Thioredoxin A regulates protein synthesis to maintain carbon and nitrogen partitioning in cyanobacteria.

Thioredoxins play an essential role in regulating enzyme activity in response to environmental changes, especially in photosynthetic organisms. They are crucial for metabolic regulation in cyanobacteria, but the key redox-regulated central processes remain to be determined. Physiological, metabolic, and transcriptomic characterization of a conditional mutant of the essential Synechocystis sp. PCC 6803 thioredoxin trxA gene (STXA2) revealed that decreased TrxA levels alter cell morphology and induce a dormant-like state. Furthermore, TrxA depletion in the STXA2 strain inhibited protein synthesis and led to changes in amino acid pools and nitrogen/carbon reserve polymers, accompanied by oxidation of the EF-Tu elongation factor. Transcriptomic analysis of TrxA depletion in STXA2 revealed a robust transcriptional response. Down-regulated genes formed a large cluster directly related to photosynthesis, ATP synthesis, and CO2 fixation. In contrast, up-regulated genes were grouped into different clusters related to respiratory electron transport, carotenoid biosynthesis, amino acid metabolism, and protein degradation, among others. These findings highlight the complex regulatory mechanisms that govern cyanobacterial metabolism, where TrxA acts as a critical regulator that orchestrates the transition from anabolic to maintenance metabolism and regulates carbon and nitrogen balance.

Discrete magma injections drive the 2021 La Palma eruption.

Understanding the drivers of the onset, evolution, and end of eruptions and their impact on eruption style is critical in eruption forecasting and emergency management. The composition of erupted liquids is a key piece of the volcano puzzle, but untangling subtle melt variations remains an analytical challenge. Here, we apply rapid, high-resolution matrix geochemical analysis on samples of known eruption date spanning the entire 2021 La Palma eruption. Sr isotope signatures reveal distinct pulses of basanite melt driving the onset, restart, and evolution of the eruption. Elemental variations in matrix and microcrysts track progressive invasion, and draining, of a subcrustal crystal mush. Associated variations in lava flow rate, vent development, seismicity, and SO2 emission demonstrate that volcanic matrix resolves eruption patterns that could be expected in future basaltic eruptions globally.

Exploring the Diversity of the Thioredoxin Systems in Cyanobacteria.

Cyanobacteria evolved the ability to perform oxygenic photosynthesis using light energy to reduce CO2 from electrons extracted from water and form nutrients. These organisms also developed light-dependent redox regulation through the Trx system, formed by thioredoxins (Trxs) and thioredoxin reductases (TRs). Trxs are thiol-disulfide oxidoreductases that serve as reducing substrates for target enzymes involved in numerous processes such as photosynthetic CO2 fixation and stress responses. We focus on the evolutionary diversity of Trx systems in cyanobacteria and discuss their phylogenetic relationships. The study shows that most cyanobacteria contain at least one copy of each identified Trx, and TrxA is the only one present in all genomes analyzed. Ferredoxin thioredoxin reductase (FTR) is present in all groups except Gloeobacter and Prochlorococcus, where there is a ferredoxin flavin-thioredoxin reductase (FFTR). Our data suggest that both TRs may have coexisted in ancestral cyanobacteria together with other evolutionarily related proteins such as NTRC or DDOR, probably used against oxidative stress. Phylogenetic studies indicate that they have different evolutionary histories. As cyanobacteria diversified to occupy new habitats, some of these proteins were gradually lost in some groups. Finally, we also review the physiological relevance of redox regulation in cyanobacteria through the study of target enzymes.

Dark side of cyanobacteria: searching for strategies to control blooms.

Cyanobacteria are ecologically one of the most prolific groups of photosynthetic prokaryotes in marine and freshwater habitats. They are primary producer microorganisms and are involved in the production of important secondary metabolites, including toxic compounds such as cyanotoxins. Environmental conditions promote massive growth of these microbes, causing blooms that can have critical ecological and public health implications. In this highlight, we discuss some of the approaches being addressed to prevent these blooms, such as control of nutrient loading, treatments to minimize growth or monitoring interactions with other species.

Depletion of m-type thioredoxin impairs photosynthesis, carbon fixation, and oxidative stress in cyanobacteria.

