Difference between revisions of "Part:BBa K802004"

Revision as of 20:08, 25 September 2012

Shuttle vector for E. coli and B. subtilis

The shuttle vector of 6,5kb is Ampicillin resistant in E. coli and Erythromycin resistant in B. subtilis. It is a high plasmid copy number in both B. subtilis and E.coli. It has a polylinker containing all 4 of the iGEM sites.

Characterization

Transformation yield

In the NM522 E.coli strain the average yield was 3,3XE06 cells/µg.The transformed cells were selected on LB media supplemented with Ampicillin at a concentration of 100µg/mL.

In the BS168 B.subtilis strain the maximum yield was 70 cells/µg. The transformed cells were selected on LB media supplemented with Erythromycin at a concentration of 15µg/mL.

Antibiotic resistance

Given the fact that this shuttle vector is very similar to BBa_K802003, the two of them were tested in parallel. Two experiments were made in order to characterize the antibiotic resistance of the shuttle vectors: the first one on Agar plates and the second one in liquid cultures. In both cases the media was LB supplemented with Ampicillin at different concentrations.

The shuttle vector was transformed into the NM522 strain in order to be tested.

A) Agar plates
Saturated cultures containing the shuttle vectors were diluted 10, 100, 1000 and 10000 times. A volume of 5 µL of each solution containing the strain with the part BBa_K802003 (the saturated culture and the 2 diluted solutions) was deposed on the plate. The volume of the cultures containing the second shuttle vector (BBa_K802004) was adjusted in function of the OD in order to depose approximately the same number of bacterial cells.

As it can be seen in the picture, at 10 mg/mL (i.e. 100 times the usual selective concentration) there is bacterial growth, even for the culture diluted 10000 times (the corresponding inoculums is indicated by the number 4 written on the plates on the picture)

B) Liquid cultures

Multiple tubes containing LB media and Ampicillin at different concentrations ranging from 0 to 3 mg/mL are inoculated with bacteria containing the shuttle vectors BBa_K802003 and BBa_K802004 (or pBKL35 and pBKH36 in our collection). There were tested 3 per Ampicillin concentration for each vector. As a negative control a non resistant Ampicillin strain was used to inoculate a solution of LB media at the usual selective concentration of 100 µg/mL. The results are indicated below:

To sum up, there is no significant difference concerning the Ampicillin concentration tolerance between the two strains, therefore between the two shuttle vectors as far as E. coli strains are concerned. At 2,4 mg/mL there is no baterial growth for either strain.

The shuttle vector was transformed into the BS168 Bacillus subtilis strain in order to be tested.

A) Agar plates
Saturated cultures containing the shuttle vectors were diluted 100 and 10000 times. A volume of 5 µL of each solution containing the strain with the part BBa_K802003 (the saturated culture and the 2 diluted solutions) was deposed on the plate. The volume of the cultures containing the second shuttle vector (BBa_K802004) was adjusted in function of the OD in order to depose approximately the same number of bacterial cells.

As it can be seen in the picture, at 300 µg/mL there is bacterial growth, even for the culture diluted 10000 times (the corresponding inoculums is indicated by the number 4 written on the plates on the picture). However, for the strain containing the part BBa_K802003 at 300 µg/mL Erythromycin there can be noted a difference for all 3 inoculums compared to the first plate at 15 µg/mL, as opposed to the strain containing BBa_K802004 (where there is a notable difference only for the culture diluted 10000 times).

B) Liquid cultures

Multiple tubes containing LB media and Erythromycin at different concentrations ranging from 0 to 1,5 mg/mL are inoculated with bacteria containing the shuttle vectors BBa_K802003 and BBa_K802004 (strains BK49 and BK50 in our collection). After 20 hours of incubation at 37°C the OD600 of the cultures was measured at 600 nm. Afterwards, the OD value was converted in cfu/mL[1].The results are indicated below:

Sequencing of the modified regions

The two modified regions of the shuttle vector were verified by sequencing. The primers were designed using the sequences from the original plasmids that were used to construct the shuttle vector pHT315. The sequencing confirmed that the site SpeI was eliminated. However, there is still yet to confirm the iGEM polylinker, even though the gel electrophoresis confirmed the existence of all 4 of the iGEM sites.

Usage and Biology

It can be used to transform E. coli and Bacillus strains. However, it is highly recommended to amplify the plasmid before transforming a Bacillus strain because the transformation yield is low compared to E. coli.

Functional Parameters

The tests showed that in the NM522 E. coli strain there is bacterial growth in LB media having an Ampicillin concetration up to 1,2 mg/mL. Concerning the 168 B. subtilis strain, the bacteria transformed with this plasmid could be selected at Erythromycin concentrations as high as 1,2 mg/mL.

References

[1] http://bionumbers.hms.harvard.edu//bionumber.aspx?id=105453&ver=1