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Revision as of 15:33, 26 September 2011
TITLE = Genomic Library Expression |
BODY =
PROJECT/SUBPROJECT FOCUS
Making a genetic tool/plasmid to make a genomic and plasmid library of P. putida.
Project Participants
Peter Qi, Saeed Qureshi
July 7-14th, 2011
Author: Peter Qi
Miniprepped the B0015 plasmid (iGEM) from overnight cultures in LB/AK. Plasmid yield is acceptable, with relatively high purity in most samples. The plasmids are cut with EcoRI and blunted ended with T4 polymerase. A streak plate (Gent15) of the pUCP30T backbone was acquired from the Schryvers lab glycerol stocks, and overnight cultures were made to collect the backbone plasmid. The yield was high with good purity. pUCP30T plasmid DNA was digested with SfiI with recommended reaction conditions, and frozen/stored at -20C, to stop but not inactivate the SfiI enzyme. Further cloning steps to be continued in the next week.
July 14-21st, 2011
Author: Peter Qi
Cleaned up SfiI restriction digest reaction with PCR purification kit, and measured DNA concentration on Nanodrop, the concentration was low, but the purity was relatively high for most samples. The product is the pUC30T plasmid cut and blunt-ended (still 1 linear piece of DNA).
Blunt ended the products of B0015 (iGEM plasmid) EcoRI digest, and blunt-ended by T4 reaction, the products subsequently purified by gel extraction. Concentration measured as before, but is too low and impure. However, it is acceptable to use these samples to do the ligation step with product from above, introducing the T7 double terminator in B0015 into the pUCP30T backbone.
Plasmid DNA was prepared from overnight P. putida cultures, two preps were made. A genomic prep was made as well. The plasmid prep samples contained high nucleotide concentration, but is likely contaminated with RNA, confirmed by RNase treatment results. There is also a large amount of undissolved material, which is likely RNA. The genomic prep yielded little DNA. Once all samples are properly solubilized, they will all be treated with RNase, and concentration measured. The DNA prepared here is for the genomic and plasmid promoter libraries, which can start once all DNA are collected.
More plasmid DNA of the parts to be cloned will be prepped, since low DNA concentration has been an issue. The pUCP30T-ter plasmid should constructed and transformed next week.
July 21st-28th
Author: Peter Qi
Performed 10 minipreps each for the B0015 and pUCP30T plasmid, and DNA/nucleotide concentration of each prep is measured on Nanodrop. All B0015 preps are digested with EcoRI for 2 hours, while all pUCP30T preps are digested with SfiI for 2 hours. The pUCP30T digest is purified using a PCR purification kit, with modification to the original protocol (see list of protocols). All digests are blunt-ended by Invitrogen T4 DNA polymerase, and purified again using PCR purification. The purified blunt-end fragments are all digested in PstI for 2 hours, and run on a 1% agarose gel for electrophoresis. The proper fragments from pUCP30T (~4.1kb) is isolated using Qiagen gel extraction kit. The fragment from the B0015 plasmid (129kb) was lost due to over elution. The B0015 fragment will be recovered again next week using a 1.5% agarose gel, and a ladder appropriate for its size. Gel extraction protocols will also be refined to give higher and purer yields of cloned parts.
July 28th – Aug 5th, 2011
Author: Peter Qi
OBJECTIVES:
- To purify the B0015 part (T7 double terminator element, 129bp) from restriction digests.
- Ensure that the B0015 terminator part is flanked by one sticky end made by PstI, and a blunt ended with a poly-A tail.
- To purify the pUCT30T plasmid (-lacZ a) from restriction digests.
July 28th – Aug 5th, 2011
SUMMARY OF ACTIONS TAKEN
For objectives #1 and #2:- Restriction digest of 10µg of B0015 plasmid DNA by EcoRI (incubation at 37C for 2 hrs, inactivate enzyme by incubation at 80C for 20min).
- Blunt end the restriction digest products using NEB T4 DNA polymerase.
- Use Qiagen PCR purification kit to remove T4 DNA polymerase and nucleotides (dNTPs)
- Added a poly-A tail to the blunt ends.
- Restriction digest of 10µg of pUCP30T plasmid DNA by SfiI (incubation at 50C for 2 hrs, remove enzyme by PCR purification).
- Blunt end the restriction digest products using NEB T4 DNA polymerase.
- Use Qiagen PCR purification kit to remove T4 DNA polymerase and nucleotides (dNTPs)
- Added a poly-T tail to the blunt ends.
RESULTS:
Purified results show 50-60% yields from PCR purifications at the end of step 3 (for both sections), or approximately 5 µg of DNA.
INTERPRETATION
The amount of DNA retrieved after each cloning step may be too little eventually to acquire enough DNA, especially for the B0015. Potentially, PCR amplification of the iGEM part (B0015) can provide enough DNA for cloning.
Aug 5th – Aug 12th, 2011
Author: Peter Qi OBJECTIVES:- Finish preparing B0015 and pUCP30T (without lacZa)
- Ligate the two fragments in objective 1.
Making a genetic tool/plasmid to make a genomic and plasmid library of P. putida.
