Team:XMU-China/Project/Description

Project Description

i-ccdB: intelligent Control of Cell Density in Bacteria

We have developed a series of devices which program a bacteria population to maintain at different cell densities. We have designed and characterized the genetic circuit to establish a bacterial ‘population-control’ device in E. coli based on the well-known quorum-sensing system from Vibrio fischeri, which autonomously regulates the density of an E. coli population. The cell density however is influenced by the expression levels of a killer gene (ccdB) in our device. As such, we have successfully controlled the expression levels of ccdB by site-directed mutagenesis of a luxR promoter (lux pr) and error-prone PCR of gene luxR, and finally we have built a database for a series of mutation sites corresponding to different cell densities. An artificial neural network has then been built to model and predict the cell density of an E. coli population. This work can serve as a foundation for future advances involving fermentation industry and information processing.

Figure 1 The bacteria population-control device.

This circuit incorporates a mechanism for programmed death in respond to changes in the environment, and allows us to probe the design principles of its more complex natural counterparts.

reference

[1] Kempner E, Hanson F. Aspects of light production by Photobacterium fischeri[J]. Journal of Bacteriology, 1968, 95(3): 975-979.

[2] Fuqua WC, Winan SC, Greenberg E. Quorum sensing in bacteria: the luxR-luxI family of cell density-responsive transcriptional regulators[J]. Journal of Bacteriology, 1994, 176(2): 269-275.

[3] Baldwin T, Devine JH, Heckel, RC, Lin, JW, Shadel GS. The complete nucleotide sequence of the lux regulon of Vibrio fischeri and the luxABN region of Photobacterium leiognathi and the mechanism of control of bacterial bioluminescence[J]. Journal of Bioluminescence and Chemiluminescence, 1989, 4(1): 326-341.

[4] You L, Cox RS, Weiss R, Arnold FH. Programmed population control by cell-cell communication and regulated killing[J]. Nature, 2004, 428(6985): 868-871.

[5] Kampranis SC, Howells AJ, Maxwell A. The interaction of DNA gyrase with the bacterialtoxin CcdB: evidence for the existence of two gyrase-CcdB complexes[J]. Journal of Molecular Biology, 1999, 293(3): 733-744.