Team:Brown/Project/Analysis

Optical Density

Optical Density WRT Time

Optical Density WRT Time

• Due to the nature of the Cell Lysis Cassette, Optical Densities can be used to determine when lysis has occurred. The R gene (endolysin) of the cassette degrades the cell wall. The solution becomes clear after lysis. After two to three hours, the Optical Density of the cell cultures dropped, signifying the expression of the S,R,Rz genes. The following graphs exhibit optical density trends during gene expression and resulting cell lysis and cell wall degradation. The first graph shows Optical Density as well as expected Resistance changes, which mirror Optical Density measurements. Resistance and Optical Density is expected to increase slightly within the first hour due to the continued cell growth after induction by .2% Arabinose.

Each culture was originally grown into the stationary phase and then diluted to the mid-log phase. The E. coli cells experience greatest growth in the Mid-Log phase. Arabinose was added while cells were in this phase which provided the quickest protein expression and resulting lysis.

NaCl Testing

• Multiple "Salt Tests" were performed to determine the exact sensitivity of our apparatus.

Salt concentrations originally tested are listed below. Further tests are to be run where the greatest resistance jump occurred to determine the exact concentration needed to see a significant resistance decrease due to cell lysis. Molarity (M):

1. .000005
2. .00001
3. .00005
4. .0001
5. .0005
6. .001
7. .005
8. .01
9. .05
10. .1

Resistance Testing

• This test was done with 50X concentrated pVJ4 E. coli bacteria resuspended in M9 Minimal Media. Cultures were left overnight.

Conductivity Testing

• Different from expected resistance measurements, the conductivity of the lysed solutions greatly increased. Initial conductivity tests were run one after the other due to the limited availability of conductivity probes. Team Toxipop now has access to two probes.