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• The interna)onal Gene)cally Engineered Machine (iGEM) compe))on – Annual worldwide Synthe)c Biology compe))on for undergraduate university students organized by MIT (Boston)
• The aim: – Build “simple” biological systems from standard, interchangeable parts (Biobricks) and operate them in living cells
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Our Goal To build a biological system that can facilitate the degrada)on of hydrocarbons (oil) in an
aqueous environment
Why? Examples:
• Clean up aMer an oil spill (Gulf of Mexico)
• Trea)ng waste water from Oil Sands extrac)on process (Canada)
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Our Plan Create biobricks, which will facilitate & standardize the following in E.coli:
1. Hydrocarbon • Degrada)on (alkanes) • Sensing • Tolerance
2. Salt tolerance 3. Emulsifier produc)on 4. Modeling (MFA)
Time Frame: Deadline: October 2010
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Hydrocarbon Degrada)on Aerobic oxida)on of alkanes
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Step 1: • C5-‐13 alkanes or C5-‐8 Cycloalkanes
• AlkB from Gordonia sp. • membrane protein • Has been expressed and fully
characterized (in vivo) in E.coli • Fujii et al. (2004) [1]
• C15-‐36 alkanes • LadA from G. thermodenitrificans • Uses Flavin Mononucleo)de (FMN)
complex • Li et al. (2008) [2]
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Hydrocarbon Degrada)on Aerobic oxida)on of alkanes
Step 2: • Alcohol Dehydrogenase (ADH)
• Bacillus thermoleovorans • Expressed and tested with C16 in
E.coli
• Kato et al. (2001) [3]
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Hydrocarbon Degrada)on Aerobic oxida)on of alkanes
Step 3: • Aldehyde Dehydrogenase (ALDH)
• Also from Bacillus thermoleovorans • C2-‐14 and most probably even higher
• Has been expressed and characterized in E.coli
• Kato et al. (2010) [4]
Step-‐by-‐step
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DNA Synthesis Biobrick assembly Transform E.coli K12
Characteriza)on
* Depending on what concentra)ons are quan)fiable by GC
Shake flask cul)va)on with low concentra)ons* of
hydrocarbons
-‐ Shorter chain (C8) -‐ Middle chain (C12, C11) -‐ Longer chain (C16, C17) -‐ Long chain (C20) -‐ Mixture
Transformed and non-‐transformed E.coli (nega)ve control)
In vitro enzyme assays SDS PAGE
GC Analysis
Hydrocarbon sensing
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From Pseudomonas pu>da:
From: [5] F. Rojo (2009) Degrada)on of alkanes by bacteria. Environmental Microbiology 11(10): 2477-‐2490
• In the presence of alkanes(C5-‐10) AlkS ac)vates expression of its own gene
• High AlkS levels ac)vate the PalkB promoter and expression of the alkBFGHJLK operon
Hydrocarbon tolerance
• Expression of chaperone prefoldin[6]
– Helps with folding process of proteins
– Simple: • only 1 gene • has already been expressed in E.coli
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[6] Okochi et al. (2008) Overexpression of prefoldin from the hyperthermophilic archaeum Pyrococcus horikoshii OT3 endowed E. coli with organic solvent tolerance. Applica>on of Mcrobial Biotechnology 79:443-‐449
Structure of prefoldin. Source: hlp://www.pdb.org
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Salt Tolerance
• Salinity in sea waters – 97% of salt in seawater: NaCl – Average salinity: 3.5% = 0.6M
• E.coli’s exis)ng tolerance: – 0.5M NaCl is inhibitory to growth
– ≥0.75M NaCl no growth
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BBC1 • Gene from Chlamydomonas (green
algae)
• Grants increased salt and temperature resistance
• Has been expressed and characterized in E.coli
• Salt tolerance increased up to 5% (0.86M)
• Increased survival aMer mul)ple -‐80°C (3 hour) shocks.
