2 The Story - Toxic AppleThe idea is from the bacteria's own selection system and we try to take advantage of it. We intend to construct a system through which bacteria will transfer the death gene by themselves. The question is bacteria won’t keep the gene that play negative role to their survival and will drop the system someday. In order to maintain or even widely spread the suicide system we endow it with the sweet gene that will has positive affection to the multiplication of bacteria. Regularly, the sweet gene expresses to make bacteria glad to accept it, promoting the spread of plasmid from one bacteria to another through conjugative transfer (a process bacteria inherently own) in some degree. Once its account reaches a certain threshold, the dead gene switch will turn on, resulting in the death of the host bacteria. So, function of the whole device can be abstractly described as the toxic apple in fairy tale.
3 Five Objective Parts Involved3.1 Environment Condition report Genes This part is aim at report the temperature of the environment.( K873002 is a heat shock promoter that transcribes when the temperature suddenly rises from37℃ to 42℃). Because the sweet genes show obvious benefits to the bacteria under the heat shocking condition, we would like to set a GFP reporter in order to ensure the sweet genes effects. 3.2 Regulator Genes This part has regulative function. At the present stage of our project, we wish to improve the conjugation rate by increasing the density of bacteria. So, we use K873001(refer to the flagellar motility of E.coli) and R0084(At low osmolarity activating transcription) to made the bacteria gathering. 3.3 Sweet Gene Sweet genes is the part that has positive affection to the multiplication of bacteria to help conceal and spread the death genes. We use molecule chaperone groE(K873000) which is found in many bacteria as the sweet genes cause it is required for proper folding of many proteins. 3.4 Undamental Conjugation Device The whole system relays on this part to transfer through conjugation. Among the part, J01003 is the key gene to be mobilized by R plasmid and we just add the I13521(RFP reporter) to test the mobility. 3.5 Death Genes We are glad to find and use the ready-made parts that satisfied our requirements. K117010 can produce lysis protein which has the fatal impact on bacteria, meanwhile, the promoter of the part be induced by AI-2 has the detection system to make the suicide process more intelligent. What’s more, it provides the opportunity to set the threshold of the bacteria count.
4 Bdellovibrio Detector(Dog Eat Dog System)The second method derives from the idea of cannibalism, we settle on a Bdellovibrio bacteriovorus strain, who lived in cracking other bacteria. We consider to reconstruct the chemotaxis of Bdellovibrio bacteriovorus，which leads to some sort of special chemotaxis action，and then improves the sterilization efficiency to a certain bacteria. Besides due to the special sterilization of Bdellovibrio bacteriovorus that can decompose the genetic material of the target bacteria, it can diminish the probability of bacteria resistance at the same time.
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