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Results for “Synthetic Biology”

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bioRxiv2018

Designer Sinorhizobium meliloti strains and multi-functional vectors for direct inter-kingdom transfer of high G+C content DNA

Storage and manipulation of large DNA fragments is crucial for synthetic biology applications, yet DNA with high G+C content can be unstable in many host organisms. Here, we report the development of Sinorhizobium meliloti as a new universal host that can store DNA, including high G+C content, and mobilize DNA to Escherichia coli, Saccharomyces cerevisiae, and the eukaryotic microalgae Phaeodactylum tricornutum. We deleted the S. meliloti hsdR restriction-system to enable DNA transformation with up to 1.4 x 105 efficiency. Multi-host and multi-functional shuttle vectors (MHS) were constructed and shown to stably replicate in S. meliloti, E. coli, S. cerevisiae, and P. tricornutum, with a copy-number inducible E. coli origin for isolating plasmid DNA. Crucially, we demonstrated that S. meliloti can act as a universal conjugative donor for MHS plasmids with a cargo of at least 62 kb of G+C rich DNA derived from Deinococcus radiodurans.

synthetic biology↗

bioRxiv2023

Evolution is All You Need in Promoter Design and Optimization

Predicting the strength of promoters and guiding their directed evolution is a crucial task in synthetic biology. This approach significantly reduces the experimental costs in conventional promoter engineering. Previous studies employing machine learning or deep learning methods have shown some success in this task, but their outcomes were not satisfactory enough, primarily due to the neglect of evolutionary information. In this paper, we introduce the Chaos-Attention net for Promoter Evolution (CAPE) to address the limitations of existing methods. We comprehensively extract evolutionary information within promoters using chaos game representation and process the overall information with DenseNet and Transformer. Our model achieves state-of-the-art results on two kinds of distinct tasks. The incorporation of evolutionary information enhances the models accuracy, with transfer learning further extending its adaptability. Furthermore, experimental results confirm CAPEs efficacy in simulating in silico directed evolution of promoters, marking a significant advancement in predictive modeling for prokaryotic promoter strength. Our paper also presents a user-friendly website for the practical implementation of in silico directed evolution on promoters.

synthetic biology↗

bioRxiv2026

Synthetic cell-cell adhesion provides benefits of proximity without diffusion-related costs

Multicellularity provides many advantages over unicellularity, but accessing those benefits with synthetic biology approaches is challenging due to potential tradeoffs. The same diffusion limitations that exclude toxins can limit nutrient transport, and small intercellular spaces that facilitate sharing also increase local competition. To isolate when and how cell aggregation, an essential feature of multicellularity, is useful, we compared yeast strains differing only in expression of a single adhesion gene. Unexpectedly, aggregates containing thousands of cells showed no signs of diffusion limitations, growing as well as unicellular strains in both rich and toxic media, likely because reversible cell adhesion allows cells to exchange positions. Aggregating cells also grew better than unicellular strains in the limiting carbon conditions expected to increase diffusion limitations. In mixtures of different genotypes, these benefits were specific to cells expressing the adhesion protein. Together, these results suggest key design principles for engineering aggregates: reformable bonds provide a mechanism to sidestep the fitness costs of increased size, and the benefits within such groups may arise more from nutrient sharing than from diffusion limitations.

synthetic biology↗

bioRxiv2020

The SAGE genetic toolkit enables highly efficient, iterative site-specific genome engineering in bacteria

Sustainable enhancements to crop productivity and increased resilience to adverse conditions are critical for modern agriculture, and application of plant growth promoting rhizobacteria (PGPR) is a promising method to achieve these goals. However, many desirable PGPR traits are highly regulated in their native microbe, limited to certain plant rhizospheres, or insufficiently active for agricultural purposes. Synthetic biology can address these limitations, but its application is limited by availability of appropriate tools for sophisticated, high-throughput genome engineering that function in environments where selection for DNA maintenance is impractical. Here we present an orthogonal, Serine-integrase Assisted Genome Engineering (SAGE) system, which enables iterative, site-specific integration of up to 10 different DNA constructs at efficiency on par or better than replicating plasmids. SAGE does not require use of replicating plasmids to deliver recombination machinery, and employs a secondary serine-integrase to excise and recycle selection markers. Furthermore, unlike the widely utilized pBBR1 origin, DNA transformed using SAGE is stable without selection. We highlight SAGEs utility by constructing a 287-member constitutive promoter library with a [~]40,000-fold dynamic range in P. fluorescens SBW25. We show that SAGE functions robustly in diverse - and {gamma}-proteobacteria, thus providing evidence that it will be broadly useful for engineering industrial or environmental bacteria.

