TitleEngineering prokaryotic transcriptional activators as metabolite biosensors in yeast io-based production of chemicals and fuels is an attractive avenue to reduce dependence on petroleum. For bio-based production, biocatalysts must often be genetically modified to increase production. However, the current efficiency of genomeengineering methods and parts prospecting allows for unprecedented genotype diversity that vastly outstrips our ability to screen for best cell performance 1,2 .To meet current demand, bioengineers have started to develop genetically encoded devices and systems that enable screening and selection of better-performing biocatalysts in higher throughput. Genetic devices including oscillators, amplifiers and recorders, which have been developed based on fine-tuned relationships between input and output signals, are promising tools for programming and controlling gene expression in living cells [3][4][5] . These devices sense extracellular or intracellular perturbations and actuate cellular decision-making processes akin to logic gates in electrical circuits. Hence, from a diverse set of inputs, molecular gating components such as RNA aptamers and allosterically regulated transcription factors have been engineered to control outputs for applications such as high-throughput screening, actuation on cellular metabolism and evolution-based selection of optimal cell performance [6][7][8] .A key component in many of the reported devices is a ligandinducible transcriptional regulator. Transcriptional regulators are straightforward and powerful components, with many uses in genetic designs. Owing to their modular structure, transcriptional regulators have proven to be versatile platforms for genetically encoded Boolean logic functions 9,10 . In particular, gene switches based on ligand-binding transcriptional repressors bind to genomic targets in the absence of their cognate ligand and thereby repress gene expression of the downstream gene(s), whereas binding between ligand and repressor causes the release of the repressor from the DNA and thereby a derepression 11 . In such 'NOT' gates, simple steric hindrance of RNA polymerase progression, as in the case of the tetracycline-responsive gene switch TetR, have for decades been used for conditional control of gene expression in both prokaryotic and eukaryotic chassis 12,13 . Transcriptional repressors and other artificial transcriptional regulators can be further engineered, for example, via the addition of nuclear localization signals, destabilization domains and transcriptional activation regions, to repurpose conditional repressors into activators [13][14][15] . Though conceptually intriguing and practically relevant, the repurposing of logic gates can suffer from the inherent need for extensive engineering 9,16,17 .Though most ligand-inducible genetic devices adopted for eukaryotes historically have been founded on transcriptional repressors, a hitherto untapped resource for use in genetic designs is ligand-inducible transcriptional activators. Bac...

Observing cellular responses to perturbations is central to generating and testing hypotheses in biology. We developed a massively parallel microchemostat array capable of growing and observing 1,152 yeast-GFP strains on the single-cell level with 20 min time resolution. We measured protein abundance and localization changes in 4,085 GFP-tagged strains in response to methyl methanesulfonate and analyzed 576 GFP strains in five additional conditions for a total of more than 10,000 unique experiments, providing a systematic view of the yeast proteome in flux. We observed that processing bodies formed rapidly and synchronously in response to UV irradiation, and in conjunction with 506 deletion-GFP strains, identified four gene disruptions leading to abnormal ribonucleotide-diphosphate reductase (Rnr4) localization. Our microchemostat platform enables the large-scale interrogation of proteomes in flux and permits the concurrent observation of protein abundance, localization, cell size, and growth parameters on the single-cell level for thousands of microbial cultures in one experiment.O bserving proteins in the cellular milieu has been a longstanding technical challenge in biology. One major advance was the development of GFP, enabling the visualization of proteins in vivo (1). High-content imaging has been primarily applied to mammalian cells, using either reverse transfection arrays or microtiter-based systems in which the slow doubling time of mammalian cells enables long-term imaging under static conditions (2, 3).The Saccharomyces cerevisiae GFP fusion library covering 4,159 proteins provided the first static view of global protein abundance, localization, and noise (4, 5). This library was recently used to establish the static differences in protein abundance and localization in response to DNA replication stress induced by methyl methanesulfonate (MMS) and hydroxyurea (HU) (6), in response to DTT, H 2 O 2 , and nitrogen starvation (7), and 800 cytoplasmic proteins were analyzed upon entry into stationary phase (8). These three recent large-scale screens all relied on standard microtiter plates for imaging the yeast strains at a single time point before and after perturbation. Meanwhile, microfluidic devices emerged as powerful tools for conducting complex time-lapse experiments on small to medium scales (9, 10), enabling the analysis of cellular network responses (11) and the implementation of synthetically engineered systems (12). However, it has thus far been technically impossible to interrogate thousands of continuously growing microbial strains with high spatiotemporal resolution in a single experiment.Despite the fact that a wealth of systems-level information is available for S. cerevisiae, the single-cell temporal dynamics of protein abundance and localization has not yet been measured on a systems scale. To enable such analyses we developed a microfluidic platform capable of growing and observing 1,152 yeast strains with a temporal resolution of 20 min. We explored the dynamic behavior of ∼2/3 of the...

Homologous recombination (HR) in Saccharomyces cerevisiae has been harnessed for both plasmid construction and chromosomal integration of foreign DNA. Still, native HR machinery is not efficient enough for complex and marker-free genome engineering required for modern metabolic engineering. Here, we present a method for marker-free multiloci integration of in vivo assembled DNA parts. By the use of CRISPR/Cas9-mediated one-step double-strand breaks at single, double and triple integration sites we report the successful in vivo assembly and chromosomal integration of DNA parts. We call our method CasEMBLR and validate its applicability for genome engineering and cell factory development in two ways: (i) introduction of the carotenoid pathway from 15 DNA parts into three targeted loci, and (ii) creation of a tyrosine production strain using ten parts into two loci, simultaneously knocking out two genes. This method complements and improves the current set of tools available for genome engineering in S. cerevisiae.