Browsing by Author "Haseloff, Jim"

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    Artificial Symmetry-Breaking for Morphogenetic Engineering Bacterial Colonies
    (2017) Núñez Quijada, Isaac Natán; Matute Torres, Tamara Francisca; Del Valle, Ilenne D.; Kan, Anton; Choksi, Atri; Endy, Drew; Haseloff, Jim; Rudge, Timothy; Federici, Fernán
    Morphogenetic engineering is an emerging field that explores the design and implementation of self-organized patterns, morphologies, and architectures in systems composed of multiple agents such as cells and swarm robots. Synthetic biology, on the other hand, aims to develop tools and formalisms that increase reproducibility, tractability, and efficiency in the engineering of biological systems. We seek to apply synthetic biology approaches to the engineering of morphologies in multicellular systems. Here, we describe the engineering of two mechanisms, symmetry-breaking and domain-specific cell regulation, as elementary functions for the prototyping of morphogenetic instructions in bacterial colonies. The former represents an artificial patterning mechanism based on plasmid segregation while the latter plays the role of artificial cell differentiation by spatial colocalization of ubiquitous and segregated components. This separation of patterning from actuation facilitates the design-build-test-improve engineering cycle. We created computational modules for CellModeller representing these basic functions and used it to guide the design process and explore the design space in silico. We applied these tools to encode spatially structured functions such as metabolic complementation, RNAPT7 gene expression, and CRISPRi/Cas9 regulation. Finally, as a proof of concept, we used CRISPRi/Cas technology to regulate cell growth by controlling methionine synthesis. These mechanisms start from single cells enabling the study of morphogenetic principles and the engineering of novel population scale structures from the bottom up.
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    Constructing Cell-Free Expression Systems for Low-Cost Access
    (2022) Guzman-Chavez, Fernando; Arce, Anibal; Adhikari, Abhinav; Vadhin, Sandra; Antonio Pedroza-Garcia, Jose; Gandini, Chiara; Ajioka, Jim W.; Molloy, Jenny; Sanchez-Nieto, Sobeida; Varner, Jeffrey D.; Federici, Fernan; Haseloff, Jim
    Cell-free systems for gene expression have gained attention as platforms for the facile study of genetic circuits and as highly effective tools for teaching. Despite recent progress, the technology remains inaccessible for many in low- and middle-income countries due to the expensive reagents required for its manufacturing, as well as specialized equipment required for distribution and storage. To address these challenges, we deconstructed processes required for cell-free mixture preparation and developed a set of alternative low-cost strategies for easy production and sharing of extracts. First, we explored the stability of cell-free reactions dried through a low-cost device based on silica beads, as an alternative to commercial automated freeze dryers. Second, we report the positive effect of lactose as an additive for increasing protein synthesis in maltodextrin-based cell-free reactions using either circular or linear DNA templates. The modifications were used to produce active amounts of two high-value reagents: the isothermal polymerase Bst and the restriction enzyme BsaI. Third, we demonstrated the endogenous regeneration of nucleoside triphosphates and synthesis of pyruvate in cell-free systems (CFSs) based on phosphoenol pyruvate (PEP) and maltodextrin (MDX). We exploited this novel finding to demonstrate the use of a cell-free mixture completely free of any exogenous nucleotide triphosphates (NTPs) to generate high yields of sfGFP expression. Together, these modifications can produce desiccated extracts that are 203-424-fold cheaper than commercial versions. These improvements will facilitate wider use of CFS for research and education purposes.
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    Decentralizing Cell-Free RNA Sensing With the Use of Low-Cost Cell Extracts
    (2021) Arce, Anibal; Guzman Chavez, Fernando; Gandini, Chiara; Puig, Juan; Matute, Tamara; Haseloff, Jim; Dalchau, Neil; Molloy, Jenny; Pardee, Keith; Federici, Fernan
    Cell-free gene expression systems have emerged as a promising platform for field-deployed biosensing and diagnostics. When combined with programmable toehold switch-based RNA sensors, these systems can be used to detect arbitrary RNAs and freeze-dried for room temperature transport to the point-of-need. These sensors, however, have been mainly implemented using reconstituted PURE cell-free protein expression systems that are difficult to source in the Global South due to their high commercial cost and cold-chain shipping requirements. Based on preliminary demonstrations of toehold sensors working on lysates, we describe the fast prototyping of RNA toehold switch-based sensors that can be produced locally and reduce the cost of sensors by two orders of magnitude. We demonstrate that these in-house cell lysates provide sensor performance comparable to commercial PURE cell-free systems. We further optimize these lysates with a CRISPRi strategy to enhance the stability of linear DNAs by knocking-down genes responsible for linear DNA degradation. This enables the direct use of PCR products for fast screening of new designs. As a proof-of-concept, we develop novel toehold sensors for the plant pathogen Potato Virus Y (PVY), which dramatically reduces the yield of this important staple crop. The local implementation of low-cost cell-free toehold sensors could enable biosensing capacity at the regional level and lead to more decentralized models for global surveillance of infectious disease.
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    Intercellular adhesion promotes clonal mixing in growing bacterial populations
    (2018) Kan, Anton; Del Valle, Ilenne; Rudge, Timothy; Federici, Fernán; Haseloff, Jim
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    Loop assembly: a simple and open system for recursive fabrication of DNA circuit
    (2019) Pollak, Bernardo; Cerda, Ariel; Delmans, Mihails; Álamos, Simón; Moyano, Tomás; West, Anthony; Gutiérrez, Rodrigo A.; Patron, Nicola J.; Federici, Fernán; Haseloff, Jim
    High-efficiency methods for DNA assembly have enabled the routine assembly of syntheticDNAs of increased size and complexity. However, these techniques require customization,elaborate vector sets or serial manipulations for the different stages of assembly. We have developed Loop assembly based on a recursive approach to DNA fabrication. Thesystem makes use of two Type IIS restriction endonucleases and corresponding vector sets forefficient and parallel assembly of large DNA circuits. Standardized level 0 parts can be assem-bled into circuits containing 1, 4, 16 or more genes by looping between the two vector sets.The vectors also contain modular sites for hybrid assembly using sequence overlap methods. Loop assembly enables efficient and versatile DNA fabrication for plant transformation. Weshow the construction of plasmids up to 16 genes and 38 kb with high efficiency (> 80%).We have characterized Loop assembly on over 200 different DNA constructs and validatedthe fidelity of the method by high-throughput Illumina plasmid sequencing. Our method provides a simple generalized solution for DNA construction with standardizedparts. The cloning system is provided under an OpenMTA license for unrestricted sharing andopen access.