Energía libre en la naturaleza

Los rayos del sol generan en la tierra dos energías: eléctrica y térmica, estas en algunos casos generan un desorden y en otros beneficios. Los componentes de la tierra: atmósfera, geósfera e hidrósfera a la observación se analiza que estos están formados por elementos que tienen electrones libres que los componen en la última orbita de las moléculas, que al ser perturbados por los fotones de los rayos del sol generan cambios incalculables en los componentes del globo terráqueo. Con este enunciado,se ha realizado observaciones minuciosas e iterativas a los fenómenos naturales que se presentan en el medio ambiente y plantear teorías del origen de las mismas en base a los electrones libres en la naturaleza

Theory of Volcanic Energy (Expanded English Edition)

When the internal energy converges with the external energy, the external energy moves abruptly (because it is unstable), and if this displacement is through areas with reactive material, then, it can fulfill the function of activation energy and could be the origin of a volcanic combustion. Consequently, volcanoes are the product of geolocated combustion, whose intensity and type of activity depend on the reaction capacity of the components, while the lifetime of the volcano depends on the amount of reactive material

Evidences of autoregulation of hfq expression in Sinorhizobium meliloti strain 2011

Riboregulation comprises gene expression regulatory mechanisms that rely upon the activity of small non-coding RNAs (sRNAs) and in most cases RNA binding proteins. In c-proteobacteria, the Sm-like protein Hfq is a key player in riboregulatory processes, because it promotes sRNA-mRNA interactions and influences mRNA polyadenylation or translation. In the α-proteobacterium Sinorhizobium meliloti, the large number of detected small RNA transcripts and the pleiotropic effects of hfq mutations lead to the hypothesis that riboregulatory mechanisms are important in this soil microorganism to adjust gene expression both in free-living conditions and as a nitrogenfixing endosymbiont within legume root nodules. In this study, homology modeling of S. meliloti Hfq protein and cross-complementation experiments of S. meliloti and Escherichia coli mutants indicates that hfq Sm encodes an RNA chaperone that can be functionally exchanged by its homolog from E. coli. A transcriptional and translational analysis of S. meliloti hfq expression by means of lacZ reporter fusions strongly suggests that the S. meliloti Hfq protein autocontrols its expression at the translational level, a phenomenon that was evident in the natural host S. meliloti as well as in the heterologous host E. coli.Fil: Sobrero, Patricio Martín. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Valverde, Claudio Fabián. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

The Irr and RirA proteins participate in a complex regulatory circuit and act in concert to modulate bacterioferritin expression in Ensifer meliloti 1021

In this work we found that the bfr gene of the rhizobial species Ensifer meliloti, encoding a bacterioferritin iron storage protein, is involved in iron homeostasis and the oxidative stress response. This gene is located downstream of and overlapping the smc03787 open reading frame (ORF). No well-predicted RirA or Irr boxes were found in the region immediately upstream of the bfr gene although two presumptive RirA boxes and one presumptive Irr box were present in the putative promoter of smc03787. We demonstrate that bfr gene expression is enhanced under iron-sufficient conditions and that Irr and RirA modulate this expression. The pattern of bfr gene expression as well as the response to Irr and RirA is inversely correlated to that of smc03787. Moreover, our results suggest that the small RNA SmelC759 participates in RirA- and Irr-mediated regulation of bfr expression and that additional unknown factors are involved in iron-dependent regulation.Fil: Costa, Daniela. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Amarelle, Vanesa. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Valverde, Claudio Fabián. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: O`Brian, Mark R.. State University of New York; Estados UnidosFil: Fabiano, Elena. Instituto de Investigaciones Biológicas "Clemente Estable"; Urugua

The bacterial protein Hfq: Much more than a mere RNA-binding factor

Most of the sequenced bacterial genomes contain a gene encoding a protein known as Hfq that resembles the eukaryotic RNA-binding proteins of the LSm family. It was originally identified in Escherichia coli as a host factor required for replication of the Qβ RNA phage. In this review, we present a comprehensive summary of 40 years of investigation to learn that Hfq is an influential, though not essential, global regulator of gene expression in bacteria and that this feature is undoubtedly linked to Hfq's RNA-binding properties. This protein intervenes in different RNA transactions, notably the promotion of antisense interactions between messenger RNAs and small regulatory RNAs. Yet, several aspects of its molecular mechanism remain not understood. In addition, mechanistic studies have been exclusively carried out in enterobacterial models, highlighting the need to expand the research on Hfq function to other taxons. Upon reviewing the genetic, structural, biochemical, and biological aspects of this extraordinary protein, we discuss recent findings on interactions with macromolecules other than RNA suggesting a broader participation of Hfq in major steps in the flow of genetic information. We show that, although significant progress has been achieved to elucidate Hfq role at the molecular level, many open questions remain.Fil: Sobrero, Patricio Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Valverde, Claudio Fabián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentin

