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 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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In the previous week, several of the newly ordered primer pairs improved our PCRs for DelO-P and DelF-G. However, results were not convincing enough to use these amplicons for Gibson assembly. Therefore, we spend this week optimizing the PCRs for the abovementioned fragments. In addition we validated the amplicons for  
??? insert fragment names here ???  
??? insert fragment names here ???  
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                                   <h1>Week 14</h1>
                                   <h1>Week 14</h1>
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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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We were still struggeling with getting the correct amplicons for the fragments encoding DelF-G as well as DelO-P. Furthermore, the restriction digests of the already successfully amplified fragments needed to be repeated using higher amounts of DNA, as results of the previous test digests were rather inconclusive. Furthermore, samples of these fragments were send for sequencing.
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  ???? insert fragments here???  
  ???? insert fragments here???  
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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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was carried out by GATC. We blasted the obtained seqeuences against the reference sequence based on the <i>D. acidovorans SPH-1</i> strain 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 random 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 compared to the <i>D. acidovorans</i> DSM-39 strain, which we used as template for all 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 DelF-G and DelO-P. In consequence, we ordered the SPH-1 strain from the DSMZ in order to obtain a 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 within this week. Furthermore, we successfully validated our amplicons by restriction digest and sequencing.  
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                                   <h1>Week 16</h1>
                                   <h1>Week 16</h1>
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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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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 assembel the final pFSN plasmid carrying bearing the DelRest genes. The assembly mix was transformed into <i>E. coli DH10beta</i> electrocompetent cells. Screening PCRs showed that the assembly was successful, calling for futher validation of the clones.
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                                   <h1>Week 17</h1>
                                   <h1>Week 17</h1>
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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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From colonies which were positive for screening last week, we rescued 3 plasmids. Test restriction digest were conducted and showed our clones to be correct.
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                                   <h1>Week 18</h1>
                                   <h1>Week 18</h1>
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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 (note: we wanted to use mRFP in order to confirm expression from our plasmid). FACS analysis of <i> E. coli </i>  bearing the DelRest construnct showed that mRFP was not expressed, likely due to the corresponding mutation. However, as mRFP was only meant to be an expression control for the DelRest genes we did not start a mutagenesis in order to regain the correct mRFP cds. Instead, we started preparing samples for an SDS page in order to directly proof the expression of the Del genes by Coomassie staining.
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We send one of our most promising clones for sequencing. As it would be quite costly to sequence the whole 32 kb plasmid, we focused on the ligation sites between the different assembly fragments, which are most prone to insertion of errors. Although all insert fragments sequenced, including the ligation sites between DelA and DelF, DelO-P and DelL, were 100 % correct, wee detected a mutation within the mRFP cds (note: we wanted to use mRFP in order to confirm expression from our plasmid). FACS analysis of <i> E. coli </i>  bearing the DelRest construnct showed that mRFP was not expressed, likely due to the corresponding mutation. However, as mRFP was only meant to be an expression control for the DelRest genes we did not start a mutagenesis in order to regain the correct mRFP cds. Instead, we started preparing samples for an SDS page in order to directly proof the expression of the Del genes by Coomassie staining.
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Revision as of 21:44, 2 October 2013

Del Rest. Creating a 32 kbp plasmid.

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Methods: