tenacious biofilm forms on the water pipe, it can lead to detrimental consequences. The firm extracellular matrix of biofilm prevents the microorganisms inside the biofilm from being washed away or being in contact with disinfectors. Drinking water with biofilm will introduce pathogenic bacteria and fungi into the human body and cause serious infection and inflammation. Regarding the defects of the traditional chemical methods of degrading biofilm, our team hopes to introduce a harmless, sustainable, and effective biological method to degrade biofilm.
Biofilm is the slimy extracellular matrix formed when groups of cells adhere to each other and to a proper surface. It is a conglomeration of extracellular polymeric substances including polysaccharides, proteins and DNA. Our team finds that lactic acid produced by Lactobacillus delbruckii as a side-product is an acid with considerable effect of biofilm degradation. Lac. delbruckii is a bacterium that is found in the vagina of female; it is also a probiotic, so is commonly used in the food industry. Its harmless property makes it an excellent chassis bacterium for biofilm degradation in water pipes. In order to produce carbon recourses, lysozyme N-Acetyl-β-D Glucosaminidase is utilized to break 1,4-glucosidic bonds of polysaccharides. Sequence that codes for NAG is combined with sequence of Lactobacillus brevis that codes for S-layer protein signal peptide. S-layer protein signal peptide promotes adhesion and secretion of NAG. By using a linker as a connector, the unwanted steric effects on the functionality of NAG enzyme can be minimized. The combined sequence is then transferred into the acid producing Lac. delbruckii for expression. When the modified bacterium is introduced near the biofilm, it adheres to it and NAG is secreted. Hydrolyzed polysaccharides provide nutrients for Lac. delbruckii, which secretes lactic acid that further biofilm degradation. As pH of the system gradually drops below 3.5, hydrogen peroxide is secreted as a disinfector. It kills bacteria and is supposed to have a positive effect on the degradation of biofilm. Overall, our system creates a positive feedback loop for biofilm degradation and its effect is expected to be significant.