Team:Heidelberg/Delftibactin/DelRest

From 2013.igem.org

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                                   <h1>Week 13</h1>
                                   <h1>Week 13</h1>
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In the previous week several of the new primers improved our PCRs for DelO-P slightly. Nevertheless results were not convincing enough to use the amplified fragments for Gibson Assembly. The same encounted for the amplification of DelF-G. Here various strategies where conducted. Though none of these led to an entirely satisfying ampl of the genes DelF and DelG, we were able to amplify regions of the Delftibactin cluster which we could not amplifý with the initial primers. Therefore this week will be used for optimization of these PCRs as well as for validation of the amplicons we were already able to obtain in well established amplifications. Validation will be carried out with various restriction digests. PCR products showing positive digests will be prepared for single read sequencing to validate constructs before Gibson Assembly.
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In the previous week several of the newly ordered primer pairs improved our PCRs for DelO-P and DelF-G. Nevertheless results were not convincing enough to use the amplicons for Gibson Assembly. Therefore we spend this week optimizing the PCRs for the abovementioned fragments. In addition we validated the amplicons for
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already successfully optained last week by restriction digest.
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                                   <h1>Week 14</h1>
                                   <h1>Week 14</h1>
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Since last weeks aims beeing amplification of the missing fragments within the sequence region of DelF to DelG as well as amplification of DelO-P did not succeed and validations of all PCR products failed, this weeks goals are identical to those of the previous week. Additionally to the aim of amplifying the missing fragments, restriction digests of the successfully amplified fragments will be carried out using higher amounts of DNA. Furthermore samples of these PCRs will be prepared for single read sequencing.
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We were still struggeling with getting the correct amplicons for the fragments encoding DelFG as well as DelO-P.   Furthermore the restriction digests of the already successfully amplified fragments need to be repeated using higher amounts of DNA, as results of the previous test digests were rather inconclusive. Furthermore samples of these fragments will be send for single read sequencing.
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                                   <h1>Week 15</h1>
                                   <h1>Week 15</h1>
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Single read sequencing carried out by GATC and consequent alignment of the sequencing results obtained from <i>D. acidovorans</i> DSM-39 against the reference Sequence of <i>D. acidovorans SPH-1</i> (6.8 Mbp, NCBI Genome) revealed significant differences between the two strains of <i>D. acidovorans</i>. As result of this sequence analysis, the strain D. acidovorans SPH-1 was ordered from the DSMZ to have the suitable template for the primers we designed so far. Furthermore this should avoid issues which might occure in the Gibson Assembly in case mismachtes in the primers to the sequence of DSM-39 are present. Consequently all amplifications carried out before week 15 have to be repeated, conditions of the establihsed PCRs will be maintained, conditions for the missing fragments will be further optimized.
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Single read sequencing of the fragments
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Afterwards all the PCR amplicon will be validated by restriction digests and single read seqencing.
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was carried out by GATC. We blasted the obtained seqeuences against the reference sequence of <i>D. acidovorans SPH-1</i> available on NCBI. Although our sequence matched to the reference sequence, we found a significant number of missmatches, which was too diverse and high to be simply explained by mutations introduced by our polymerase during PCR (note: we used a high-fidelity proofreading polymerase suitable for GC-rich templates and long amplicons). We thus hypothesized that the SPH-1 strain based on which our cloning strategy was designed might have a significant number of single-nucleotide polymorphisms in the Del cluster when compared to the <i>D. acidovorans</i> DSM-39 strain, which we use as template for the PCRs (note: there is no complete genomic sequence available for the DSM-39 strain on NCBI). We further hypothesized, that this difference in sequence between the DSM-39 strain used as PCR template and the SPH-1 strain based on which our primers were designed could explain our troubles with the PCR amplifications of DelFG and DelOP. In consequence, we ordered the SPH-1 strain from the DSMZ to have the suitable template for our PCRs. This solved all our PCR problems right away and we were able to get all amplicons required for cloning the DelRest construct. Furthermore, we successfully validate our amplicons by restriction digest ans sequencing.  