Thioredoxins (Trxs) are disulfide oxidoreductases that regulate many biological processes. The m-type thioredoxin (TrxA) is the only Trx present in all oxygenic photosynthetic organisms. Extensive biochemical and proteomic analyses have identified many TrxA target proteins in different photosynthetic organisms. However, the precise function of this essential protein in vivo is still poorly known. In this study, we generated a conditional Synechocystis sp. PCC 6803 mutant strain (STXA2) using an on-off promoter that is able to survive with only 2% of the TrxA level of the wild-type (WT) strain. STXA2 characterization revealed that TrxA depletion results in growth arrest and pronounced impairment of photosynthesis and the Calvin-Benson-Bassham (CBB) cycle. Analysis of the in vivo redox state of the bifunctional enzyme fructose-1,6-bisphosphatase/sedoheptulose-1,7-bisphosphatase showed higher levels of oxidation that affected enzyme activity in STXA2. This result implies that TrxA-mediated redox regulation of the CBB cycle is conserved in both cyanobacteria and chloroplasts, although the targets have different evolutionary origins. The STXA2 strain also accumulated more reactive oxygen species and was more sensitive to oxidative stress than the WT. Analysis of the in vivo redox state of 2-Cys peroxiredoxin revealed full oxidation, corresponding with TrxA depletion. Overall, these results indicate that depletion of TrxA in STXA2 greatly alters the cellular redox state, interfering with essential processes such as photosynthetic machinery operativity, carbon assimilation, and oxidative stress response. The TrxA regulatory role appears to be conserved along the evolution of oxygenic photosynthetic organisms.

Fighting the enemy: one health approach against microbial resistance.

This article highlights publications in Enviromental Microbiology and Microbial Biotechnology papers about antibiotic resistance. It concludes that the One health approach is basic to addressing this problem.

Metals in cyanobacteria: analysis of the copper, nickel, cobalt and arsenic homeostasis mechanisms.

Traces of metal are required for fundamental biochemical processes, such as photosynthesis and respiration. Cyanobacteria metal homeostasis acquires an important role because the photosynthetic machinery imposes a high demand for metals, making them a limiting factor for cyanobacteria, especially in the open oceans. On the other hand, in the last two centuries, the metal concentrations in marine environments and lake sediments have increased as a result of several industrial activities. In all cases, cells have to tightly regulate uptake to maintain their intracellular concentrations below toxic levels. Mechanisms to obtain metal under limiting conditions and to protect cells from an excess of metals are present in cyanobacteria. Understanding metal homeostasis in cyanobacteria and the proteins involved will help to evaluate the use of these microorganisms in metal bioremediation. Furthermore, it will also help to understand how metal availability impacts primary production in the oceans. In this review, we will focus on copper, nickel, cobalt and arsenic (a toxic metalloid) metabolism, which has been mainly analyzed in model cyanobacterium Synechocystis sp. PCC 6803.

Un caso de osteomielitis tuberculosa de clivus / A rare case of tuberculous clivus osteomyelitis

Se presenta un caso de infección tuberculosa con osteomielitis de clivus con afectación de tejidos vecinos y debut como cefalea refractaria sin clínica pulmonar. La osteomielitis tuberculosa de clivus es una entidad descrita en la literatura de forma excepcional y más propia de áreas con alta prevalencia de tuberculosis. Este caso debutó con clínica neurológica poco específica y se llegó al diagnóstico por el resultado del estudio microbiológico de nódulos pulmonares coexistentes sin clínica pulmonar asociada.

We report a case of tuberculous infection of exceptional location: clivus with involvement of surrounding tissues and refractory headache without pulmonary clinic. Tuberculous osteomyelitis of the clivus is a rare entity described in areas with highest tuberculosis prevalence. This case debuts with unspecific neurological symptoms and was diagnosed by the results of microbiological study of coexisting pulmonary nodules, without associated pulmonary clinic.

Comparative genomic analysis of solvent extrusion pumps in Pseudomonas strains exhibiting different degrees of solvent tolerance.

Organic solvents are inherently toxic for microorganisms. Their effects depend not only on the nature of the compound, but also on the intrinsic tolerance of the bacterial species and strains. Three efflux pumps belonging to the RND (resistance-nodulation-cell division) family of multidrug extrusion pumps are the main factor involved in the high intrinsic tolerance to toluene of Pseudomonas putida DOT-T1E. We have analyzed the tolerance to toluene shocks [0.1% and 0.3% (v/v)] of a number of strains belonging to different species of the genus Pseudomonas upon growth in the absence and in the presence of sublethal concentrations of toluene. The strains can be grouped in three categories: (1) highly resistant strains, in which almost 100% of the cells precultured in the presence of sublethal concentrations of toluene withstood a 0.3% (v/v) toluene shock, (2) moderately resistant strains, in which only a fraction (10(-4)-1) of the cells withstood a 0.1% (v/v) toluene shock, but fewer than 1 in 10(7) cells survived a sudden 0.3% (v/v) toluene shock regardless of the growth conditions, and (3) sensitive strains, in which regardless of the growth conditions fewer than 10(-5) cells survived a 0.1% (v/v) toluene shock. We also studied the number and type of efflux pumps in different strains in comparison with the P. putida DOT-T1E strain.