Part:BBa_M50050:Experience

General Information

Applications of BBa_M50050

• Standardized growth control for bacteria species that have pathways for sensing and responding to Autoinducer-2.

Stanford Location

Plasmid Name: LuxS Synthase Plasmid

DNA 2.0 Gene #: pD441-CH

Organism: E. coli

Device Type: Actuator

Glycerol Stock Barcode: 0133027189

Box Label: BIOE44 F16

Data

Figure 1: Images of the Western Blot with BBa_M50050(Sections A and B) compared to wild-type control (Sections C and F

Figure 2: Graph of the growth curves based on optical density readings at 600 nm over time of the LuxS transfected E. coli strain and the Cupid Pink (Pink) control strain at two different induced IPTG concentrations. A) Strains were induced at an in-solution IPTG concentration of 0 μM IPTG B) Strains were induced at an in-solution IPTG concentration of 1000 μM IPTG

Figure 3: Graph of the growth rate based on the change optical density readings at 600 nm over time of the LuxS transfected E. coli strain and the Cupid Pink (Pink) control strain at two different induced IPTG concentrations. A) Strains were induced at an in-solution IPTG concentration of 0 μM IPTG B) Strains were induced at an in-solution IPTG concentration of 1000 μM IPTG

Data Analysis and Conclusions

All figures show comparisons between the LuxS transfected bacteria, a wild-type control strain, and a similar IPTG-inducible E. coli strain with a T5 promoter (Pink).

Western Blot

Based on our analysis of our Western blot, we concluded that we were successful in transfecting our E. coli strain with the correct plasmid and gene sequence. For BBa_M50050, we looked at well sections A and B (BBa_M50050 transfected E. coli at 0 μM and 1000 μM in-solution concentration respectively) compared to the wild-type controls (C and F). What we see is that there are bands of proteins located at the 40 kilodaltons (the anticipated length) in sections A and B, but not in the control sections C and F.

Cell Density Tests

Based on the data collected from our overnight cell density tests, we can conclude that the over-expression of LuxS increases cell growth during the exponential growth phase, but does not result in any vastly different final cell density concentrations.

Experimental Procedures

Western Blot

Western Blots were performed on transformed bacteria to verify the expression of LuxS and LsrR, and on the untransformed E. coli cells, control, to account for any background. To do so, cultures of each strain were grown overnight at 37oC and split into two aliquots, each induced with either 0 μM and 1000 μM IPTG. Samples were then taken at 0, 4, 6, and 22 hours post-induction to measure the protein levels over time. To normalize the protein levels, 8*108 cells were taken from each samples, and the samples were immediately pelleted and frozen to prevent the cells from synthesizing anymore. After the samples have been collected, the bacteria were lysed with 10% SDS and boiled at 100oC for 10 minutes to denature the proteins. Sodium dodecylsulfate polyacrylamide gel electrophoresis was performed on the samples to separate the proteins based on molecular weight. The proteins were transferred onto a PVDF membrane and blocked with Pierce Fast Block for 5 minutes to stop nonspecific interactions and probed with anti-his antibody diluted at 1:1000 in Blotto for 1 hour. Afterwards the membrane was washed with TBS for 5 minutes three times and incubated in the 1:1000 goat-anti-mouse HRP conjugated secondary antibody. A 1:10 dilution of chromogenic substrate, Opti-4CN was then added and then membrane was imaged.

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