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                                   <h1>Week 16</h1>
                                   <h1>Week 16</h1>
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Last week we successfully amplified all the desired genes from the Delftibactin cluster of <i>D. Acidovorans </i> SPH-1.
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Last week we successfully amplified all the fragments needed to complete the DelRest cloning. Therefore, we went ahaed and performed Gibson assembly in order to construct the final pFSN plasmid carrying the DelRest genes. The assembly mix was transformed into DH10beta electrocompetent cells. Screening PCRs showed that the assembly was successful, calling for futher validation of the clones.
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The recently obtained strain indeed, improved our PCRs significantly. Furthermore we were able to validate our amplicons with restriction digests. Therefore this weeks goal will be the cloning of our final pFSN plasmid using Gibson Assembly. Afterwards DH10B cells will be transformed with our plasmid by electroporation. Screening PCRs, test restriction digests and sequencings will be conducted to validate the final construct. Afterwards plasmids will be preped for further use and glycerol stocks of DH10B-pFSN will prepared for further storage.
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                                   <h1>Week 17</h1>
                                   <h1>Week 17</h1>
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Since we were able to rescue 3 candidate plasmids, from colonies which were positive for screening, by the end of last week. This week further colony PCRs, test restriction digests and sequencings will be conducted to validate the final construct. Initially we are going to focus on the plasmid from clone D8w, as preps of this clone are already available.
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From colonies which were positive for screening last week, we rescued 3 plasmids. Test restriction digest and sequencing was conducted to validate the constructs.  
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Consequently our screening primers will be used to check whether all fragments used in the Gibson Assembly are present in the final vector as well as to sequence the relevant ligation sites for any mutations that might have occured during primer synthesis or assembly.
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Afterwards plasmids will be preped for further use and glycerol stocks of DH10B-pFSN will be made.
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                                   <h1>Week 18</h1>
                                   <h1>Week 18</h1>
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All sequencings initialized last week were positive for the ligation sites within the insert including the genes DelA to DelF, DelO-P and DelL, only for the mRFP a mutation was detected. As sequencing results for this particular region, were not absolutly reliable, sequencing will be repeated this week, and analyis for functionality of mRFP will carried out by FACS. Furthermore a SDS page will be conducted to investigate the expression of our target genes.
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All sequencings carried out last week were positive. As it would be quite costly to sequence the whole 32 kb plasmid, we focused on the ligation site between the different assembly fragments, which are most prone to insertion of errors. All insert fragments sequenced, including the ligation sites between DelA and DelF, DelO-P and DelL, were 100 % correct. However, me detected a mutation within the mRFP cds. As sequencing results for this particular region, were not absolutly reliable (generally week signal in the chromatogramm), sequencing was repeated. FACS analysis of <i> E. coli </i>  bearing the DelRest construnct confirmed that mRFP was not expressed, likely due to the observed mutation. However, as mRFP was only meant to be an expression control for the DelRest genes, we did not see the need of going through the hazzle of removing this mutation - which would actually have been very challenging to do on such a big plasmid. Instead, we started preparing samples for an SDS page will in order to confirm the succesfful expression of the Del genes.
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                                   <h1>Week 19</h1>
                                   <h1>Week 19</h1>
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As the SDS page we carried out last week, did not display all expected bands absolutely certain, probably due to the very low amount of protein loaded, this SDS page will be repeated within week 19. Nethertheless most resources of the DelRest group will from now on be shifted to the cloning of DelH.
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As the SDS page we carried out last week, did not display all expected bands clearly, which was likely due to probably due to the very low amount of protein loaded, this SDS page will be repeated within week 19. Nethertheless most resources of the DelRest group will from now on be shifted to the cloning of DelH.
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Revision as of 21:01, 2 October 2013

Del Rest. Creating a 32 kbp plasmid.

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