Effect of Hydrogen Peroxide on the Biosynthesis of Heme and Proteins: Potential Implications for the Partitioning of Glu-tRNA\u3csup\u3eGlu\u3c/sup\u3e Between These Pathways

Glutamyl-tRNA (Glu-tRNAGlu) is the common substrate for both protein translation and heme biosynthesis via the C5 pathway. Under normal conditions, an adequate supply of this aminoacyl-tRNA is available to both pathways. However, under certain circumstances, Glu-tRNAGlu can become scarce, resulting in competition between the two pathways for this aminoacyl-tRNA. In Acidithiobacillus ferrooxidans, glutamyl-tRNA synthetase 1 (GluRS1) is the main enzyme that synthesizes Glu-tRNAGlu. Previous studies have shown that GluRS1 is inactivated in vitro by hydrogen peroxide (H2O2). This raises the question as to whether H2O2 negatively affects in vivo GluRS1 activity in A. ferrooxidans and whether Glu-tRNAGlu distribution between the heme and protein biosynthesis processes may be affected by these conditions. To address this issue, we measured GluRS1 activity. We determined that GluRS1 is inactivated when cells are exposed to H2O2, with a concomitant reduction in intracellular heme level. The effects of H2O2 on the activity of purified glutamyl-tRNA reductase (GluTR), the key enzyme for heme biosynthesis, and on the elongation factor Tu (EF-Tu) were also measured. While exposing purified GluTR, the first enzyme of heme biosynthesis, to H2O2 resulted in its inactivation, the binding of glutamyl-tRNA to EF-Tu was not affected. Taken together, these data suggest that in A. ferrooxidans, the flow of glutamyl-tRNA is diverted from heme biosynthesis towards protein synthesis under oxidative stress conditions

Editorial: Microbial Life Under Stress: Biochemical, Genomic, Transcriptomic, Proteomic, Bioinformatics, Evolutionary Aspects, and Biotechnological Applications of Poly-Extremophilic Bacteria, Volume II

Habitats defined as “extremes” exist across the entire planet. They can be widely different in their physico-chemical features as they include a diverse array of harsh parameters thought to preclude the existence of living organisms, such as temperature, pH, salinity, radiation, pressure, low water activity, low nutrients, and even the presence of toxic agents such as metals and/or metalloids. Organisms capable of surviving or thriving in those habitats are named “extremophiles” and the vast majority of them are prokaryotes, which is not surprising as they show a remarkable reservoir of genomes allowing them to grow in a great variety of hostile niches. Interestingly, several harsh conditions may occur simultaneously and the microorganisms able to withstand them are called “poly-extremophiles”. Although many bacterial species from all kinds of extreme environments have been isolated and described in the last decades, very little is known about the molecular strategies and physiology that allow them to grow in such critical conditions. The aim of this Research Topic on Microbial Life Under Stress (Volume II) is to address this issue by applying multidisciplinary approaches for integrating data from biochemical, genomic, transcriptomic, proteomic, bioinformatics, and evolutionary studies of bacteria from extreme and poly-extreme environments. This Research Topic consists of 14 original articles by numerous authors actively engaged in the study of microbiology, biochemistry, and omic-research of extremophiles. The present Editorial can be divided into four sections which include groups of articles on different genera and species of acidophiles, studies on microorganisms from arid/desiccated environments but also from habitats at low and high temperatures, and finally, a set of papers on extremophiles capable of coping with extreme levels of radiation, pressure, and toxic metals

Draft Genome Sequence of the Iron-Oxidizing AcidophileLeptospirillum ferriphilum Type Strain DSM 14647

The genomic features of the Leptospirillum ferriphilum type strain DSM 14647 are described here. An analysis of the predicted genes enriches our knowledge of the molecular basis of iron oxidation, improves our understanding of its role in industrial bioleaching, and suggests how it is adapted to live at extremely low pH

Comparative genomic analysis of carbon and nitrogen assimilation mechanisms in three indigenous bioleaching bacteria: predictions and validations