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bioRxiv2022

Experimental Data Connector (XDC): Integrating the Capture of Experimental Data and Metadata Using Standard Formats and Digital Repositories

Accelerating the development of synthetic biology applications requires reproducible experimental findings. Different standards and repositories exist to exchange experimental data and metadata. However, the associated software tools often do not support a uniform data capture, encoding, and exchange of information. A connection between digital repositories is required to prevent siloing and loss of information. To this end, we developed the Experimental Data Connector (XDC). It captures experimental data and related metadata by encoding it in standard formats and storing the converted data in digital repositories. Experimental data is then uploaded to Flapjack and the metadata to SynBioHub in a consistent manner linking these repositories. This produces complete connected experimental datasets that are exchangeable. The information is captured using a single template Excel Workbook, which can be integrated into existing experimental workflow automation processes. TOC Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/520467v1_ufig3.gif" ALT="Figure 3"> View larger version (50K): org.highwire.dtl.DTLVardef@1c5f886org.highwire.dtl.DTLVardef@3f2a6dorg.highwire.dtl.DTLVardef@fa6cb2org.highwire.dtl.DTLVardef@f63236_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗

bioRxiv2025

InSillyClo, a user-friendly web application to assist large-scale Golden Gate Cloning and MoClo workflows

Systems and synthetic biology developments often require the construction of many variants of a genetic circuit of interest, resulting in large-scale cloning campaigns. Golden Gate and Modular Cloning (MoClo), two powerful technologies enabling the scale-up of cloning workflows, play a central role for efficient circuit construction. These workflows include a number of dry-lab tasks, which are time-consuming and error-prone at scale. Currently, no software tool is available to handle these tasks in a dedicated, time-saving, and user-friendly manner. We present InSillyClo, an open-source web application to assist large-scale Golden Gate cloning and MoClo workflows. It supports an easy specification of genetic designs at any scale, followed by the automated generation of comprehensive workflow-related data. Moreover, InSillyClo leverages Modular Cloning with a versatile typing system of parts to generate user-defined workflows. InSillyClo is open source, accessible with or without user registration, and can also be used locally.

synthetic biology↗

bioRxiv2026

Orthogonal Acoustic Control of Gene Expression Using a Synthetic T7RNAP Rapa-Inducible Dimerization System

Precise spatiotemporal regulation of engineered microbes remains a critical bottleneck in synthetic biology. While ultrasound is extensively utilized for imaging and drug delivery, its translation into bacterial chassis is hindered by the lack of stringent biochemical triggers. Here, we present a rationally designed, ultrasound-responsive hybrid molecular switch based on a strict acoustic-biochemical "AND-gate". We engineered a highly sensitive split-T7 RNA polymerase system, which the dimerization and subsequent gene transcription can only be triggered in the presence of both ultrasound and a PEG-modified rapamycin. By systematically optimizing the acoustic parameters, we deployed this spatiotemporal switch to dynamically regulate a microbial consortium. With lysisE suicide protein as the output module, we achieved precise and programmable tuning of bacterial population in a co-culture system. This acoustic gating strategy may provide a robust and versatile toolkit for complex microbiome engineering and dynamic biomanufacturing. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=158 SRC="FIGDIR/small/733485v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@6d229corg.highwire.dtl.DTLVardef@fb5d1eorg.highwire.dtl.DTLVardef@9e905dorg.highwire.dtl.DTLVardef@17e3a1_HPS_FORMAT_FIGEXP M_FIG Graphic Abstract C_FIG

