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Identification of aromatic-inducible promoters and heterologous biosensors as tuning elements for styrene production in E. coli

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One of the primary bottlenecks to chemical production in biological organisms is the toxicity of the chemical. Overexpression of efflux pumps has been shown to increase tolerance to aromatic compounds such as styrene and styrene oxide. Tight control of pum

One of the primary bottlenecks to chemical production in biological organisms is the toxicity of the chemical. Overexpression of efflux pumps has been shown to increase tolerance to aromatic compounds such as styrene and styrene oxide. Tight control of pump expression is necessary to maximize titers and prevent excessive strain on the cells. This study aimed to identify aromatic-sensitive native promoters and heterologous biosensors for construction of closed-loop control of efflux pump expression in E. coli. Using a promoter library constructed by Zaslaver et al., activation was measured through GFP output. Promoters were evaluated for their sensitivity to the addition of one of four aromatic compounds, their "leaking" of signal, and their induction threshold. Out of 43 targeted promoters, 4 promoters (cmr, mdtG, yahN, yajR) for styrene oxide, 2 promoters (mdtG, yahN) for styrene, 0 promoters for 2-phenylethanol, and 1 promoter for phenol (pheP) were identified as ideal control elements in aromatic bioproduction. In addition, a series of three biosensors (NahR, XylS, DmpR) known to be inducible by other aromatics were screened against styrene oxide, 2-phenylethanol, and phenol. The targeted application of these biosensors is aromatic-induced activation of linked efflux pumps. All three biosensors responded strongly in the presence of styrene oxide and 2-phenylethanol, with minor activation in the presence of phenol. Bioproduction of aromatics continues to gain traction in the biotechnology industry, and the continued discovery of aromatic-inducible elements will be essential to effective pathway control.

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2018-05

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Using Natural Diversity of Quorum Sensing to Expand the Synthetic Biology Toolbox

Description

Currently in synthetic biology only the Las, Lux, and Rhl quorum sensing pathways have been adapted for broad engineering use. Quorum sensing allows a means of cell to cell communication in which a designated sender cell produces quorum sensing molecules

Currently in synthetic biology only the Las, Lux, and Rhl quorum sensing pathways have been adapted for broad engineering use. Quorum sensing allows a means of cell to cell communication in which a designated sender cell produces quorum sensing molecules that modify gene expression of a designated receiver cell. While useful, these three quorum sensing pathways exhibit a nontrivial level of crosstalk, hindering robust engineering and leading to unexpected effects in a given design. To address the lack of orthogonality among these three quorum sensing pathways, previous scientists have attempted to perform directed evolution on components of the quorum sensing pathway. While a powerful tool, directed evolution is limited by the subspace that is defined by the protein. For this reason, we take an evolutionary biology approach to identify new orthogonal quorum sensing networks and test these networks for cross-talk with currently-used networks. By charting characteristics of acyl homoserine lactone (AHL) molecules used across quorum sensing pathways in nature, we have identified favorable candidate pathways likely to display orthogonality. These include Aub, Bja, Bra, Cer, Esa, Las, Lux, Rhl, Rpa, and Sin, which we have begun constructing and testing. Our synthetic circuits express GFP in response to a quorum sensing molecule, allowing quantitative measurement of orthogonality between pairs. By determining orthogonal quorum sensing pairs, we hope to identify and adapt novel quorum sensing pathways for robust use in higher-order genetic circuits.

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2015-05

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Development of a Polyethylene terephthalate Hydrolase Expression System in Escherichia coli

Description

The increased shift towards environmentalism has brought notable attention to a universal excessive plastic consumption and subsequent plastic overload in landfills. Among these plastics, polyethylene terephthalate, more commonly known as PET, constitutes a large percentage of the waste that ends

The increased shift towards environmentalism has brought notable attention to a universal excessive plastic consumption and subsequent plastic overload in landfills. Among these plastics, polyethylene terephthalate, more commonly known as PET, constitutes a large percentage of the waste that ends up in landfills. Material and chemical/thermal methods for recycling are both costly, and inefficient, which necessitates a more sustainable and cheaper alternative. The current study aims at fulfilling that role through genetic engineering of Bacillus subtilis with integration of genes from LCC, Ideonella sakaiensis, and Bacillus subtilis. The plasmid construction was done through restriction cloning. A recombinant plasmid for the expression of LCC was constructed, and transformed into Escherichia coli. Future experiments for this study should include redesigning of primers, with possible combination of signal peptides with genes during construct design, and more advanced assays for effective outcomes.