<p>Abstract</p> <p>Background</p> <p>Carbon and nitrogen fixation are essential pathways for autotrophic bacteria living in extreme environments. These bacteria can use carbon dioxide directly from the air as their sole carbon source and can use different sources of nitrogen such as ammonia, nitrate, nitrite, or even nitrogen from the air. To have a better understanding of how these processes occur and to determine how we can make them more efficient, a comparative genomic analysis of three bioleaching bacteria isolated from mine sites in Chile was performed. This study demonstrated that there are important differences in the carbon dioxide and nitrogen fixation mechanisms among bioleaching bacteria that coexist in mining environments.</p> <p>Results</p> <p>In this study, we probed that both <it>Acidithiobacillus ferrooxidans </it>and <it>Acidithiobacillus thiooxidans </it>incorporate CO₂via the Calvin-Benson-Bassham cycle; however, the former bacterium has two copies of the Rubisco type I gene whereas the latter has only one copy. In contrast, we demonstrated that <it>Leptospirillum ferriphilum </it>utilizes the reductive tricarboxylic acid cycle for carbon fixation. Although all the species analyzed in our study can incorporate ammonia by an ammonia transporter, we demonstrated that <it>Acidithiobacillus thiooxidans </it>could also assimilate nitrate and nitrite but only <it>Acidithiobacillus ferrooxidans </it>could fix nitrogen directly from the air.</p> <p>Conclusion</p> <p>The current study utilized genomic and molecular evidence to verify carbon and nitrogen fixation mechanisms for three bioleaching bacteria and provided an analysis of the potential regulatory pathways and functional networks that control carbon and nitrogen fixation in these microorganisms.</p

Implementação de um clube de escola de ornitologia no norte semiárido do Chile

The processes of scientific school research with birds allow developing in school-age students the ability to recognize the species from their immediate environment and learn skills of scientific work, being protagonists of their learning; educational experience that is summarized in this article. Between 2015 and 2018 an extracurricular workshop was run with a group of Chilean schoolchildren, to develop a research line with urban birds, whose objectives were to characterize the bird community of the city of La Serena and generate significant appropriation of the scientific work in ecology. The focus was on projects and participation in school and citizen science initiatives. As main results students valued not only birds as objects of study and conservation, but also scientific activity and positively evaluated their process as young researchers. By way of conclusion given the training potential of the present initiative and similar ones that are currently happening in Chile, it is imperative to continue fostering the exchange of experiences and learning among the educators and students involved. This contributes to more significant equity and social justice facing the scientific task that the school generates. &nbsp; &nbsp;Los procesos de investigación científica escolar con aves permiten desarrollar en estudiantes en edad escolar el reconocimiento de especies de su entorno próximo y aprender dinámicas de trabajo científico, al ser protagonistas de sus propios aprendizajes; experiencia educativa que se resume en este artículo. Entre los años 2015 y 2018, se ejecutó un taller extraescolar con un grupo de escolares chilenos y se desarrolló una línea de investigación con aves urbanas, cuyos objetivos fueron caracterizar la comunidad de aves de la ciudad de La Serena y generar apropiación significativa del quehacer científico en ecología. Se trabajó bajo el enfoque de proyectos y la participación en iniciativas de ciencia escolar y ciudadana. Como principales resultados, los estudiantes valoraronno solo las aves como objetos de estudio y conservación, sino también la actividad científica y evaluaron positivamente su propio proceso como jóvenes investigadores. A modo de conclusión, dado el potencial formativo de la presente iniciativa y otras similares que acontecen en la actualidad en Chile, es imperativo seguir propiciando el intercambio de experiencias y aprendizajes entre los educadores y estudiantes involucrados, con miras a contribuir a la mayor equidad y justicia social frente al quehacer científico que se genera en la escuela. &nbsp;Os processos de pesquisa científica escolar com aves permitem que os alunos desenvolvam o reconhecimento de espécies em seu ambiente imediato e aprendam a dinâmica do trabalho científico, sendo protagonistas de sua própria aprendizagem; experiência educacional resumida neste artigo. Entre 2015 e 2018, foi realizada uma oficina extracurricular com um grupo de escolares chilenos e foi desenvolvida uma linha de pesquisa com aves urbanas, cujos objetivos eram caracterizar a comunidade de aves da cidade de La Serena e gerar apropriação significativa do trabalho científico em ecologia. O trabalho foi realizado sob o foco de projetos e participação em iniciativas de ciências escolares e cidadãs. Como principais resultados, os alunos valorizaram não apenas as aves como objetos de estudo e conservação, mas também a atividade científica e avaliaram positivamente seu próprio processo como jovens pesquisadores. Como conclusão, dado o potencial de treinamento desta iniciativa e similares que estão ocorrendo atualmente no Chile, é imperativo continuar promovendo o intercâmbio de experiências e aprendizado entre os educadores e os alunos envolvidos, com vistas a contribuir para maior equidade e justiça social em relação ao trabalho científico gerado na escola. &nbsp

