BackgroundViolacein is a deep violet compound that is produced by a number of bacterial species. It is synthesized from tryptophan by a pathway that involves the sequential action of 5 different enzymes (encoded by genes vioA to vioE). Violacein has antibacterial, antiparasitic, and antiviral activities, and also has the potential of inducing apoptosis in certain cancer cells.ResultsHere, we describe the construction of a series of plasmids harboring the complete or partial violacein biosynthesis operon and their use to enable production of violacein and deoxyviolacein in E.coli. We performed in vitro assays to determine the biological activity of these compounds against Plasmodium, Trypanosoma, and mammalian cells. We found that, while deoxyviolacein has a lower activity against parasites than violacein, its toxicity to mammalian cells is insignificant compared to that of violacein.ConclusionsWe constructed E. coli strains capable of producing biologically active violacein and related compounds, and propose that deoxyviolacein might be a useful starting compound for the development of antiparasite drugs.Electronic supplementary materialThe online version of this article (10.1186/s12896-018-0428-z) contains supplementary material, which is available to authorized users.

Difficult conversations are a necessary part of everyday life. To help children, employees, and partners learn and improve, parents, managers, and significant others are frequently tasked with the unpleasant job of delivering negative news and critical feedback. Despite the long-term benefits of these conversations, communicators approach them with trepidation, in part, because they perceive them as involving intractable moral conflict between being honest and being kind. In this article, we review recent research on egocentrism, ethics, and communication to explain why communicators overestimate the degree to which honesty and benevolence conflict during difficult conversations, document the conversational missteps people make as a result of this erred perception, and propose more effective conversational strategies that honor the long-term compatibility of honesty and benevolence. This review sheds light on the psychology of moral tradeoffs in conversation, and provides practical advice on how to deliver unpleasant information in ways that improve recipients' welfare.

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Self-promotion is common in everyday life. Yet, across 8 studies (N = 1,687) examining a broad range of personal and professional successes, we find that individuals often hide their successes from others and that such hiding has relational costs. We document these effects among close relational partners, acquaintances, and within hypothetical relationships. Study 1 finds that targets feel less close to and more insulted by communicators who hide rather than share their successes. Study 2 finds that hiding success harms relationships both when the success is eventually discovered and when it is not. Studies 3 and 4 explore the mechanism underlying these relational costs: Targets infer that communicators have paternalistic motives when they hide their success, which leads them to feel insulted. Studies 5–7 explore the contextual cues that elicit inferences of paternalistic motives, such as private (vs. public) settings (Study 5), direct (vs. indirect) questions (Study 6), and close (vs. distant) relationships (Study 7). Across our studies, we also explore the emotional and impression-management consequences of hiding success. Although the relational consequences of hiding success are universally negative, the emotional and impression-management consequences are mixed. Whereas previous research highlights the negative consequences of sharing one’s accomplishments with others, we find that sharing is superior to hiding for maintaining one’s relationships. Thus, we shed new light on the consequences of paternalism and the relational costs of hiding information in everyday communication.

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