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The fusion of digits or toes, syndactyly, can be part of complex syndromes, including van der Woude syndrome. A subset of van der Woude cases is caused by dominant-negative mutations in the epithelial transcription factor Grainyhead like-3 (GRHL3), and Grhl3-/-mice have soft-tissue syndactyly. Although impaired interdigital cell death of mesenchymal cells causes syndactyly in multiple genetic mutants, Grhl3-/- embryos had normal interdigital cell death, suggesting alternative mechanisms for syndactyly. We found that in digit separation, the overlying epidermis forms a migrating interdigital epithelial tongue (IET) when the epithelium invaginates to separate the digits. Normally, the non-adhesive surface periderm allows the IET to bifurcate as the digits separate. In contrast, in Grhl3-/- embryos, the IET moves normally between the digits but fails to bifurcate because of abnormal adhesion of the periderm. Our study identifies epidermal developmental processes required for digit separation.

To downregulate gene expression in cyanobacteria, we constructed NOT gate genetic circuits using orthogonal promoters and their cognate repressors regulated translationally by synthetic riboswitches. Four NOT gates were tested and characterized in five cyanobacterial strains using fluorescent reporter-gene assays. In comparison to alternative systems used to downregulate gene expression in cyanobacteria, these NOT gates performed well, reducing YFP reporter expression by 4 to 50-fold. We further evaluated these NOT gates by controlling the expression of the ftsZ gene, which encodes a prokaryotic tubulin homologue that is required for cell division and is essential for Synechococcus elongatus PCC 7942. These NOT gates would facilitate cyanobacterial genetic engineering or the study of essential cellular processes.

Cyanobacteria are photosynthetic bacteria that are currently being developed as biological production platforms. They derive energy from light and carbon from atmospheric carbon dioxide, and some species can fix atmospheric nitrogen. One advantage of developing cyanobacteria for renewable production of biofuels and other biological products is that they are amenable to genetic manipulation, facilitating bioengineering and synthetic biology. To expand the currently available genetic toolkit, we have demonstrated the utility of synthetic theophylline-responsive riboswitches for effective regulation of gene expression in four diverse species of cyanobacteria, including two recent isolates. We evaluated a set of six riboswitches driving the expression of a yellow fluorescent protein reporter in Synechococcus elongatus PCC 7942, Leptolyngbya sp. strain BL0902, Anabaena sp. strain PCC 7120, and Synechocystis sp. strain WHSyn. We demonstrated that riboswitches can offer regulation of gene expression superior to that of the commonly used isopropyl-β-d-thiogalactopyranoside induction of a lacI(q)-Ptrc promoter system. We also showed that expression of the toxic protein SacB can be effectively regulated, demonstrating utility for riboswitch regulation of proteins that are detrimental to biomass accumulation. Taken together, the results of this work demonstrate the utility and ease of use of riboswitches in the context of genetic engineering and synthetic biology in diverse cyanobacteria, which will facilitate the development of algal biotechnology.

The multimeric heteromer, which has mediated signaling, is reassembled and the monomers of the [M.sub.2] muscarinic receptor are purified from Sf9 cells and are incorporated into phospholipid vesicles, both alone and together with G proteins. The results have shown that monomers of the [M.sub.2] receptor can be assembled into tetramers with binding proteins that have resembled with those of the muscarinic receptor in myocardial preparations.

Members of complex microbial communities that reside in environments such as the mammalian gut have evolved mechanisms of interspecies competition, which may be directed at resident microbial and host cells. While previous work has focused mainly on metabolic or niche competition, few specific intermicrobial targeting mechanisms have been elucidated in the mammalian gut. Here, we show that a genotoxin produced by commensal Escherichia coli, colibactin, which was previously shown to induce DNA damage in host intestinal cells, is also able to target via a contact-dependent mechanism a variety of enteric pathogens and commensals, including the important human diarrheal pathogen Vibrio cholerae. We find that colibactin-mediated killing depends on accumulation of intracellular reactive oxygen species, leading to DNA damage and loss of target cell fitness. We also show that the presence of colibactin is associated with cholera outcomes in a large human metagenomic dataset and that colibactin can shape the microbiome by species-specific targeting of a common human gut-associated microbe Bacteroides fragilis, suggesting that genotoxin-mediated mechanisms may have broad effects in the complex polymicrobial interactions that shape commensal microbial communities and their effects on host health and disease. [ABSTRACT FROM AUTHOR]

Summary: Cobamides are a group of compounds including vitamin B12 that can vary at the lower base position of the nucleotide loop. They are synthesized de novo by only a subset of prokaryotes, but some organisms encode partial biosynthesis pathways for converting one variant to another (remodeling) or completing biosynthesis from an intermediate (corrinoid salvaging). Here, we explore the cobamide specificity in Vibrio cholerae through examination of three natural variants representing major cobamide groups: commercially available cobalamin, and isolated pseudocobalamin and p‐cresolylcobamide. We show that BtuB, the outer membrane corrinoid transporter, mediates the uptake of all three variants and the intermediate cobinamide. Our previous work suggested that V. cholerae could convert pseudocobalamin produced by cyanobacteria into cobalamin. In this work, cobamide specificity in V. cholerae is demonstrated by remodeling of pseudocobalamin and salvaging of cobinamide to produce cobalamin. Cobamide remodeling in V. cholerae is distinct from the canonical pathway requiring amidohydrolase CbiZ, and heterologous expression of V. cholerae CobS was sufficient for remodeling. Furthermore, function of V. cholerae cobamide‐dependent methionine synthase MetH was robustly supported by cobalamin and p‐cresolylcobamide, but not pseudocobalamin. Notably, the inability of V. cholerae to produce and utilize pseudocobalamin contrasts with enteric bacteria like Salmonella. [ABSTRACT FROM AUTHOR]

Professional societies can, and should, recruit and retain young scientists by providing a welcoming and inclusive intellectual home. SEEDS (Strategies for Ecology Education, Diversity and Sustainability), the flagship education program of the Ecological Society of America, is designed to broaden participation in ecology through mentoring, field trips, leadership development, and research fellowships. Nationally, fewer than 40% of college students who intended to pursue a career in science, technology, math, or engineering complete their degrees in these fields, and these numbers are even smaller for underrepresented minorities (URMs). In contrast, 80% of SEEDS alumni in our study had completed at least one degree in an ecology-related field, and the completion rate for URMs was 85%. In addition, 71% of working SEEDS alumni respondents have careers in ecology. SEEDS is a model for other professional societies wishing to increase students’ self-efficacy and sense of belonging through professional development and positive social reinforcement. [ABSTRACT FROM AUTHOR]