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2021-05

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Developing engineered polymerases for practical applications in synthetic biology

Description

Advances in chemical synthesis have enabled new lines of research with unnatural genetic polymers whose modified bases or sugar-phosphate backbones have potential therapeutic and biotechnological applications. Maximizing the potential of these synthetic genetic systems requires inventing new molecular biology tools

Advances in chemical synthesis have enabled new lines of research with unnatural genetic polymers whose modified bases or sugar-phosphate backbones have potential therapeutic and biotechnological applications. Maximizing the potential of these synthetic genetic systems requires inventing new molecular biology tools that can both generate and faithfully replicate unnatural polymers of significant length. Threose nucleic acid (TNA) has received significant attention as a complete replication system has been developed by engineering natural polymerases to broaden their substrate specificity. The system, however, suffers from a high mutational load reducing its utility. This thesis will cover the development of two new polymerases capable of transcribing and reverse transcribing TNA polymers with high efficiency and fidelity. The polymerases are identified using a new strategy wherein gain-of-function mutations are sampled in homologous protein architectures leading to subtle optimization of protein function. The new replication system has a fidelity that supports the propagation of genetic information enabling in vitro selection of functional TNA molecules. TNA aptamers to human alpha-thrombin are identified and demonstrated to have superior stability compared to DNA and RNA in biologically relevant conditions. This is the first demonstration that functional TNA molecules have potential in biotechnology and molecular medicine.

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Date Created
2015

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The synthetic biology of a man-made protein

Description

Synthetic biology is constantly evolving as new ideas are incorporated into this increasingly flexible field. It incorporates the engineering of life with standard genetic parts and methods; new organisms with new genomes; expansion of life to include new components, capabilities,

Synthetic biology is constantly evolving as new ideas are incorporated into this increasingly flexible field. It incorporates the engineering of life with standard genetic parts and methods; new organisms with new genomes; expansion of life to include new components, capabilities, and chemistries; and even completely synthetic organisms that mimic life while being composed of non-living matter. We have introduced a new paradigm of synthetic biology that melds the methods of in vitro evolution with the goals and philosophy of synthetic biology. The Family B proteins represent the first de novo evolved natively folded proteins to be developed with increasingly powerful tools of molecular evolution. These proteins are folded and functional, composed of the 20 canonical amino acids, and in many ways resemble natural proteins. However, their evolutionary history is quite different from natural proteins, as it did not involve a cellular environment. In this study, we examine the properties of DX, one of the Family B proteins that have been evolutionarily optimized for folding stability. Described in chapter 2 is an investigation into the primitive catalytic properties of DX, which seems to have evolved a serendipitous ATPase activity in addition to its selected ATP binding activity. In chapters 3 and 4 we express the DX gene in E. coli cells and observe massive changes in cell morphology, biochemistry, and life cycle. Exposure to DX activates several defense systems in E. coli, including filamentation, cytoplasmic segregation, and reversion to a viable but non-culturable state. We examined these phenotypes in detail and present a model that accounts for how DX causes such a rearrangement of the cell.

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Date Created
2011

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Engineering a Co-Culture of Bacteria and Yeast for the Production of Renewable p-Coumaric Acid

Description

p-Coumaric acid is used in the food, pharmaceutical, and cosmetic industries due to its versatile properties. While prevalent in nature, harvesting the compound from natural sources is inefficient, requiring large quantities of producing crops and numerous extraction and purification steps.

p-Coumaric acid is used in the food, pharmaceutical, and cosmetic industries due to its versatile properties. While prevalent in nature, harvesting the compound from natural sources is inefficient, requiring large quantities of producing crops and numerous extraction and purification steps. Thus, the large-scale production of the compound is both difficult and costly. This research aims to produce p-coumarate directly from renewable and sustainable glucose using a co-culture of Yeast and E. Coli. Methods used in this study include: designing optimal media for mixed-species microbial growth, genetically engineering both strains to build the production pathway with maximum yield, and analyzing the presence of p-Coumarate and its pathway intermediates using High Performance Liquid Chromatography (HPLC). To date, the results of this project include successful integration of C4H activity into the yeast strain BY4741 ∆FDC1, yielding a strain that completely consumed trans-cinnamate (initial concentration of 50 mg/L) and produced ~56 mg/L p-coumarate, a resting cell assay of the co-culture that produced 0.23 mM p-coumarate from an initial L-Phenylalanine concentration of 1.14 mM, and toxicity tests that confirmed the toxicity of trans-cinnamate to yeast for concentrations above ~50 mg/L. The hope for this project is to create a feasible method for producing p-Coumarate sustainably.

