Un juego de herramientas para la conversión de hidrocarburos en ambientes acuosos
Summary
Un auto sostenible sistema de regulación de las bacterias para la remediación de contaminaciones de aceite ha sido diseñado utilizando piezas estándar de ADN intercambiables (BioBricks). Una ingeniería<em> E. coli</emCepa> se utiliza para degradar alcanos a través de β-oxidación en ambientes acuosos tóxicos. Las respectivas enzimas de diferentes especies mostraron actividad de degradación de alcano. Además, una mayor tolerancia a<em> N</em>-Hexano se obtuvo mediante la introducción de genes de alcano bacterias tolerantes.
Abstract
Este trabajo expone un conjunto de herramientas que permite la conversión de alcanos por Escherichia coli y presenta una prueba de principio de su aplicabilidad. El juego de herramientas se compone de varias piezas estándar intercambiables (BioBricks) 9 abordan la conversión de alcanos, la regulación de la expresión génica y la supervivencia en tóxicos ambientes ricos en hidrocarburos.
Una vía de tres pasos para la degradación de alcano se llevó a cabo en E. coli para permitir la conversión de alcanos a medio y largo de cadena a sus respectivos alcanoles, alcanales y, finalmente, ácidos alcanoicos. Este último se metaboliza a través de la nativo β-oxidación vía. Para facilitar la oxidación de alcanos de cadena media-(C5-C13) y cicloalcanos (C5-C8), cuatro genes (alkB2, rubA3, rubA4 y Rubb) del sistema hidroxilasa alcano de Gordonia sp. TF6 8,21 se transformaron en E. coli. Para la conversión de losalcanos de cadena larga (C15-C36), el gen Lada de Geobacillus thermodenitrificans fue implementado. Para conocer los pasos necesarios adicionales del proceso de degradación, ADH y ALDH (procedente de thermodenitrificans G.) se introdujeron 10,11. La actividad se midió mediante ensayos de células en reposo. Para cada etapa oxidativa, la actividad enzimática se observó.
Para optimizar la eficacia del proceso, la expresión fue inducida sólo bajo condiciones bajas de glucosa: un promotor regulado sustrato, pCaiF, se utilizó. pCaiF está presente en E. coli K12 y regula la expresión de los genes implicados en la degradación de fuentes de carbono distintas a la glucosa.
La última parte del conjunto de instrumentos – focalización supervivencia – se implementó el uso de genes de tolerancia, solventes PhPFDα y β, ambos de Pyrococcus horikoshii OT3. Disolventes orgánicos pueden inducir estrés celular y la disminución de la supervivencia de forma negativa affecting plegamiento de proteínas. Como chaperones, PhPFDα y β mejorar el proceso de plegamiento de proteínas por ejemplo en virtud de la presencia de alcanos. La expresión de estos genes condujeron a una tolerancia mejorada de hidrocarburos se muestra por una tasa de crecimiento mayor (hasta 50%) en la presencia de 10% de n-hexano en el medio de cultivo se observaron.
En resumen, los resultados indican que el kit de herramientas permite E. coli para convertir y tolerar hidrocarburos en ambientes acuosos. Como tal, representa un primer paso hacia una solución sostenible para la recuperación de petróleo mediante un enfoque de la biología sintética.
Introduction
Oil pollution is among the most serious causes of environmental contamination, and greatly affects ecosystems, businesses and communities 3. Solutions are for example required to battle the continuous oil pollution originating from the oil sands tailing waters in Alberta, Canada. During the process of oil extraction from oil sands, bitumen, a semi-solid oxidized form of oil, is removed using thermal recovery techniques that consume about 3.1 barrels of water per single barrel of oil 1. Oil contaminated process water, mainly originating from a local river, is stored in tailing ponds after bitumen extraction. A more effective recycling of process water in order to reduce the need for freshwater uptake is needed. To facilitate the bitumen extraction and to ensure that downstream sites meet water quality guidelines for the protection of aquatic ecosystems, process water treatments are rapidly evolving 3.