Synthetic Biology↗

bioRxiv2020

Systematic Quantification of Sequence and Structural Determinants Controlling mRNA stability in Bacterial Operons

mRNA degradation is a central process that affects all gene expression levels, and yet the determinants that control mRNA decay rates remain poorly characterized. Here, we applied a synthetic biology, learn-by-design approach to elucidate the sequence and structural determinants that control mRNA stability in bacterial operons. We designed, constructed, and characterized 82 operons, systematically varying RNAse binding site characteristics, translation initiation rates, and transcriptional terminator efficiencies in the 5 UTR, intergenic, and 3 UTR regions, and measuring their mRNA levels using RT-qPCR assays. We show that introducing long single-stranded RNA into 5 UTRs reduced mRNA levels by up to 9.4-fold and that lowering translation rates reduced mRNA levels by up to 11.8-fold. We also found that RNAse binding sites in intergenic regions had much lower effects on mRNA levels. Surprisingly, changing transcriptional termination efficiency or introducing long single-stranded RNA into 3 UTRs had no effect on upstream mRNA levels. From these measurements, we developed and validated biophysical models of ribosome protection and RNAse activity with excellent quantitative correspondence. We also formulated design rules to rationally control a mRNAs stability, facilitating the automated design of engineered genetic systems with desired functionalities.

synthetic biology↗

bioRxiv2019

Design of a transcriptional biosensor for the portable, on-demand detection of cyanuric acid

Rapid molecular biosensing is an emerging application area for synthetic biology. Here, we engineer a portable biosensor for cyanuric acid (CYA), an analyte of interest for human and environmental health, using a LysR-type transcription regulator (LTTR) from Pseudomonas within the context of Escherichia coli gene expression machinery. To overcome cross-host portability challenges of LTTRs, we rationally engineered hybrid Pseudomonas-E. coli promoters by integrating DNA elements required for transcriptional activity and ligand-dependent regulation from both hosts, which enabled E. coli to function as whole-cell biosensor for CYA. To alleviate challenges of whole-cell biosensing, we adapted these promoter designs to function within a freeze-dried E. coli cell-free system to sense CYA. This portable, on-demand system robustly detects CYA within an hour from laboratory and real-world samples and works with both fluorescent and colorimetric reporters. This work elucidates general principles to facilitate the engineering of a wider array of LTTR-based environmental sensors.

synthetic biology↗

bioRxiv2021

Stabilisation of Antithetic Control via Molecular Buffering

A key goal in synthetic biology is the construction of molecular circuits that robustly adapt to perturbations. Although many natural systems display perfect adaptation, whereby stationary molecular concentrations are insensitive to perturbations, its de novo engineering has proven elusive. The discovery of the antithetic control motif was a significant step toward a universal mechanism for engineering perfect adaptation. Antithetic control provides perfect adaptation in a wide range of systems, but it can lead to oscillatory dynamics due to loss of stability, and moreover, it can lose perfect adaptation in fast growing cultures. Here, we introduce an extended antithetic control motif that resolves these limitations. We show that molecular buffering, a widely conserved mechanism for homeostatic control in nature, stabilises oscillations and allows for near-perfect adaptation during rapid growth. We study multiple buffering topologies and compare their performance in terms of their stability and adaptation properties. We illustrate the benefits of our proposed strategy in exemplar models for biofuel production and growth rate control in bacterial cultures. Our results provide an improved circuit for robust control of biomolecular systems.

synthetic biology↗

bioRxiv2023

Design and assembly of the 117-kb Phaeodactylum tricornutum chloroplast genome

There is a growing impetus to expand the repository of chassis available to synthetic biologists. The chloroplast genome presents a unique chassis for engineering photosynthetic eukaryotes by virtue of its compact size, lack of epigenetic regulation, and containment within the secluded lipid bilayers of the organelle. The development of the chloroplast as a synthetic biology chassis, however, has been limited by a lack of efficient techniques for whole genome cloning and engineering. Here, we demonstrate two approaches for cloning the 117 kb Phaeodactylum tricornutum chloroplast genome that have 90 to 100% efficiency when screening as few as ten Saccharomyces cerevisiae colonies following yeast assembly. The first method directly uses PCR-amplified fragments of the genome for yeast assembly, whereas the second method relies upon the pre-cloning of eight overlapping genomic regions into individual plasmids that they can later be released from. The cloned genome can be stably maintained and propagated within Escherichia coli, which provides an exciting opportunity for engineering a novel delivery mechanism for bringing DNA directly to the algal chloroplast. As well, one of the cloned genomes was designed to contain a single SapI site within the yeast URA3 open-reading frame, which can be used to linearize the genome and integrate designer cassettes via golden-gate cloning or further iterations of yeast assembly.

