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

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

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

Effect of hydrogen peroxide on the biosynthesis of heme and proteins: Potential implications for the partitioning of Glu-tRNAGlu between these pathways

© 2014 by the authors; licensee MDPI, Basel, Switzerland. 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

Cold-active pectinolytic activity produced by filamentous fungi associated with Antarctic marine sponges

BACKGROUND: Pectinase enzymes catalyze the breakdown of pectin, a key component of the plant cell wall. At industrial level, pectinases are used in diverse applications, especially in food-processing industry. Currently, most of the industrial pectinases have optimal activity at mesophilic temperatures. On the contrary, very little is known about the pectinolytic activities from organisms from cold climates such as Antarctica. In this work, 27 filamentous fungi isolated from marine sponges collected in King George Island, Antarctica, were screened as new source of cold-active pectinases. RESULTS: In semi-quantitative plate assays, 8 out 27 of these isolates showed pectinolytic activities at 15 °C and one of them, Geomyces sp. strain F09-T3-2, showed the highest production of pectinases in liquid medium containing pectin as sole carbon source. More interesting, Geomyces sp. F09-T3-2 showed optimal pectinolytic activity at 30 °C, 10 °C under the temperature of currently available commer

Comparative genomics of the proteostasis network in extreme acidophiles.

Extreme acidophiles thrive in harsh environments characterized by acidic pH, high concentrations of dissolved metals and high osmolarity. Most of these microorganisms are chemolithoautotrophs that obtain energy from low redox potential sources, such as the oxidation of ferrous ions. Under these conditions, the mechanisms that maintain homeostasis of proteins (proteostasis), as the main organic components of the cells, are of utmost importance. Thus, the analysis of protein chaperones is critical for understanding how these organisms deal with proteostasis under such environmental conditions. In this work, using a bioinformatics approach, we performed a comparative genomic analysis of the genes encoding classical, periplasmic and stress chaperones, and the protease systems. The analysis included 35 genomes from iron- or sulfur-oxidizing autotrophic, heterotrophic, and mixotrophic acidophilic bacteria. The results showed that classical ATP-dependent chaperones, mostly folding chaperones, are widely distributed, although they are sub-represented in some groups. Acidophilic bacteria showed redundancy of genes coding for the ATP-independent holdase chaperones RidA and Hsp20. In addition, a systematically high redundancy of genes encoding periplasmic chaperones like HtrA and YidC was also detected. In the same way, the proteolytic ATPase complexes ClpPX and Lon presented redundancy and broad distribution. The presence of genes that encoded protein variants was noticeable. In addition, genes for chaperones and protease systems were clustered within the genomes, suggesting common regulation of these activities. Finally, some genes were differentially distributed between bacteria as a function of the autotrophic or heterotrophic character of their metabolism. These results suggest that acidophiles possess an abundant and flexible proteostasis network that protects proteins in organisms living in energy-limiting and extreme environmental conditions. Therefore, our results provide a means for understanding the diversity and significance of proteostasis mechanisms in extreme acidophilic bacteria

Differential expression of two bc1 complexes in the strict acidophilic chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans suggests a model for their respective roles in iron or sulfur oxidation

Three strains of the strict acidophilic chemolithoautotrophic Acidithiobacillus ferrooxidans, including the type strain ATCC 23270, contain a petllABC gene cluster that encodes the three proteins, cytochrome c1, cytochrome b and a Rieske protein, that constitute a bc1, electron-transfer complex. RT-PCR and Northern blotting show that the petllABC cluster is co-transcribed with cycA, encoding a cytochrome c belonging to the c4 family, sdrA, encoding a putative short-chain dehydrogenase, and hip, encoding a high potential iron-sulfur protein, suggesting that the six genes constitute an operon, termed the petll operon. Previous results indicated that A. ferrooxidans contains a second pet operon, termed the petl operon, which contains a gene cluster that is similarly organized except that it lacks hip. Real-time PCR and Northern blot experiments demonstrate that petl is transcribed mainly in cells grown in medium containing iron, whereas petll is transcribed in cells grown in media contai