Production of selenium nanoparticles occurs through an interconnected pathway of sulphur metabolism and oxidative stress response in Pseudomonas putida KT2440.

The soil bacterium Pseudomonas putida KT2440 has been shown to produce selenium nanoparticles aerobically from selenite; however, the molecular actors involved in this process are unknown. Here, through a combination of genetic and analytical techniques, we report the first insights into selenite metabolism in this bacterium. Our results suggest that the reduction of selenite occurs through an interconnected metabolic network involving central metabolic reactions, sulphur metabolism, and the response to oxidative stress. Genes such as sucA, D2HGDH and PP_3148 revealed that the 2-ketoglutarate and glutamate metabolism is important to convert selenite into selenium. On the other hand, mutations affecting the activity of the sulphite reductase decreased the bacteria's ability to transform selenite. Other genes related to sulphur metabolism (ssuEF, sfnCE, sqrR, sqr and pdo2) and stress response (gqr, lsfA, ahpCF and sadI) were also identified as involved in selenite transformation. Interestingly, suppression of genes sqrR, sqr and pdo2 resulted in the production of selenium nanoparticles at a higher rate than the wild-type strain, which is of biotechnological interest. The data provided in this study brings us closer to understanding the metabolism of selenium in bacteria and offers new targets for the development of biotechnological tools for the production of selenium nanoparticles.

Motor cortex tDCS does not improve strength performance in healthy subjects / ETCC sobre o córtex motor não aumenta o desempenho de força em sujeitos saudáveis / tDCS en motor corteza no aumenta el rendimiento de fuerza en sujetos sanos

The influence of transcranial direct current stimulation (tDCS) upon maximal strength performance in exercises recruiting large muscle mass has not been established in healthy populations. The purpose of this study was to investigate whether anodal tDCS was able to increase the performance during maximal strength exercise (MSEX) in healthy subjects. Fourteen volunteers (age: 26 ± 4 yrs) performed two MSEX after anodal or sham tDCS (2mA; 20min prior MSEX), involving knee extensors and flexors in concentric isokinetic muscle actions of the dominant limb (3 sets of 10 repetitions). The electrical muscle activity (sEMG) of four recruited muscles was recorded during MSEX. Anodal tDCS was not able to improve force production (i.e., total work and peak torque), fatigue resistance, or electromyographic activity during MSEX when compared to sham condition. In conclusion, anodal tDCS applied upon the contralateral motor cortex was not capable of increasing the strength performance of knee extensors and flexors in young healthy subjects.

A influência da estimulação transcraniana por corrente contínua (ETCC) sobre o desempenho da força muscular em exercícios que recrutam grandes massas musculares ainda não foi estabelecido em populações saudáveis. O objetivo desse estudo foi investigar se a ETCC anódica seria capaz de aumentar o desempenho durante exercício máximo de força (EMF) em sujeitos saudáveis. Catorze voluntários (idade: 26 ± 4 anos) executaram dois EMF com aplicação prévia da ETCC anódica ou placebo (2mA; 20 mim), envolvendo músculos flexores e extensores do joelho dominante em ação concêntrica isocinética (3 séries de 10 repetições). A atividade elétrica muscular (sEMG) de quatro músculos recrutados foi registrada durante o EMF. A ETCC anódica não foi capaz de melhorar a produção de força (trabalho total e pico de torque), resistência à fadiga ou atividade eletromiográfica durante o EMF, quando comparada à condição placebo. Em conclusão, a ETCC anódica aplicada sobre o córtex motor contralateral não foi capaz de aumentar o desempenho de força de flexores e extensores de joelho em jovens saudáveis.

La influencia de estimulación transcraneal de corriente directa (tDCS) en ejercicios de fuerza muscular de rendimiento que reclutan grandes masas musculares no se ha establecido en la población sana. El objetivo de este estudio fue investigar si la ETCC anódica podría mejorar el rendimiento durante el ejercicio máximo de la fuerza (EMF) en sujetos sanos. Catorce voluntarios (26 ± 4 años de edad) realizaron dos EMF con la aplicación previa de ETCC anódica y placebo (2 mA, 20 i) la participación de los flexores y extensores de la rodilla dominante en acción concéntrica (3 series de 10 repeticiones). La actividad eléctrica muscular (sEMG) en cuatro músculos reclutados se registró durante el EMF. La ETCC anódica no fue capaz de mejorar la potencia de salida (trabajo total y pico de torque), la resistencia a la fatiga o la actividad electromiográfica durante el EMF, cuando comparada con la condición placebo. Por lo tanto, la ETCC anódica aplicada a la corteza motora contralateral no fue capaz de aumentar el rendimiento de la fuerza de flexores y extensores de la rodilla en jóvenes sanos.