synthetic biology↗

bioRxiv2023

A cell-free transcription-translation pipeline for recreating methylation patterns boosts DNA transformation in bacteria

The bacterial world offers diverse strains for understanding medical and environmental processes and for engineering synthetic-biology chasses. However, genetically manipulating these strains has faced a long-standing bottleneck: how to efficiently transform DNA. Here we report IMPRINT, a generalized, rapid and scalable approach based on cell-free transcription-translation (TXTL) systems to overcome DNA restriction, a prominent barrier to transformation. IMPRINT utilizes TXTL to express DNA methyltransferases from the bacterial hosts restriction-modification systems. The expressed methyltransferases then methylate DNA in vitro to match the host DNAs methylation pattern, circumventing restriction and enhancing transformation. With IMPRINT, we efficiently multiplex methylation by diverse DNA methyltransferases and enhance plasmid transformation in gram-negative and gram-positive bacteria. We also developed a high-throughput pipeline that identifies the most consequential methyltransferases, and we apply IMPRINT to facilitate a library screen for translational rules in a hard-to-transform Bifidobacterium. Overall, IMPRINT can enhance DNA transformation, enabling use of increasingly sophisticated genetic manipulation tools across the bacterial world.

synthetic biology↗

bioRxiv2018

Two new plasmid post-segregational killing mechanisms for the implementation of synthetic gene networks in E. coli

Plasmids are the workhorse of both industrial biotechnology and synthetic biology, but ensuring they remain in bacterial cells is a challenge. Antibiotic selection, commonly used in the laboratory, cannot be used to stabilise plasmids in most real-world applications, and inserting dynamical gene networks into the genome is difficult. Plasmids have evolved several mechanisms for stability, one of which, post-segregational killing (PSK), ensures that plasmid-free cells do not grow or survive. Here we demonstrate the plasmid-stabilising capabilities of the axe/txe two component system and the microcin-V system in the probiotic bacteria Escherichia coli Nissle 1917 and show they can outperform the hok/sok system commonly used in biotechnological applications. Using plasmid stability assays, automated flow cytometry analysis, mathematical models and Bayesian statistics we quantified plasmid stability in vitro. Further, we used an in vivo mouse cancer model to demonstrate plasmid stability in a real-world therapeutic setting. These new PSK systems, plus the developed Bayesian methodology, will have wide applicability in clinical and industrial biotechnology.

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bioRxiv2024

Nuclear assembly in giant unilamellar vesicles encapsulating Xenopus egg extract

The reconstitution of a cell nucleus in a lipid bilayer-enclosed synthetic cell makes great strides in bottom-up synthetic biology. In this study, we propose a method for assembling a nucleus in giant unilamellar vesicles (GUVs). To induce reconstitution of the nucleus, we utilize interphase egg extract of African clawed frogs Xenopus laevis, known as a biochemically controllable cell-free system capable of transforming an added sperm chromatin into a nucleus in vitro. We enhanced GUV formation efficiency by the inverted emulsion method through incorporating prolonged waiting time and adding chloroform into lipid-dispersed oil, facilitating subsequent nuclear assembly reactions in the GUVs.Characterization of nucleus-like structures formed in the GUVs revealed the presence of dense DNA and accumulated GFP-NLS in the structure, indicative of functional nuclear import. Immunostaining further validated the presence of nuclear pore complexes on the surfaces of these nucleus-like structures. Our approach offers a versatile platform for constructing artificial cellular systems that closely mimic eukaryotic cells. TeaserA cell nucleus is reconstituted in lipid bilayer-enclosed confinements using egg extract from African clawed frogs.

