Team:Tsinghua/Description
Description
Biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. It is a complex structure composed by germs and its secretion[1]. It can attach to the surface of the equipment or inner-surface of the pipelines. Longer it presents, harder it can be removed. The biofilm provide a cozy micro-environment for the bacteria and prevent them from the mechanical and chemical interference, which make them really difficult to be removed[2]. In most conditions, biofilm do harm to human beings. It will contaminate the product or even food with bacteria fall from the biofilm. Food-borne diseases caused by pathogenic microorganisms are the main hidden danger of food safety. About 80% of persistent bacterial infections in the United States are related to bacterial biofilms[3]. Biofilm will also affect a series of life scenarios such as industrial production, sewer pipes, swimming pools, etc. Biofilms tend to form in hard-to-reach places that cannot be cleaned regularly. These places provide favorable conditions for bacterial growth and are particularly difficult to disinfect.
Pseudomonas aeruginosa is one of the most common biofilm-bacteria lived in the pipeline system[4]. The biofilm it generated may block the pipeline and cause a huge amount of financial lost. What’s more, P. aeruginosa itself is pathogenic which can cause a lot of human disease. P. aeruginosa in the water supply pipeline, swimming pool or medical equipment will do harm to people health[5]. While they are hard to be eliminated because of the biofilm. And most pipelines are too tiny for mechanical elimination and chemical agent is hard to penetrate the biofilm. Other approaches like energy uncoupling, enzymatic hydrolysis or phages are either need harsh conditions or too limited to a specific application environment[6][7][8]. The biofilm problem is common in our daily life while its cleaning is still a world-wide problem hard to be solved.
Our project, NO mediated biofilm allayer(NBA), is purposed to utilize engineered E.coli to produce signal molecule nitric oxide to remove the biofilm of P.aeruginosa[9]. When the engineered bacteria senses the QS molecule BHL from P.aeruginosa bioflim[10], it is expected to be activated and express exogenous gene NOS(Nitric Oxide Synthase), producing NO as a signal molecules and finally leading to the dispersion of biofilm. We also designed the suicide module to keep the bio-safety for the engineered bacteria. This novel approach have the advantages that the engineered bacteria can easily get into any kinds of tubes and enter the biofilm. And NO is a gaseous molecules which can easily penetrate the extracellular matrix. It is very promising and bring a new sight to biofilm cleaning.
In a word, the engineered germs can recognize the biofilm and release NO to eliminate it. With the great advantages of synthetic biology techniques, the project NBA aims to provide a feasible solution to P.aeruginosa biofilm contamination in industry and household devices.
In the homepage, you just experienced an epic RPG game of a knight conquering a castle. Although the story itself is fabricated, the process is a real story constructed by our project “NO induced Biofilm Allayer”. It is an anthropomorphic expression of how do we eliminate the biofilm in the pipelines with our engineering bacteria. Here are some explanations.
The Knight of E.Coli——The engineered bacteria
We transformed genetic modified plasmids into Escherichia coli DH5 α to create the engineered bacteria. By adding them to the pipeline, they are able to eliminate the biofilm.
Goblin——Pseudomonas aeruginosa
One of the most common gram-negative bacteria which generate biofilm. It is a kind of opportunistic pathogen with strong resistance. It is harm to people and hard to be removed.
Sword of NOS——Nitric Oxide Synthase
Nitric oxide synthases (EC 1.14.13.39) (NOSs) are a family of enzymes catalyzing the production of nitric oxide from L-arginine as the function below:[11]
2 L-arginine + 3 NADPH + 3 H+ + 4 O2 ——2 citrulline +2 nitric oxide + 4 H2O + 3 NADP+
The light of the sword——Nitric Oxide
NO is an important cellular signaling molecule which can activate the collapse of biofilm. It is a gaseous molecules which can penetrate the biofilm easier.
Castle——Biofilm
A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances.
Castle Bricks——Protein and Polysaccharide
Secreted by Pseudomonas aeruginosa as extracellular matrix in order to construct the biofilm. They provide mechanical and chemical resistance. There are also lipids and DNA.
Esoterica of BHL——BHL molecules
One of the quorum sensing signal molecules generated by the bacteria which forms biofilm. C4-HSL is such a signal generated by Pseudomonas aeruginosa, which can be a specific symbol of the biofilm.
Ancient Key to Esoterica——RhIP BHL sensor
A molecular switch located at the upstream of NOS. When engineered bacteria senses BHL, the switch will be switched on and the downstream biochemical reaction will start. It is making sure that our engineered bacteria will only express NOS in the biofilm.
Holy Light——Suicide Module
We built a suicide module to keep the bio-safety of the engineered bacteria. When exposed in the blue light, the molecular switch will be activated. The downstream LexRO system will make the bacteria death. So that the engineered bacteria can only live in the pipeline.
Watch our promotion video to get better understanding !
Due to the COVID-19 pandemic, we are not allowed to return school until September. Time period of our wetlab progress and offline Human Practice is dramatically delayed from eight to only TWO MONTH! We worked hard in very limited time and still get a lot of results, HP experience, collaboration, wiki and posters. We designed and successfully demonstrate an interesting circuit against the biofilm. Now we are proud to introduce our project “NO induced Biofilm Allayer | NBA” to you！
Reference:
[1]López D, Vlamakis H, Kolter R (July 2010). "Biofilms". Cold Spring Harbor Perspectives in Biology. 2 (7): a000398. doi:10.1101/cshperspect.a000398.
[2] Hall-Stoodley L, Costerton JW, Stoodley P (February 2004). "Bacterial biofilms: from the natural environment to infectious diseases". Nature Reviews. Microbiology. 2 (2): 95-108. doi:10.1038/nrmicro821.
[3] Gupta P, Sarkar S, Das B, et al. Biofilm, pathogenesis and prevention − a journey to break the wall: a review. Arch Microbiol, 2016, 198: 1 −15.
[4] Høiby N, Ciofu O, Bjarnsholt T (November 2010). "Pseudomonas aeruginosa biofilms in cystic fibrosis". Future Microbiology. 5 (11): 1663–74. doi:10.2217/fmb.10.125.
[5] Balcht A, Smith R (1994). Pseudomonas aeruginosa: Infections and Treatment. Informa Health Care. pp. 83–84. ISBN 978-0-8247-9210-7.
[6] Leroy C, Delbarre-Ladrat C, Ghillebaert F, et al. Effects of commercial enzymes on the adhesion of a marine biofilm-forming bacterium. Biofouling,2008,24(1):11-22.
[7] Jiang B, Liu Y. Energy uncoupling inhibits aerobic granulation[J]. Applied Microbiology and Biotechnology,2010,85(3):5895-95.
[8] Goldman G, Starosvetsky J , Armon R. Inhibition of biofilm formation on UF membrane by use of specific bacteriophages. Journal of Membrane Science,2009,342(1-2):145-152.
[9] Barraud N, Storey M V, Moore Z P, et al. Nitric oxide-mediated dispersal in single- and multi-species biofilms of clinically and industrially relevant microorganisms .Microb Biotechnol,2009,2
(3):370-378.
[10] Lam H, Oh D C, Cava F, et al. D-amino acids govern stationary phase cell wall remodeling in bacteria [J].Science,2009,325(5947): 1552-1555.
[11] Knowles RG, Moncada S (March 1994). "Nitric oxide synthases in mammals". Biochem. J. 298 (2): 249–58. doi:10.1042/bj2980249