To treat pollution of organic compounds, bioremediation technologies employing microorganisms are presently encouraged 1. Alkanes are the most abundant family of hydrocarbons in crude oil, containing 5 to 40 carbon atoms per molecule 7, 21. Many bacteria are known to degrade alkanes of various lengths via sequential oxidation of the terminal methyl group forming first alcohols, then aldehydes and finally fatty acids 8. Within this iGEM project several enzymes from different organisms were expressed and characterized, and made available via the BioBrick standard and Registry of Standard Biological Parts.
The well-studied alkane hydroxylase system of Gordonia sp. TF6 facilitates the initial oxidation step of C5-C13 alkanes along with that of C5-C8 cycloalkanes using a minimum of four components: alkB2 (alkane 1-monooxygenase), rubA3, rubA4 (two rubredoxins) and RubB (rubredoxin reductase) 8, 21. Oxidation of long-chain alkanes (ranging from C15 up to C36) is reported to be performed by ladA, a flavoprotein alkane monooxygenase from Geobacillus thermodinitrificans NG-80-2 7, 15, 18, 22. LadA forms a catalytic complex with flavin mononucleotide (FMN) that utilizes atomic oxygen for oxidation. This results in the conversion of alkanes into the corresponding primary alkanol. The alcohols are further oxidized by alcohol and aldehyde dehydrogenases to fatty acids, which readily enter the β-oxidation pathway 7, 21. A zinc-independent alcohol dehydrogenase from the thermophillic bacterium Geobacillus thermoleovorans B23 oxidizes medium-chain alkanols into their respective alkanals, using NAD+ as a cofactor 10. Aldehyde dehydrogenase from the same bacterium is able to catalyze the NAD+-dependent final step in the medium-chain oxidation 11.
In order to reduce induction costs and to maintain optimal proliferation of the bacterial system, the promoter pCaiF from E.coli was characterized. This promoter can regulate expression of the hydrocarbon degradation pathway components, and is regulated by cAMP-Crp levels, which in turn depend on glucose levels 6. At high extracellular glucose concentrations in the environment the cellular cAMP (cyclic Adenosine Mononucleotide Phosphate) level was low through the inhibition of adenylyl cyclase as a side effect of PTS mediated glucose transport. Conversely, during limitation (low glucose concentrations) the cAMP level increased and Crp bound to cAMP forming the complex, cAMP-Crp, which bound pCaiF and activated transcription of the downstream components 6, 14.
Wildtype E. coli can only tolerate moderate concentrations of hydrocarbons. To complete the toolkit, tolerance to hydrocarbons had to be addressed. Several organic solvent-tolerant bacteria are known to survive in water-solvent two-phase systems 12. Molecular components known to increase tolerance are chaperones that facilitate the correct folding of proteins. The prefoldin system from Pyrococcus horikoshii OT3, consisting of the proteins phPFDα and phPFDβ, was shown to increase hydrocarbon-tolerance 17.
The alkane conversion toolkit was constructed following the BioBrick principle, which is documented at the Registry of Standard Biological Parts 9. BioBricks are plasmids containing a specific functional insert that is flanked by 4 predefined restriction sites. The BioBrick inserts can be extended flexibly, allowing the construction of biological systems with new functions.