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From: [7] S. Tanaka (2000) Enhanced Tolerance Against Salt-‐Stress and Freezing-‐Stress of E.coli Cells expressing Algal bbc1 Gene. Current Microbiology 42: 173-‐177
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Emulsifier Produc)on
• Oil degrading organisms secrete emulsifiers
• Possible emulsifiers: – Homologs of E.coli OmpA [8]
• Acinetobacter V-‐26 AlnA (37 kDa) • Acinetobacter ADP1 AlnA (37 kDa)
– P. pu>da OprG [9] (24 kDa) • All have been cloned in E. Coli and shown to emulsify, although not clear whether they are excreted or not
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[8] G. Walzer et al. (2006) The Acinetobacter outer membrane protein A (OmpA) is a secreted emulsifier. Environmental Microbiology 8(6): 1026–1032 [9] G. Walzer et al. (2009) Iden)fica)on of outer membrane proteins with emulsifying ac)vity by predic)on of β-‐barrel regions. Journal of Microbiological Methods 76: 52–57
Topology sketch of amino acids 1–171 of AlnA as viewed from the barrel exterior[9]
Expression & Analysis
• Expression using a cons)tu)ve promoter • Characteriza)on – SDS PAGE analysis – Emulsifica)on tests (height tests) with cell-‐free supernatant, resuspended cells and lysed cells
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Modeling
• Metabolic Flux Analysis (MFA) – Op)mized produc)on pathways of profitable products such as PHA and CH4
• Modeling of regulatory mechanisms (such as hydrocarbon sensing by AlkS)
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To wrap it all up • Build biobricks for 3 subparts: – Hydrocarbon • Degrada)on: AlkB, LadA, ADH & ALDH • Sensing: AlkS, PalkS1, PalkS2 & PalkB
• Tolerance: Prefoldin
– Salt tolerance: BBC1
– Emulsifier produc)on: AlnA & OprG
• Implement and test in E.coli K12 strain
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Thank you for your )me Any ques)ons or remarks?
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References • [1] Fujii et al. (2004) Biotransforma)on of various alkanes using the Escherichia coli expressing an
alkane hydroxylase system from Gordonia sp. TF6. Bioscience, biotechnology, and biochemistry 68 (10): 2171-‐2177
• [2] L. Li et al. (2008) Crystal structure of long-‐chain alkane monooxygenase (LadA) in complex with coenzyme FMN: unveiling the long-‐chain alkane hydroxylase. Journal of molecular biology 376: 453–465
• [3] Kato et al. (2001) Gene Cloning of an Alcohol Dehydrogenase from Thermophilic Alkane-‐Degrading Bacillus thermoleovorans B23. Journal of Bioscience and bioengineering 91(1): 100-‐102
• [4] Kato et al. (2010) Gene cloning and characteriza)on of an aldehyde dehydrogenase from long-‐chain alkane-‐degrading Geobacillus thermoleovorans B23 Extremophiles 14: 33–39
• [5] F. Rojo (2009) Degrada)on of alkanes by bacteria. Environmental Microbiology 11(10): 2477-‐2490
• [6] Okochi et al. (2008) Overexpression of prefoldin from the hyperthermophilic archaeum Pyrococcus horikoshii OT3 endowed Escherichia coli with organic solvent tolerance. Applica>on of Mcrobial Biotechnology 79:443-‐449
• [7] S. Tanaka (2000) Enhanced Tolerance Against Salt-‐Stress and Freezing-‐Stress of E.coli Cells expressing Algal bbc1 Gene. Current Microbiology 42: 173-‐177
• [8] G. Walzer et al. (2006) The Acinetobacter outer membrane protein A (OmpA) is a secreted emulsifier. Environmental Microbiology 8(6): 1026–1032
• [9] G. Walzer et al. (2009) Iden)fica)on of outer membrane proteins with emulsifying ac)vity by predic)on of β-‐barrel regions. Journal of Microbiological Methods 76: 52–57
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