The adaptive mechanism of halophilic Brachybacterium muris in response to salt stress and its mitigation of copper toxicity in hydroponic plants.

Serious environmental pollution of heavy metals has attracted people's attention in recent years and halophiles seem to be potential bioremediation in the controlling of heavy metals contamination. In this study, the adaptive mechanism of halophilic Brachybacterium muris (B. muris) in response to salt stress and its mitigation of copper (Cu) toxicity in hydroponic plants were investigated. The cell morphology was observed using transmission electron microscopy. The cell membrane composition and fluidity were examined by the combination of gas chromatography, gas chromatography-mass spectrometry, ultra-high performance liquid chromatography-mass spectrometry, and fluorescence spectrophotometry. Moreover, the metabolic pathways of B. muris in response to salt stress were analyzed using the prokaryotic transcriptomics approach. A hydroponic co-culture model was further conducted to explore the effects of B. muris on wheat seedlings subjected to Cu toxicity. It was found that B. muris can respond to high osmotic pressure by improving the cell membrane fluidity, altering the cell morphology and cell membrane compositions. The proportion of unsaturated fatty acids, phosphatidylethanolamine, and phosphatidylinositol in B. muris cell membranes increased significantly, while zymosterol, fecosterol, and ergosterol contents decreased under a high salinity situation. Further transcriptomic analysis showed that genes encoding L-glutamate synthase, glutamate ABC transporter ATP-binding protein, and sodium cotransporter were up-regulated, indicating that both the synthesis and transport of glutamate were significantly enhanced under high osmotic pressure. Additionally, B. muris alleviated the inhibitory effect of Cu2+ on wheat seedlings' growth, causing a 30.14% decrease in H2O2 content and a significant increase of 83.86% and 45.96% in POD activity and GSH content in wheat roots, respectively. The findings of this study suggested that the salt-tolerant B. muris may serve as a promising strategy for improving the bioremediation of metal-contaminated saline water and soils.

Alhagi sparsifolia acclimatizes to saline stress by regulating its osmotic, antioxidant, and nitrogen assimilation potential.

BACKGROUND: Alhagi sparsifolia (Camelthorn) is a leguminous shrub species that dominates the Taklimakan desert's salty, hyperarid, and infertile landscapes in northwest China. Although this plant can colonize and spread in very saline soils, how it adapts to saline stress in the seedling stage remains unclear so a pot-based experiment was carried out to evaluate the effects of four different saline stress levels (0, 50, 150, and 300 mM) on the morphological and physio-biochemical responses in A. sparsifolia seedlings. RESULTS: Our results revealed that N-fixing A. sparsifolia has a variety of physio-biochemical anti-saline stress acclimations, including osmotic adjustments, enzymatic mechanisms, and the allocation of metabolic resources. Shoot-root growth and chlorophyll pigments significantly decreased under intermediate and high saline stress. Additionally, increasing levels of saline stress significantly increased Na+ but decreased K+ concentrations in roots and leaves, resulting in a decreased K+/Na+ ratio and leaves accumulated more Na + and K + ions than roots, highlighting their ability to increase cellular osmolarity, favouring water fluxes from soil to leaves. Salt-induced higher lipid peroxidation significantly triggered antioxidant enzymes, both for mass-scavenging (catalase) and cytosolic fine-regulation (superoxide dismutase and peroxidase) of H2O2. Nitrate reductase and glutamine synthetase/glutamate synthase also increased at low and intermediate saline stress levels but decreased under higher stress levels. Soluble proteins and proline rose at all salt levels, whereas soluble sugars increased only at low and medium stress. The results show that when under low-to-intermediate saline stress, seedlings invest more energy in osmotic adjustments but shift their investment towards antioxidant defense mechanisms under high levels of saline stress. CONCLUSIONS: Overall, our results suggest that A. sparsifolia seedlings tolerate low, intermediate, and high salt stress by promoting high antioxidant mechanisms, osmolytes accumulations, and the maintenance of mineral N assimilation. However, a gradual decline in growth with increasing salt levels could be attributed to the diversion of energy from growth to maintain salinity homeostasis and anti-stress oxidative mechanisms.

La tuberculosis no es una enfermedad del pasado / Tuberculosis is not an illness of the past

La búsqueda de una cura para la tuberculosis a lo largo de la historia se ha visto amenazada por la explosión del número de enfermos de VIH y la aparición continuada de resistencias a los fármacos antituberculosos. En esta revisión se comenta el desarrollo de distintos métodos de diagnóstico, vacunas y fármacos, haciendo énfasis en los modos de superar las resistencias, los mecanismos de acción de los fármacos, y las dianas más conocidas o más vulnerables

The search for a cure for tuberculosis throughout history has been menaced by the increasing number of people with HIV and the continuous appearence of antituberculosis drug resistance. The development of diagnosis procedures, vaccines and drugs is updated in this review, emphasizing the methods to overcome resistances, the mechanisms of drugs action, and the best known or more vulnerable targets

Role of TnrA in nitrogen source-dependent repression of Bacillus subtilis glutamate synthase gene expression.

Synthesis of glutamate, the cell's major donor of nitrogen groups and principal anion, occupies a significant fraction of bacterial metabolism. In Bacillus subtilis, the gltAB operon, encoding glutamate synthase, requires a specific positive regulator, GltC, for its expression. In addition, the gltAB operon was shown to be repressed by TnrA, a regulator of several other genes of nitrogen metabolism and active under conditions of ammonium (nitrogen) limitation. TnrA was found to bind directly to a site immediately downstream of the gltAB promoter. As is true for other genes, the activity of TnrA at the gltAB promoter was antagonized by glutamine synthetase under certain growth conditions.