Team:PennState/diauxie/progress

Each test construct (promoter + GFP) was cloned into the pSB1A2 plasmid and transformed into several E. coli strains: DH5α, W3110 ∆xylB-G, and W3110 ∆xylB-R. Preliminary induction studies were run to find the optimal induction time and to analyze the linear range for OD versus fluorescence.

Test Construct

Tests were then run to compare the levels of induction with various mixes of xylose, glucose and xylose+glucose. The goal was to obtain a noticeably higher level of induction with the xylose/glucose mixture when compared to the wild-type construct.

DH5a fluoresence

W3110 fluoresence

These graphs show the normalized fluoresence strength for PN, P1, and P3 xylose promoters induced with xylose, glucose, and a mixture. The W3110 cells have xylE and xylG knocked out while DH5a contains the natural E. coli chromosome. This data shows that there is little effect on the fluorescence intensity using strains with xylE and xylG sequences deleted. Our next step is to transform these promoters into E. coli cells with deleted xylose metabolism and transporters.

PN induction time

P1 induction time

P3 induction time

The cells were induced iduced with sugars and then allowed to grow with sample being removed every half hour. The goal was to find the induction time where fluorescence starts to level off. The intensity has leveled off and begins to drop after 7.5 hours so this was the growth time for all future tests.

PN linear range

P1 linear range

P3 linear range

The three promoters analyzed show linear behavior in the optical density range. The strength of fluorescence did change depending on the promoter. With this information we were able to accurately normalize fluorescence data.