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Douglas Densmore

Bio: Douglas Densmore is an academic researcher from Boston University. The author has contributed to research in topics: Synthetic biology & Electronic design automation. The author has an hindex of 28, co-authored 103 publications receiving 3363 citations. Previous affiliations of Douglas Densmore include Xilinx & Lawrence Berkeley National Laboratory.


Papers
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Journal ArticleDOI
01 Apr 2016-Science
TL;DR: Electronic design automation principles from EDA are applied to enable increased circuit complexity and to simplify the incorporation of synthetic gene regulation into genetic engineering projects, and it is demonstrated that engineering principles can be applied to identify and suppress errors that complicate the compositions of larger systems.
Abstract: INTRODUCTION Cells respond to their environment, make decisions, build structures, and coordinate tasks. Underlying these processes are computational operations performed by networks of regulatory proteins that integrate signals and control the timing of gene expression. Harnessing this capability is critical for biotechnology projects that require decision-making, control, sensing, or spatial organization. It has been shown that cells can be programmed using synthetic genetic circuits composed of regulators organized to generate a desired operation. However, the construction of even simple circuits is time-intensive and unreliable. RATIONALE Electronic design automation (EDA) was developed to aid engineers in the design of semiconductor-based electronics. In an effort to accelerate genetic circuit design, we applied principles from EDA to enable increased circuit complexity and to simplify the incorporation of synthetic gene regulation into genetic engineering projects. We used the hardware description language Verilog to enable a user to describe a circuit function. The user also specifies the sensors, actuators, and “user constraints file” (UCF), which defines the organism, gate technology, and valid operating conditions. Cello (www.cellocad.org) uses this information to automatically design a DNA sequence encoding the desired circuit. This is done via a set of algorithms that parse the Verilog text, create the circuit diagram, assign gates, balance constraints to build the DNA, and simulate performance. RESULTS Cello designs circuits by drawing upon a library of Boolean logic gates. Here, the gate technology consists of NOT/NOR logic based on repressors. Gate connection is simplified by defining the input and output signals as RNA polymerase (RNAP) fluxes. We found that the gates need to be insulated from their genetic context to function reliably in the context of different circuits. Each gate is isolated using strong terminators to block RNAP leakage, and input interchangeability is improved using ribozymes and promoter spacers. These parts are varied for each gate to avoid breakage due to recombination. Measuring the load of each gate and incorporating this into the optimization algorithms further reduces evolutionary pressure. Cello was applied to the design of 60 circuits for Escherichia coli , where the circuit function was specified using Verilog code and transformed to a DNA sequence. The DNA sequences were built as specified with no additional tuning, requiring 880,000 base pairs of DNA assembly. Of these, 45 circuits performed correctly in every output state (up to 10 regulators and 55 parts). Across all circuits, 92% of the 412 output states functioned as predicted. CONCLUSION Our work constitutes a hardware description language for programming living cells. This required the co-development of design algorithms with gates that are sufficiently simple and robust to be connected by automated algorithms. We demonstrate that engineering principles can be applied to identify and suppress errors that complicate the compositions of larger systems. This approach leads to highly repetitive and modular genetics, in stark contrast to the encoding of natural regulatory networks. The use of a hardware-independent language and the creation of additional UCFs will allow a single design to be transformed into DNA for different organisms, genetic endpoints, operating conditions, and gate technologies.

813 citations

Journal ArticleDOI
TL;DR: This work exploits the modularity of a refactored Klebsiella oxytoca nitrogen fixation (nif) gene cluster to build genetic permutations that could not be achieved by starting from the wild-type cluster to provide a useful, fast tool for genetic optimization and hypothesis testing.
Abstract: Combinatorial replacement and rearrangement of genetic parts in a refactored nitrogen fixation gene cluster lead to improved performance.

315 citations

Journal ArticleDOI
TL;DR: The Synthetic Biology Open Language (SBOL) is described, a proposed data standard for exchanging designs within the synthetic biology community that represents synthetic biology designs in a community-driven, formalized format for exchange between software tools, research groups and commercial service providers.
Abstract: The synthetic biology research community describes a standard language for exchanging designs of biological 'parts'. The re-use of previously validated designs is critical to the evolution of synthetic biology from a research discipline to an engineering practice. Here we describe the Synthetic Biology Open Language (SBOL), a proposed data standard for exchanging designs within the synthetic biology community. SBOL represents synthetic biology designs in a community-driven, formalized format for exchange between software tools, research groups and commercial service providers. The SBOL Developers Group has implemented SBOL as an XML/RDF serialization and provides software libraries and specification documentation to help developers implement SBOL in their own software. We describe early successes, including a demonstration of the utility of SBOL for information exchange between several different software tools and repositories from both academic and industrial partners. As a community-driven standard, SBOL will be updated as synthetic biology evolves to provide specific capabilities for different aspects of the synthetic biology workflow.