Producción y caracterización de heterobactina B de rhodococcus erythropolis S43 : un sideróforo quelante de arsénico

El arsénico es un metaloide ubicuo, sin embargo, puede convertirse en un contaminante debido a actividades industriales como la minería. Este metaloide es altamente tóxico y un problema ambiental en varios países, entre ellos Chile y Alemania, donde la descontaminación del arsénico es un problema pendiente. Rhodococcus erythropolis S43 es una actinobacteria tolerante al arsénico aislada de un suelo contaminado con el metaloide desde una mina de plata, ubicada cerca de Freiberg, Alemania. Esta cepa es capaz de producir sideróforos cuando se expone a condiciones de carencia de hierro. Este trabajo explora la ruta putativa de producción de sideróforos en R. erythropolis S43 y la capacidad quelante de arsénico de estos compuestos. Para inducir la producción de sideróforos, la cepa se cultivó en medio M9 libre de hierro y la capacidad quelante de hierro y arsénico se evaluó utilizando el ensayo colorimétrico CAS y As-mCAS respectivamente. La actividad quelante obtenida fue expresada en concentración μMEq de desferroxamina B (DFOB). Los metabolitos obtenidos mostraron capacidad quelante hierro y arsénico, logrando una actividad equivalente a 160 μM de DFOB en el extracto crudo y aproximadamente 10 mM de DFOB en un extracto concentrado en 80% metanol. Este último se analizó mediante HPLC, donde mostró un único pico de absorbancia a tiempo de retención de 11,8 minutos, el cual es responsable de la actividad quelante del extracto. Estos hallazgos sugieren que R. erythropolis S43 produce un solo tipo de sideróforo (heterobactina) el cual es capaz de quelar hierro y arsénico. Este resultado abre una nueva perspectiva para enfrentar el problema de la contaminación con arsénico utilizando la capacidad quelante de los sideróforos bacterianosFil: Retamal Morales, Gerardo. Universidad de Santiago de ChileFil: Levicán, Gloria. Universidad de Santiago de ChileFil: Menhert, Marika. Technische Universität Bergakademie FreibergFil: Schlömann, Michael. Technische Universität Bergakademie FreibergFil: Schwabe, Ringo. Technische Universität Bergakademie Freiber

Psychometric properties of the Teachers’ Sense of Efficacy Scale in a sample of Chilean public school teachers

The Teachers’ Sense of Efficacy Scale (TSES) has demonstrated suitable levels of reliability and validity for its use on the teacher population in several countries, and it is the most used scale to assess teachers’ beliefs in their efficacy. However, few psychometric studies exist on its applicability to elementary teachers in public schools. This study analyzed the psychometric properties of the TSES in teachers who work in elementary education. The sample comprised 1,406 Chilean teachers, mainly women (77.2%), from various Chilean public and subsidized schools. The results obtained from three confirmatory factor analyses demonstrated that the model that best fit the data was bifactor exploratory structural equation modeling (B-ESEM) for 24 items, one general factor, and three residual factors. The results of the factorial invariance analysis indicate that the TSES remains stable up to the strict level of invariance for the variable sex. These results imply that the TSES can be used on Chilean teachers. The results are discussed based on the theoretical and empirical evidence available

Structure of an archaeal non-discriminating glutamyl-tRNA synthetase: a missing link in the evolution of Gln-tRNAGln formation

