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Evaluation of promoters and ribosome binding sites for biotechnological applications in the unicellular cyanobacterium Synechocystis sp. PCC 6803
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.ORCID iD: 0000-0002-6413-1443
2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 36640Article in journal (Refereed) Published
Abstract [en]

For effective metabolic engineering, a toolbox of genetic components that enables predictable control of gene expression is needed. Here we present a systematic study of promoters and ribosome binding sites in the unicellular cyanobacterium Synechocystis sp. PCC 6803. A set of metal ion inducible promoters from Synechocystis were compared to commonly used constitutive promoters, by measuring fluorescence of a reporter protein in a standardized setting to allow for accurate comparisons of promoter activity. The most versatile and useful promoter was found to be PnrsB, which from a relatively silent expression could be induced almost 40-fold, nearly up to the activity of the strong psbA2 promoter. By varying the concentrations of the two metal ion inducers Ni(2+) and Co(2+), expression from the promoter was highly tunable, results that were reproduced with PnrsB driving ethanol production. The activities of several ribosomal binding sites were also measured, and tested in parallel in Synechocystis and Escherichia coli. The results of the study add useful information to the Synechocystis genetic toolbox for biotechnological applications.

Place, publisher, year, edition, pages
2016. Vol. 6, article id 36640
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:uu:diva-308074DOI: 10.1038/srep36640ISI: 000388069200002PubMedID: 27857166OAI: oai:DiVA.org:uu-308074DiVA, id: diva2:1049129
Funder
Swedish Energy Agency, 38334-1
Available from: 2016-11-23 Created: 2016-11-23 Last updated: 2018-01-07Bibliographically approved
In thesis
1. Metabolic Engineering of Synechocystis sp. PCC 6803 for Terpenoid Production
Open this publication in new window or tab >>Metabolic Engineering of Synechocystis sp. PCC 6803 for Terpenoid Production
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the Paris Agreement from 2015, nations agreed to limit the effects of global warming to well below 2°C. To be able to reach those goals, cheap, abundant and carbon neutral energy alternatives needs to be developed. The microorganisms that several billion years ago oxygenated the atmosphere; cyanobacteria, might hold the key for creating those energy technologies. Due to their capacity for photosynthesis, metabolic engineering of cyanobacteria can reroute the carbon dioxide they fix from the atmosphere into valuable products, thereby converting them into solar powered cell factories.

Of the many products bacteria can be engineered to make, the production of terpenoids has gained increasing attention for their attractive properties as fuels, pharmaceuticals, fragrances and food additives. In this thesis, I detail the work I have done on engineering the unicellular cyanobacterium Synechocystis sp. PCC 6803 for terpenoid production. By deleting an enzyme that converts squalene into hopanoids, we could create a strain that accumulates squalene, a molecule with uses as a fuel or chemical feedstock. In another study, we integrated two terpene synthases from the traditional medical plant Coleus forskohlii, into the genome of Synechocystis. Expression of those genes led to the formation of manoyl oxide, a precursor to the pharmaceutically active compound forskolin. Production of manoyl oxide in Synechocystis was further enhanced by engineering in two additional genes from C. forskohlii that boosted the flux to the product. To learn how to increase the production of squalene, manoyl oxide or any other terpenoid, we conducted a detailed investigation of each step in the MEP biosynthesis pathway, which creates the two common building blocks for all terpenoids. Each enzymatic step in the pathway was overexpressed, and increased flux was assayed by using isoprene as a reporter and several potential targets for overexpression were identified. The final part of this thesis details the characterization of native, inducible promoters and ribosomal binding sites in Synechocystis

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. p. 63
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1455
Keyword
Metabolic engineering, Cyanobacteria, Synechocystis, Terpenoids, Genetic tools
National Category
Biochemistry and Molecular Biology Microbiology
Research subject
Microbiology
Identifiers
urn:nbn:se:uu:diva-308099 (URN)978-91-554-9761-3 (ISBN)
Public defence
2017-01-13, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2016-12-20 Created: 2016-11-23 Last updated: 2016-12-28
2. Engineering cyanobacteria for increased growth and productivity
Open this publication in new window or tab >>Engineering cyanobacteria for increased growth and productivity
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Increasing the photosynthetic efficiency is one of the strategies to increase the crop yields to meet the requirement of 50% more food by 2050. Due to the similarity on photosynthesis between crops and cyanobacteria, cyanobacteria are ideal alternatives to study photosynthesis since cyanobacteria are prokaryotes, easier to engineer and have shorter life cycle. On the other hand, cyanobacteria are promising cell factories for food additives, biofuels, and other products. To get the desired products from cyanobacteria directly will consume atmospheric CO2 and avoid additional releasing of CO2 from the usage of fossil resources.

In this thesis, four CBB cycle enzymes were overexpressed individually in the model cyanobacterium Synechocystis PCC 6803. To get ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) overexpressed, two methods were used. One was to introduce another copy of the carboxysome protein CcmM gene into the cells since CcmM is essential for packing RuBisCO into the carboxysome. Another way was to tag the RuBisCO gene either on the N terminus of the large subunit or on the C terminus of the small subunit by FLAG. Even though the RuBisCO level increased, the specific RuBisCO activity did not change. Fructose-1,6-/sedoheptulose-1,7-bisphosphatase (FBP/SBPase), aldolase (FBA) and transketolase (TK) were overexpressed by introducing a second copy of corresponding gene. The engineered strains with increased levels of RuBisCO, FBP/SBPase, and FBA grew faster, had higher maximum net oxygen evolution rate and accumulated more biomass when cultivated under 100µmol photons m-2 s-1 light intensity. The strain carrying more TK showed a chlorotic phenotype but still accumulated more biomass under the same light condition. Four strains with one of the CBB cycle enzymes overexpressed were selected to investigate the effects on ethanol production. Increased ethanol production and ethanol to total biomass rate were observed in the CBB cycle engineered strains. The best strain produced almost 50% ethanol out of the total biomass.

This work shows that overexpressing selected enzymes of the CBB cycle in cyanobacteria resulted in enhanced total biomass accumulation and increased compound (exampled as ethanol) production under certain growth conditions.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 63
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1616
Keyword
Cyanobacteria, CBB cycle, growth, biomass, photosynthesis, ethanol
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-338081 (URN)978-91-513-0201-0 (ISBN)
Public defence
2018-02-23, Häggsalen, Ang/10132, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2018-02-01 Created: 2018-01-07 Last updated: 2018-03-07

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