Protocol
Representative Results
Discussion
El principio BioBrick se utiliza para construir un chasis para la degradación de alcanos y una prueba de principio para los componentes individuales de la caja de herramientas se obtuvo. Se proponen varios ensayos para medir la in vivo e in vitro de la actividad de enzimas de la ruta de degradación de alcanos. El trabajo presentado con éxito demuestra un número de métodos que pueden utilizarse para determinar la actividad enzimática y la expresión en el organismo huésped E. coli despu?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
Los experimentos realizados en este video-artículo fueron desarrollados para la competición internacional Genetically Engineered Machine 9. Los autores desean agradecer a los miembros del equipo iGEM Lucas Bergwerff, Pieter van TM Boheemen, Cnossen Jelmer, Hugo F. Cueto Rojas y Ramón van der Valk para la asistencia en la investigación. Agradecemos Han de Winde, Stefan de Kok y Yıldırım Esengul útil para los debates y hosting esta investigación. Este trabajo fue apoyado por la TU Delft University Departamento de Biotecnología, el Laboratorio de Bioinformática Delft, TU Delft Departamento de Bionanoscience, Oil Sands Leadership Initiative (OSLI), Stud studentenuitzendbureau, la Iniciativa de Países Bajos Genómica, Centro Kluyver, Nederlandse Vereniging Biotechnologische (Stichting Biotecnología Nederland) , DSM, Geneart, Greiner Bio-One y Genencor.
Materials
| Name of the reagent | Company | Catalogue number | Comments (optional) |
| E. coli K12 | New England Biolabs | C2523H | |
| Octane | Fluka | 74822 | |
| Hexadecane | Fluka | 52209 | |
| octanol-1 | Fluka | 95446 | |
| dodecanol-1 | Sigma-Aldrich | 126799 | |
| Hexane | Sigma-Aldrich | 296090 | |
| NADH | Sigma | N4505 | |
| FMN | Sigma | F2253 | |
| MgSO4 | J.T. Baker Casno | 7487 889 | |
| Triton X-100 | Sigma-Aldrich | T8787 | |
| T4 ligase | New England Biolabs | M0202L | |
| Gas chromatograph | |||
| Cell disrupter | LA Biosystems | CD-019 | |
| Spectrophotometer | Amersham pharmacia | spec 2000 | |
| Plate reader | Tecan | Magellan v7.0 | |
| Incubator | Innova, 44 | ||
| BioBrick K398014: BBa_J23100-BBa_J61100-alkB2-BBa_J61100-rubA3-BBa_J61100-rubA4– BBa_J61100-rubB |
Delft University of Technology at the department of Biotechnology or Registry of Standard Biological Parts | BBa_K398014 | Alkane Hydroxylase System Resistance: Chloramphenicol |
| BioBrick K398027: BBa_R0040-BBa_B0034-ladA | Delft University of Technology at the department of Biotechnology or Registry of Standard Biological Parts | BBa_K398027 | ladA Protein Generator Resistance: Chloramphenicol |
| BioBrick K398018: BBa_J23100-BBa_J61101-ADH | Delft University of Technology at the department of Biotechnology or Registry of Standard Biological Parts | BBa_K398018 | ADH generator Resistance: Chloramphenicol |
| BioBrick K398030: BBa_R0040-BBa_B0034-ALDH | Delft University of Technology at the department of Biotechnology or Registry of Standard Biological Parts | BBa_K398030 | ALDH generator Resistance: Chloramphenicol |
| BioBrick K398326: pCaiF | Delft University of Technology at the department of Biotechnology or Registry of Standard Biological Parts | BBa_K398326 | pCaiF promoter Resistance: Chloramphenicol |
| BioBrick K398331: pCaiF-BBa_B0032-BBa_I13401 | Delft University of Technology at the department of Biotechnology or Registry of Standard Biological Parts | BBa_K398331 | pCaiF measurement device Resistance: Chloramphenicol |
| BioBrick K398406: BBa_J23002-BBa_J61107-phPFDα-BBa_J61107- | Delft University of Technology at the department of Biotechnology or Registry of Standard Biological Parts | BBa_K398406 | Solvent tolerance cluster Resistance: Chloramphenicol |
References
- Allen, E. W. Process water treatment in Canada’s oil sands industry: I: Target pollutants and treatment objectives. J. Environ. Eng. Sci. 7, 123-138 (2008).
- Alon, U. . An Introduction to Systems Biology: Design Principles of Biological Circuits. , (2007).
- Center, O. P. . Understanding Oil Spills and Oil Spill Response. , (1999).