The molecular basis of the genetic code relies on the specific ligation of amino acids to their cognate tRNA molecules. However, two pathways exist for the formation of Gln-tRNAGln. The evolutionarily older indirect route utilizes a non-discriminating glutamyl-tRNA synthetase (ND-GluRS) that can form both Glu-tRNAGlu and Glu-tRNAGln. The Glu-tRNAGln is then converted to Gln-tRNAGln by an amidotransferase. Since the well-characterized bacterial ND-GluRS enzymes recognize tRNAGlu and tRNAGln with an unrelated α-helical cage domain in contrast to the β-barrel anticodon-binding domain in archaeal and eukaryotic GluRSs, the mode of tRNAGlu/tRNAGln discrimination in archaea and eukaryotes was unknown. Here, we present the crystal structure of the Methanothermobacter thermautotrophicus ND-GluRS, which is the evolutionary predecessor of both the glutaminyl-tRNA synthetase (GlnRS) and the eukaryotic discriminating GluRS. Comparison with the previously solved structure of the Escherichia coli GlnRS-tRNAGln complex reveals the structural determinants responsible for specific tRNAGln recognition by GlnRS compared to promiscuous recognition of both tRNAs by the ND-GluRS. The structure also shows the amino acid recognition pocket of GluRS is more variable than that found in GlnRS. Phylogenetic analysis is used to reconstruct the key events in the evolution from indirect to direct genetic encoding of glutamine

Multiple osmotic stress responses in acidihalobacter prosperus result in tolerance to chloride ions

Extremely acidophilic microorganisms (pH optima for growth of =3) are utilized for the extraction of metals from sulfide minerals in the industrial biotechnology of "biomining." A long term goal for biomining has been development of microbial consortia able to withstand increased chloride concentrations for use in regions where freshwater is scarce. However, when challenged by elevated salt, acidophiles experience both osmotic stress and an acidification of the cytoplasm due to a collapse of the inside positive membrane potential, leading to an influx of protons. In this study, we tested the ability of the halotolerant acidophile Acidihalobacter prosperus to grow and catalyze sulfide mineral dissolution in elevated concentrations of salt and identified chloride tolerance mechanisms in Ac. prosperus as well as the chloride susceptible species, Acidithiobacillus ferrooxidans. Ac. prosperus had optimum iron oxidation at 20 g L-1 NaCl while At. ferrooxidans iron oxidation was inhibited in the presence of 6 g L-1 NaCl. The tolerance to chloride in Ac. prosperus was consistent with electron microscopy, determination of cell viability, and bioleaching capability. The Ac. prosperus proteomic response to elevated chloride concentrations included the production of osmotic stress regulators that potentially induced production of the compatible solute, ectoine uptake protein, and increased iron oxidation resulting in heightened electron flow to drive proton export by the F0F1 ATPase. In contrast, At. ferrooxidans responded to low levels of Cl- with a generalized stress response, decreased iron oxidation, and an increase in central carbon metabolism. One potential adaptation to high chloride in the Ac. prosperus Rus protein involved in ferrous iron oxidation was an increase in the negativity of the surface potential of Rus Form I (and Form II) that could help explain how it can be active under elevated chloride concentrations. These data have been used to create a model of chloride tolerance in the salt tolerant and susceptible species Ac. prosperus and At. ferrooxidans, respectively. © 2017 The Authors

Staphylococcus aureus haem biosynthesis and acquisition pathways are linked through haem monooxygenase IsdG

Haem is an essential cofactor in central metabolic pathways in the vast majority of living systems. Prokaryotes acquire haem via haem biosynthesis pathways, and some also utilize haem uptake systems, yet it remains unclear how they balance haem requirements with the paradox that free haem is toxic. Here, using the model pathogen Staphylococcus aureus, we report that IsdG, one of two haem oxygenase enzymes in the haem uptake system, inhibits the formation of haem via the internal haem biosynthesis route. More specifically, we show that IsdG decreases the activity of ferrochelatase and that the two proteins interact both in vitro and in vivo. Further, a bioinformatics analysis reveals that a significant number of haem biosynthesis pathway containing organisms possess an IsdG?homologue and that those with both biosynthesis and uptake systems have at least two haem oxygenases. We conclude that IsdG?like proteins control intracellular haem levels by coupling the two pathways. IsdG is thus a target for the treatment of S. aureusinfections