REFERENCE:Aug 5th – Aug 12th, 2011
SUMMARY OF ACTIONS TAKEN
For objectives 1):
- Antarctic phosphatase treated the vector/pUCP30T (see protocol list for procedure)
For objectives 2):
- Set up 2 sets of ligation reactions, each with 3 different insert:backbone ratios (3:1, 1:1, 3:1) for overnight reactions.
- Ligations were transformed into DH5a competent cells found in BHSc freezer (-80C) from 2005.
- Plated transformations on LB+Gent15 plates with IPTG (100uL at 0.1M) and XGal (50uL at 10mg/mL).
RESULTS:
Transformations of the ligations showed a natural logarithm function of growth overnight, only white colony/growth is observed, no
INTERPRETATION
The transformation of the ligation mixture is likely not successful, because the gentamicin plates may not function properly, or the competent cells are not the right genotype or have lost competency. The gentamicin plates are tested with E. coli strains with amp resistance but not gentamicin resistance, and also Pseudomonas putida LD1 (not resistant to gentamicin), and both showed slight growth overnight, so new gent plates are needed. The competent cells can be tested by performing the appropriate controls (transforming plasmids with LacZ and other resistance markers).
DATE CREATED: Aug 12th – Aug 19th, 2011
Author: Peter Qi
OBJECTIVES: Prepare the LacZ part for the next step in the cloning procedure (to insert in to the pUCP30T vector without lacZa and B0015/double terminator inserted).
PROJECT/SUBPROJECT: Making a genetic tool/plasmid to make a genomic & plasmid library of P. putida.
REFERENCE: Aug 12th – Aug 19th, 2011
SUMMARY OF ACTIONS TAKEN
- Plated cultures of miniCTX2-pfad-LacZ from Tung’s group on LB+Tet15 plates.
- Made overnight cultures of colonies on the plate in LB+Tet15.
- Plasmid miniprep of the overnight cultures.
- NcoI digest for 2 hours (60uL rxns)
- Gel extraction of the ~7kb fragment using phenol/alcohol/alcohol extraction (see protocol list for procedure)
RESULTS:
Little DNA was isolated from the extraction process, shown by Nanodrop, also, the sample was unpure, likely contaminated from the reagents in the extraction in step 5)
INTERPRETATION
The method of gel extraction is likely not very effective, and a different approach may be needed to provide better results. Better yields are needed for better cloning results.
Aug 19th – Aug 24th, 2011
Author: Peter Qi
OBJECTIVES
- Repeat cloning steps summarized July 28th to Aug 5th for another ligation reaction with Saeed.
- Obtain more DNA for the second cloning step referred to in previous entry.
REFERENCE: Aug 19th – Aug 24th, 2011
WHAT DID YOU DO:
For objectives 1): See entry for Aug 5th-Aug 12th.
RESULTS:
After transformation using competent DH5a cells from Maggie’s lab collection on Gent20 plates (new) with IPTG and XGal (concentrations as before), numerous colonies grew overnight. Most colonies in the middle of the plates are blue, while the colonies on the border of the plate are slight blue or colorless. Repeat transformation using Top10 competent cells on IPTG and XGal gent20 plates give better results (i.e. white colonies in the middle of the plate).
INTERPRETATION
The competent cells from Maggie’s lab likely do not have the right genotype (i.e. they have a lacZ gene, rather than the ?M15 genotype, which does not have a lacZ), which explains why most colonies are blue. The colonies on the border are not white because the IPTG and XGal was not spread evenly on the border. White colonies in the repeated transformations using Top10 can be cultured overnight to test for the right genotype (by restriction digest). Saeed checked the colonies, but none seemed to have the right genotype. A new strategy will be developed by Saeed with Dr. Mayi and Maggie to ensure faster and more accurate cloning steps for the next week.
Aug 25th – Sep 1st, 2011
Peter was on break.
Sep 2nd, 8th, 9th, 2011
Author: Peter Qi
OBJECTIVES:
- Choose additional candidate genes for RT-PCR experiments (with NA treatment) from Pseudomonas.com searches.
- Help Saeed with assays of E. coli strains with IPTG-LacZ inserts with chlorophenolred-ß-D-galactopyranoside.
- Design RT-PCR experiments to check validity of primers, and design a new primer for the housekeeping gene (rpoD)
SUMMARY OF ACTIONS TAKEN
For objectives #1:
- Went over list of gene hits with Stephen to choose genes that maybe relevant for NA-response genes/promoters, by doing internet searches on gene function etc.
For objectives #2:
- Cultures of E. coli (with IPTG+LacZ plasmid) exposed to IPTG and CPRG were incubated at 37C.
- Every 30 minutes, a culture was spun down to remove the bacteria, and 200uL of the supernatant was measured in a plate reader to measure absorbance.
For objectives #3:
- Literature searches were conducted to search for housekeeping genes in Pseudomonas.
RESULTS:
- Objective 1: Found one gene that is relevant, named as a dioxygenase, and showed homology to ring-cleaving proteins
- Objective 2: See Saeed’s records for results.
- Objective 3: Found 1 housekeeping gene commonly used for Pseudomonas RT-PCR, rpoD, a sigma factor.
INTERPRETATION
The primers of the gene found in objective one needs to have primers designed to be included in RT-PCR experiment. The rpoD primer needs to be ordered.
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