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Date Created
2016-12

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Development of an artificial genetic system capable of Darwinian evolution

Description

The principle of Darwinian evolution has been applied in the laboratory to nucleic acid molecules since 1990, and led to the emergence of in vitro evolution technique. The methodology of in vitro evolution surveys a large number of different molecules

The principle of Darwinian evolution has been applied in the laboratory to nucleic acid molecules since 1990, and led to the emergence of in vitro evolution technique. The methodology of in vitro evolution surveys a large number of different molecules simultaneously for a pre-defined chemical property, and enrich for molecules with the particular property. DNA and RNA sequences with versatile functions have been identified by in vitro selection experiments, but many basic questions remain to be answered about how these molecules achieve their functions. This dissertation first focuses on addressing a fundamental question regarding the molecular recognition properties of in vitro selected DNA sequences, namely whether negatively charged DNA sequences can be evolved to bind alkaline proteins with high specificity. We showed that DNA binders could be made, through carefully designed stringent in vitro selection, to discriminate different alkaline proteins. The focus of this dissertation is then shifted to in vitro evolution of an artificial genetic polymer called threose nucleic acid (TNA). TNA has been considered a potential RNA progenitor during early evolution of life on Earth. However, further experimental evidence to support TNA as a primordial genetic material is lacking. In this dissertation we demonstrated the capacity of TNA to form stable tertiary structure with specific ligand binding property, which suggests a possible role of TNA as a pre-RNA genetic polymer. Additionally, we discussed the challenges in in vitro evolution for TNA enzymes and developed the necessary methodology for future TNA enzyme evolution.

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Date Created
2013

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Dilly Final Project (Spring 2022)

Description

Industries and research utilizing genetically-engineered organisms are often subject to strict containment requirements such as physical isolation or specialized equipment to prevent an unintended escape. A relatively new field of research looks for ways to engineer intrinsic containment techniques- genetic

Industries and research utilizing genetically-engineered organisms are often subject to strict containment requirements such as physical isolation or specialized equipment to prevent an unintended escape. A relatively new field of research looks for ways to engineer intrinsic containment techniques- genetic safeguards that prevent an organism from surviving outside of specific conditions. As interest in this field has grown over the last few decades, researchers in molecular and synthetic biology have discovered many novel ways to accomplish this containment, but the current literature faces some ambiguity and overlap in the ways they describe various biocontainment methods. Additionally, the way publications report the robustness of the techniques they test is inconsistent, making it uncertain how regulators could assess the safety and efficacy of these methods if they are eventually to be used in practical, consumer applications. This project organizes and clarifies the descriptions of these techniques within an interactive flowchart, linking to definitions and references to publications on each within an Excel table. For each reference, variables such as the containment approach, testing methods, and results reported are compiled, to illustrate the varying degrees to which these techniques are tested.

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Date Created
2022-05

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Containment Flowchart With Links

Description

Industries and research utilizing genetically-engineered organisms are often subject to strict containment requirements such as physical isolation or specialized equipment to prevent an unintended escape. A relatively new field of research looks for ways to engineer intrinsic containment techniques- genetic

Industries and research utilizing genetically-engineered organisms are often subject to strict containment requirements such as physical isolation or specialized equipment to prevent an unintended escape. A relatively new field of research looks for ways to engineer intrinsic containment techniques- genetic safeguards that prevent an organism from surviving outside of specific conditions. As interest in this field has grown over the last few decades, researchers in molecular and synthetic biology have discovered many novel ways to accomplish this containment, but the current literature faces some ambiguity and overlap in the ways they describe various biocontainment methods. Additionally, the way publications report the robustness of the techniques they test is inconsistent, making it uncertain how regulators could assess the safety and efficacy of these methods if they are eventually to be used in practical, consumer applications. This project organizes and clarifies the descriptions of these techniques within an interactive flowchart, linking to definitions and references to publications on each within an Excel table. For each reference, variables such as the containment approach, testing methods, and results reported are compiled, to illustrate the varying degrees to which these techniques are tested.

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Date Created
2022-05

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Literature Review and Definitions

Description

Industries and research utilizing genetically-engineered organisms are often subject to strict containment requirements such as physical isolation or specialized equipment to prevent an unintended escape. A relatively new field of research looks for ways to engineer intrinsic containment techniques- genetic

Industries and research utilizing genetically-engineered organisms are often subject to strict containment requirements such as physical isolation or specialized equipment to prevent an unintended escape. A relatively new field of research looks for ways to engineer intrinsic containment techniques- genetic safeguards that prevent an organism from surviving outside of specific conditions. As interest in this field has grown over the last few decades, researchers in molecular and synthetic biology have discovered many novel ways to accomplish this containment, but the current literature faces some ambiguity and overlap in the ways they describe various biocontainment methods. Additionally, the way publications report the robustness of the techniques they test is inconsistent, making it uncertain how regulators could assess the safety and efficacy of these methods if they are eventually to be used in practical, consumer applications. This project organizes and clarifies the descriptions of these techniques within an interactive flowchart, linking to definitions and references to publications on each within an Excel table. For each reference, variables such as the containment approach, testing methods, and results reported are compiled, to illustrate the varying degrees to which these techniques are tested.

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Agent

Created

Date Created
2022-05