The iGEM Team of University of Southern Denmark 2012 igem.sdu.2012@gmail.com

Growth Curves

Inulin Staining

Growth curves: SST and FFT

Introduction:
This experiment was set up to measure the growth rates of our bacteria, expressing either of the two proteins fructan:fructan fructosyltransferase (FFT) and sucrose:sucrose fructosyltransferase (SST).
Our hypothesis is, that the growth of the bacteria producing the FFT will be as fast as the top 10 coli (because FFT shouldn't work without SST)and SST bacteria will be near the same speed (maybe a little slower because it converts the sucrose to 1-kestose).

Method:
In order to produce this growth curve we took E.coli top10 transformed with the pJET plasmid containing FFT or SST and grew them in 50 mL fresh LB medium (containing ampicillin).
We transfered 1 mL of overnight culture (ONC) to the fresh LB medium and measured the optical density (OD) at 600 nm, every hour.
We also made a negative sample containing 1 mL of ONC with E.coli top10 and 50 mL of LB media (without ampicillin)

Results:
The data is given in a table (table 1) and can also be seen plotted on a logarithmic scale (figure 1). Hour nr. 7 is left out, because it was measured at OD 450 instead of OD 600, hence giving false data.

Tabel 1
figure 1

Discussion:
As you can see, clearly, SST is decreasing the growth rate of the bacteria. This is most likely because SST produces an indigestible polysaccharide from sucrose, disabling the bacteria in getting the energy. FFT grows as fast as the negative test, which indicates that the protein does not have any disadvantages concerning growth. This is probably because FFT produces a trisaccharide from sucrose, that the bacteria is able to digest.

Conclusion:
SST is decreasing the growth rate of E. coli Top10 but not FFT.