Judicial Selection - What is Right for Mississippi

Symposium - The Judicial Selectio

Functional screening and in vitro analysis reveals thioesterases with enhanced substrate specificity profiles that improve short-chain fatty acid production in Escherichia coli

Short-chain fatty acid (SCFAs) biosynthesis is pertinent to production of biofuels, industrial compounds, and pharmaceuticals from renewable resources. To expand on Escherichia coli SCFA products, we previously implemented a coenzyme A (CoA)-dependent pathway that condenses acetyl-CoA to a diverse group of short chain fatty acyl-CoAs. To increase product titers and reduce premature pathway termination products, we describe in vivo and in vitro analyses to understand and improve the specificity of the acyl-CoA thioestera enzyme, which releases fatty acids from CoA. A total of 62 putative bacterial thioesterases, including from the cow rumen microbiome, were inserted into a pathway that condenses acetyl-CoA to an acyl-CoAmolecule derived from exogenously provided propionic or isobutyric acid. Functional screening revealed thioesterases that increase production of saturated (valerate), unsaturated (trans-2-pentenoate) and branched (4-methylvalerate) SCFAs compared to overexpression of E. coli thioesterase tesB or native expression of endogenous thioesterases. To determine if altered thioesterase acyl-CoA substrate specificity caused the increase in product titers, six of the most promising enzymes were analyzed in vitro. Biochemical assays revealed that the most productive thioesterases rely on promiscuous activity, but have greater specificity for product-associated acyl-CoAs than for precursor acyl-CoAs. Here we introduce novel thioesterases with improved specificity for saturated, branched and unsaturated short-chain acyl-CoAs, thereby expanding the diversity of potential fatty acid products while increasing titers of current products. The growing uncertainty associated with protein database annotations denotes this study as a model for isolating functional biochemical pathway enzymes in situations where experimental evidence of enzyme function is absent.United States. Army Research Office (Institute for Collaborative Biotechnologies, grant W911NF-09-0001

Metabolic Engineering

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Cantua dendritica (Polemoniaceae), a New Species from Peru, and Two New Cantua Names

Cantua dendritica is described as new. This species is apparently restricted to the region around Paucartambo, Department of Cusco, Peru. Related to, and frequently identified as, Cantua flexuosa, this new species differs in its glandular calyx, highly branched trichomes on the margin of the corolla lobes, and its softly herbaceous, glandular pilose leaves. In addition, two new names are proposed in Cantua for the two species of Huthia that have been transferred to Cantua, C. volcanica (formerly Huthia caerulea), and C. mediamnis (formerly H. longiflora)

The zero-sum game of pathway optimization: Emerging paradigms for tuning gene expression

With increasing price volatility and growing awareness of the lack of sustainability of traditional chemical synthesis, microbial chemical production has been tapped as a promising renewable alternative for the generation of diverse, stereospecific compounds. Nonetheless, many attempts to generate them are not yet economically viable. Due to the zero-sum nature of microbial resources, traditional strategies of pathway optimization are attaining minimal returns. This result is in part a consequence of the gross changes in host physiology resulting from such efforts and underscores the need for more precise and subtle forms of gene modulation. In this review, we describe alternative strategies and emerging paradigms to address this problem and highlight potential solutions from the emerging field of synthetic biology.National Science Foundation (U.S.) (Synthetic Biology Engineering Research Center (SynBERC), grant number EEC-0540879)National Science Foundation (U.S.) (NSF CAREER Award (grant number CBET-0954986))Natural Sciences and Engineering Research Council of Canada (Fellowship

Window Dressing, Data Mining, Or Data Errors: A Re-Examination Of The Dogs Of The Dow Theory

We re-examine the Dow dividend yield anomaly to ascertain if data errors create the superior returns of the trading rule.  Empirical testing, using both parametric and nonparametric methods, suggests that the trading rule outperforms the index.  Additionally, data errors are not the drivers of superior trading rule returns.  Moreover, the Chow breakpoint test of structural stability suggests that neither window dressing nor data mining explain this phenomenon.  Finally, a turn of the year formation date fails to explain superior trading rule returns, further mitigating the data mining explanation

Microbial Engineering for Aldehyde Synthesis

Aldehydes are a class of chemicals with many industrial uses. Several aldehydes are responsible for flavors and fragrances present in plants, but aldehydes are not known to accumulate in most natural microorganisms. In many cases, microbial production of aldehydes presents an attractive alternative to extraction from plants or chemical synthesis. During the past 2 decades, a variety of aldehyde biosynthetic enzymes have undergone detailed characterization. Although metabolic pathways that result in alcohol synthesis via aldehyde intermediates were long known, only recent investigations in model microbes such as Escherichia coli have succeeded in minimizing the rapid endogenous conversion of aldehydes into their corresponding alcohols. Such efforts have provided a foundation for microbial aldehyde synthesis and broader utilization of aldehydes as intermediates for other synthetically challenging biochemical classes. However, aldehyde toxicity imposes a practical limit on achievable aldehyde titers and remains an issue of academic and commercial interest. In this minireview, we summarize published efforts of microbial engineering for aldehyde synthesis, with an emphasis on de novo synthesis, engineered aldehyde accumulation in E. coli, and the challenge of aldehyde toxicity.MIT Synthetic Biology Engineering Research Center (Grant EEC-0540879)National Science Foundation (U.S.). Graduate Research Fellowshi

Rapid in vitro prototyping of O-methyltransferases for pathway applications in Escherichia coli

O-Methyltransferases are ubiquitous enzymes involved in biosynthetic pathways for secondary metabolites such as bacterial antibiotics, human catecholamine neurotransmitters, and plant phenylpropanoids. While thousands of putative O-methyltransferases are found in sequence databases, few examples are functionally characterized. From a pathway engineering perspective, however, it is crucial to know the substrate and product ranges of the respective enzymes to fully exploit their catalytic power. In this study, we developed an in vitro prototyping workflow that allowed us to screen ∼30 enzymes against five substrates in 3 days with high reproducibility. We combined in vitro transcription/translation of the genes of interest with a microliter-scale enzymatic assay in 96-well plates. The substrate conversion was indirectly measured by quantifying the consumption of the S-adenosyl-L-methionine co-factor by time-resolved fluorescence resonance energy transfer rather than time-consuming product analysis by chromatography. This workflow allowed us to rapidly prototype thus far uncharacterized O-methyltransferases for future use as biocatalysts

Using graphical and pictorial representations to teach introductory astronomy students about the detection of extrasolar planets via gravitational microlensing

The detection and study of extrasolar planets is an exciting and thriving field in modern astrophysics, and an increasingly popular topic in introductory astronomy courses. One detection method relies on searching for stars whose light has been gravitationally microlensed by an extrasolar planet. In order to facilitate instructors' abilities to bring this interesting mix of general relativity and extrasolar planet detection into the introductory astronomy classroom, we have developed a new Lecture-Tutorial, "Detecting Exoplanets with Gravitational Microlensing." In this paper, we describe how this new Lecture-Tutorial's representations of astrophysical phenomena, which we selected and created based on theoretically motivated considerations of their pedagogical affordances, are used to help introductory astronomy students develop more expert-like reasoning abilities.Comment: 10 pages, 10 figures, accepted for publication in the American Journal of Physic