- Eichler, K., Buchet, A., Lemke, R., Kleber, H. P., Mandrand-Berthelot, M. A. Identification and characterization of the caiF gene encoding a potential transcriptional activator of carnitine metabolism in Escherichia coli. J. Bacteriol. 178, 1248-1257 (1995).
- Feng, L., Wang, W., Cheng, J., Ren, Y., Zhao, G., Gao, C., Tang, Y., Liu, X., Han, W., Peng, X., et al. Genome and proteome of long-chain alkane degrading Geobacillus thermodenitrificans NG80-2 isolated from a deep-subsurface oil reservoir. Proc. Natl. Acad. Sci. U.S.A. 104 (13), 5602-5607 (2007).
- Fujii, T., Narikawa, T., Takeda, K., Kato, J. Biotransformation of various alkanes using the Escherichia coli expressing an alkane hydroxylase system from Gordonia sp. TF6. Biosci. Biotechnol. Biochem. 68 (10), 2171-2177 (2004).
- Kato, T., Miyanaga, A., Haruki, M., Imanaka, T., Morikawa, M., Gene Kanaya, S. cloning of an alcohol dehydrogenase from thermophilic alkane-degrading Bacillus thermoleovorans B23. J. Biosci. Bioeng. 91 (1), 100-102 (2001).
- Kato, T., Miyanaga, A., Kanaya, S., Morikawa, M. Gene cloning and characterization of an aldehyde dehydrogenase from long-chain alkane-degrading Geobacillus thermoleovorans B23. Extremophiles. 14, 33-39 (2010).
- Kieboom, J., De Bont, J. a. M. . Bacterial Stress Responses. , (2000).
- Kotte, O., Zaugg, J. B., Heinemann, M. Bacterial adaptation through distributed sensing of metabolic fluxes. Mol Syst Biol. 6, 355 (2010).
- Kremling, A., Bettenbrock, K., Gilles, E. D. Analysis of global control of Escherichia coli carbohydrate uptake. BMC Syst. Biol. 1, (2007).
- Li, L., Liu, X., Yang, W., Xu, F., Wang, W., Feng, L., Bartlam, M., Wang, L., Rao, Z. Crystal structure of long-chain alkane monooxygenase (LadA) in complex with coenzyme FMN: unveiling the long-chain alkane hydroxylase. J. Mol. Biol. 376 (2), 453-465 (2008).
- Lin, H. Y., Mathiszik, B., Xu, B., Enfors, S. O., Neubauer, P. Determination of the maximum specific uptake capacities for glucose and oxygen in glucose-limited fed-batch cultivations of Escherichia coli. Biotechnol. Bioeng. 73 (5), 347-357 (2001).
- Okochi, M., Kanie, K., Kurimoto, M., Yohda, M., Honda, H. Overexpression of prefoldin from the hyperthermophilic archaeum Pyrococcus horikoshii OT3 endowed Escherichia coli with organic solvent tolerance. Appl. Microbiol. Biotechnol. 79 (3), 443-449 (2008).
- Rehm, H. J., Reiff, I. Mechanisms and occurrence of microbial oxidation of long-chain alkanes. Adv. Biochem. Eng. / Biotechnol. 19, 175-215 (1981).
- Rojo, F. Degradation of alkanes by bacteria. Environ. Microbiol. 11 (10), 2477-2490 (2009).
- Van Beilen, J. B., Panke, S., Lucchini, S., Franchini, A. G., Rothlisberger, M., Witholt, B. Analysis of Pseudomonas putida alkane-degradation gene clusters and flanking insertion sequences: evolution and regulation of the alk genes. Microbiology. 147, 1621-1630 (2001).
- Wang, L., Tang, Y., Wang, S., Liu, R. L., Liu, M. Z., Zhang, Y., Liang, F. L., Feng, L. Isolation and characterization of a novel thermophilic Bacillus strain degrading long-chain n-alkanes. Extremophiles. 10 (4), 347-356 (2006).