synthetic biology↗

bioRxiv2019

Design and optimization of a cell-free atrazine biosensor

Recent advances in cell-free synthetic biology have spurred the development of in vitro molecular diagnostics that serve as effective alternatives to whole-cell biosensors. However, cell-free sensors for detecting manmade organic water contaminants such as pesticides are sparse, partially because few characterized natural biological sensors can directly detect such pollutants. Here, we present a platform for the cell-free detection of one critical water contaminant, atrazine, by combining a previously characterized cyanuric acid biosensor with a reconstituted atrazine-to-cyanuric acid metabolic pathway composed of several protein-enriched bacterial extracts mixed in a one pot reaction. Our cell-free sensor detects atrazine within an hour of incubation at an activation ratio superior to previously reported whole-cell atrazine sensors. We also show that the response characteristics of the atrazine sensor can be tuned by manipulating the component ratios of the cell-free reaction mixture. Our approach of utilizing multiple metabolic steps, encoded in protein-enriched cell-free extracts, to convert a target of interest into a molecule that can be sensed by a transcription factor is modularly designed, which should enable this work to serve as an effective proof-of-concept for rapid field-deployable detection of complex organic water contaminants.

synthetic biology↗

bioRxiv2021

A linear programming-based strategy to save pipette tips in automated DNA assembly

Laboratory automation and mathematical optimisation are key to improving the efficiency of synthetic biology research. While there are algorithms optimising the construct designs and synthesis strategies for DNA assembly, the optimisation of how DNA assembly reaction mixes are prepared remains largely unexplored. Here, we focus on reducing the pipette tip consumption of a liquid-handling robot as it delivers DNA parts across a multi-well plate where several constructs are being assembled in parallel. We propose a linear programming formulation of this problem based on the capacitated vehicle routing problem, along with an algorithm which applies a linear programming solver to our formulation, hence providing a strategy to prepare a given set of DNA assembly mixes using fewer pipette tips. The algorithm performed well in randomly generated and real-life scenarios concerning several modular DNA assembly standards, proving capable of reducing the pipette tip consumption by up to 61% in large-scale cases. Combining automatic process optimisation and robotic liquid-handling, our strategy promises to greatly improve the efficiency of DNA assembly, either used alone or in combination with other algorithmic methods.

synthetic biology↗

bioRxiv2023

Cryo-EM-guided engineering of T-box-tRNA modules with enhanced selectivity and sensitivity in translational regulation

Riboswitches are non-coding RNA elements that play vital roles in regulating gene expression. Their specific ligand-dependent structural reorganization facilitates their use as templates for design of engineered RNA switches for therapeutics, nanotechnology and synthetic biology. T-box riboswitches bind tRNAs to sense aminoacylation and control gene expression via transcription attenuation or translation inhibition. Here we determine the cryo-EM structure of the wild-type Mycobacterium smegmatis ileS T-box in complex with its cognate tRNAIle. This structure shows a very flexible antisequestrator region that tolerates both 3-OH and 2,3-cyclic phosphate modification at the 3 end of tRNAIle. Elongation of one helical turn (11-base pair) in both the tRNA acceptor arm and T-box Stem III maintains T-box-tRNA complex formation and increases the selectivity for tRNA 3 end modification. Moreover, elongation of Stem III results in [~]6-fold tighter binding to tRNA, which leads to increased sensitivity of downstream translational regulation indicated by precedent translation. Our results demonstrate that cryo-EM can guide RNA engineering to design improved riboswitch modules for translational regulation, and potentially a variety of additional functions.

synthetic biology↗

bioRxiv2023

Design of a Biohybrid Materials Circuit with Binary Decoder Functionality

Synthetic biology applies concepts from electrical engineering and information processing to endow cells with computational functionality. Transferring the underlying molecular components into materials and wiring them according to topologies inspired by electronic circuit boards has yielded materials systems that perform selected computational operations. However, the limited functionality of available building blocks is restricting the implementation of advanced information-processing circuits into materials. Here, we engineer a set of protease-based biohybrid modules the bioactivity of which can either be induced or inhibited. Guided by a quantitative mathematical model and following a design-build-test-learn cycle, we wire the modules according to circuit topologies inspired by electronic signal decoders, a fundamental motif in information processing. We design a 2-input/4-output binary decoder for the detection of two small molecules in a material framework that could perform regulated outputs in form of distinct protease activities. The here demonstrated smart material system is strongly modular and could be used for biomolecular information processing for example in advanced biosensing or drug delivery applications.

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