Molecular and physiological logics of the pyruvate-induced response of a novel transporter in Bacillus subtilis

At the heart of central carbon metabolism, pyruvate is a pivotal metabolite in all living cells. Bacillus subtilis is able to excrete pyruvate as well as to use it as the sole carbon source. We herein reveal that ysbAB (renamed pftAB), the only operon specifically induced in pyruvate-grown B. subtilis cells, encodes a heterooligomeric membrane complex which operates as a facilitated transport system specific for pyruvate, thereby defining a novel class of transporter. We demonstrate that the LytST two-component system is responsible for the induction of pftAB in the presence of pyruvate by binding of the LytT response regulator to a palindromic region upstream of pftAB. We show that both glucose and malate, the preferred carbon sources for B. subtilis, trigger the binding of CcpA upstream of pftAB, which results in its catabolite repression. However, an additional CcpA-independent mechanism represses pftAB in the presence of malate. Screening a genome-wide transposon mutant library, we find that an active malic enzyme replenishing the pyruvate pool is required for this repression. We next reveal that the higher the influx of pyruvate, the stronger the CcpA-independent repression of pftAB, which suggests that intracellular pyruvate retroinhibits pftAB induction via LytST. Such a retroinhibition challenges the rational design of novel nature-inspired sensors and synthetic switches but undoubtedly offers new possibilities for the development of integrated sensor/controller circuitry. Overall, we provide evidence for a complete system of sensors, feed-forward and feedback controllers that play a major role in environmental growth of B. subtilis. [br/] IMPORTANCE Pyruvate is a small-molecule metabolite ubiquitous in living cells. Several species also use it as a carbon source as well as excrete it into the environment. The bacterial systems for pyruvate import/export have yet to be discovered. Here, we identified in the model bacterium Bacillus subtilis the first import/export system specific for pyruvate, PftAB, which defines a novel class of transporter. In this bacterium, extracellular pyruvate acts as the signal molecule for the LytST two-component system (TCS), which in turn induces expression of PftAB. However, when the pyruvate influx is high, LytST activity is drastically retroinhibited. Such a retroinhibition challenges the rational design of novel nature-inspired sensors and synthetic switches but undoubtedly offers new possibilities for the development of integrated sensor/controller circuitry

Repercussões satíricas dos processos de escolarização do social nas ondas do rádio (1930-1940) Satirical repercussions of the social schooling processes in radio programs (1930-1940)

Este artigo analisa repercussões satíricas dos processos de escolarização do social no Brasil, presentes em antigos programas humorísticos de rádio, que, geralmente organizados pelo diálogo entre um professor e seus alunos, foram simultaneamente grandes sucessos em termos de audiência e alvos de uma crítica sistemática por parte daqueles que defendiam a radiodifusão como instrumento de divulgação da "verdadeira" cultura. Por meio do uso de fontes sonoras e impressas, objetiva compreender as razões do sucesso do gênero e, neste percurso, identificar as críticas à escola, à educação e seus sujeitos, que, jocosamente, veicularam, explicitadas em conflitos entre sonoras tradições populares e saberes escolares.<br>This article analyzes satirical repercussions of the social schooling processes in Brazil found in old radio comedies which, usually built around the dialogue between a teacher and his or her students, were, on the one hand, huge audience successes and, on the other hand, subjected to systematic criticism from those who believed that radio broadcasting should be used as an instrument to disseminate the "true" culture. Through the use of sound and print records, the text seeks to understand the reasons behind the success of this genre and, in so doing, to identify the criticisms that these programs directed through humor at the school, at education and its agents, which were brought forward in conflicts between sonorous popular traditions and school knowledge