250 citations

Journal ArticleDOI
TL;DR: A taxonomy for ESL tools and methodologies is presented that combines UC Berkeley's platform-based design terminologies with Dan Gajski's Y-chart work to help stem the tide of confusion in the ESL world.
Abstract: This article presents a taxonomy for ESL tools and methodologies that combines UC Berkeley's platform-based design terminologies with Dan Gajski's Y-chart work. This is timely and necessary because in the ESL world we seem to be building tools without first establishing an appropriate design flow or methodology, thereby creating a lot of confusion. This taxonomy can help stem the tide of confusion

173 citations

Journal ArticleDOI
TL;DR: This work has developed a publicly available collection of modular DNA parts and enhanced MoClo protocols to enable rapid one-pot, multipart assembly, combinatorial design, and expression tuning in Escherichia coli.
Abstract: Multipart and modular DNA part libraries and assembly standards have become common tools in synthetic biology since the publication of the Gibson and Golden Gate assembly methods, yet no multipart modular library exists for use in bacterial systems. Building upon the existing MoClo assembly framework, we have developed a publicly available collection of modular DNA parts and enhanced MoClo protocols to enable rapid one-pot, multipart assembly, combinatorial design, and expression tuning in Escherichia coli. The Cross-disciplinary Integration of Design Automation Research lab (CIDAR) MoClo Library is openly available and contains promoters, ribosomal binding sites, coding sequence, terminators, vectors, and a set of fluorescent control plasmids. Optimized protocols reduce reaction time and cost by >80% from that of previously published protocols.

148 citations


Cited by
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01 Jan 2010
TL;DR: It is found that women over 50 are more likely to have a family history of diabetes, especially if they are obese, than women under the age of 50.
Abstract: Hypertension 66 (20.3%) 24 (24.2%) 30 (16.3%) NS Diabetes 20 (6.2%) 7 (7.1%) 10 (5.4%) NS Excess weight 78 (24%) 27 (27.3%) 44 (23.9%) NS Smokers 64 (19.7%) 17 (17.2%) 35 (19.0%) NS Age >50 years 137 (42.2%) 54 (54.5%) 67 (36.4%) <0.02 Kidney disease 7 (2.2%) 1 (1%) 5 (2.7%) NS Family history, DM 102 (31.4%) 28 (28.3%) 66 (35.9%) NS

1,369 citations

Journal ArticleDOI
25 Mar 2016-Science
TL;DR: This work set out to define a minimal cellular genome experimentally by designing and building one, then testing it for viability, and applied whole-genome design and synthesis to the problem of minimizing a cellular genome.
Abstract: We used whole-genome design and complete chemical synthesis to minimize the 1079-kilobase pair synthetic genome of Mycoplasma mycoides JCVI-syn1.0. An initial design, based on collective knowledge of molecular biology combined with limited transposon mutagenesis data, failed to produce a viable cell. Improved transposon mutagenesis methods revealed a class of quasi-essential genes that are needed for robust growth, explaining the failure of our initial design. Three cycles of design, synthesis, and testing, with retention of quasi-essential genes, produced JCVI-syn3.0 (531 kilobase pairs, 473 genes), which has a genome smaller than that of any autonomously replicating cell found in nature. JCVI-syn3.0 retains almost all genes involved in the synthesis and processing of macromolecules. Unexpectedly, it also contains 149 genes with unknown biological functions. JCVI-syn3.0 is a versatile platform for investigating the core functions of life and for exploring whole-genome design.

1,047 citations

Journal ArticleDOI
10 Mar 2016-Cell
TL;DR: How new technologies can enable metabolic engineering to be scaled up to the industrial level, either by cutting off the lines of control for endogenous metabolism or by infiltrating the system with disruptive, heterologous pathways that overcome cellular regulation is discussed.

891 citations