A simple laboratory class using a Pseudomonas aeruginosa auxotroph to illustrate UV-mutagenic killing, DNA photorepair and mutagenic DNA repair

A simple and cheap laboratory class is proposed to illustrate the lethal effect of UV radiation on bacteria and the operation of different DNA repair mechanisms. The class is divided into two sessions, an initial 3-hour experimental session and a second 2-hour analytical session. The experimental session involves two separate experiments: one dedicated to illustrating the lethal effect of UV radiation and the protective effect of DNA photorepair; the second to explore the operation of DNA repair mechanisms that prioritise survival but introduce mutations. The procedure makes use of a Pseudomonas aeruginosa double auxotroph, which serves to detect UV-induced back-mutations to prototrophy. The proposed scheme is carried out by undergraduate students of the Bacterial Physiology and Genetics course, as part of our Biotechnology curriculum. We think that it will be a valuable tool for microbiology students to increase their understanding of basic genetic concepts.Fil: Sobrero, Patricio Martín. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Valverde, Claudio Fabián. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Comparative Genomics and Evolutionary Analysis of RNA-Binding Proteins of the CsrA Family in the Genus Pseudomonas

Gene expression is adjusted according to cellular needs through a combination of mechanisms acting at different layers of the flow of genetic information. At the posttranscriptional level, RNA-binding proteins are key factors controlling the fate of nascent and mature mRNAs. Among them, the members of the CsrA family are small dimeric proteins with heterogeneous distribution across the bacterial tree of life, that act as global regulators of gene expression because they recognize characteristic sequence/structural motifs (short hairpins with GGA triplets in the loop) present in hundreds of mRNAs. The regulatory output of CsrA binding to mRNAs is counteracted in most cases by molecular mimic, non-protein coding RNAs that titrate the CsrA dimers away from the target mRNAs. In γ-proteobacteria, the regulatory modules composed by CsrA homologs and the corresponding antagonistic sRNAs, are mastered by two-component systems of the GacS-GacA type, which control the transcription and the abundance of the sRNAs, thus constituting the rather linear cascade Gac-Rsm that responds to environmental or cellular signals to adjust and coordinate the expression of a set of target genes posttranscriptionally. Within the γ-proteobacteria, the genus Pseudomonas has been shown to contain species with different number of active CsrA (RsmA) homologs and of molecular mimic sRNAs. Here, with the help of the increasing availability of genomic data we provide a comprehensive state-of-the-art picture of the remarkable multiplicity of CsrA lineages, including novel yet uncharacterized paralogues, and discuss evolutionary aspects of the CsrA subfamilies of the genus Pseudomonas, and implications of the striking presence of csrA alleles in natural mobile genetic elements (phages and plasmids).Fil: Sobrero, Patricio Martín. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Centro de Bioquímica y Microbiología de Suelos. Laboratorio de Fisiología, Genética de Bacterias para Plantas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Valverde, Claudio Fabián. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Centro de Bioquímica y Microbiología de Suelos. Laboratorio de Fisiología, Genética de Bacterias para Plantas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Rapid preparation of affinity-purified lipopolysaccharide samples for electrophoretic analysis

Lipopolysaccharides (LPS) are the major components of the outer membrane of gram-negative bacteria. These surface molecules are relevant both for the outer membrane stability and for the interaction of the bacteria with other organisms and with the environment (18). Extensive literature is available concerning LPS physiology in different symbiotic (parasitic) and pathogenic host-bacterial interaction systems (5,20). Physiological, biochemical and chemical approaches to study LPS functions commonly require LPS extraction and purification. In the literature, LPS have been prepared by a number of different cell disruption procedures. Protocols for LPS isolation include organic solvent extractions followed by exhaustive dialysis or evaporation steps, and their modifications (11,22).Facultad de Ciencias Exacta

Role of the stress sigma factor RpoS in GacA/RsmA-controlled secondary metabolism and resistance to oxidative stress in Pseudomonas fluorescens CHA0

In Pseudomonas fluorescens biocontrol strain CHA0, the two-component system GacS/GacA positively controls the synthesis of extracellular products such as hydrogen cyanide, protease, and 2,4-diacetylphloroglucinol, by upregulating the transcription of small regulatory RNAs which relieve RsmA-mediated translational repression of target genes. The expression of the stress sigma factor σS (RpoS) was controlled positively by GacA and negatively by RsmA. By comparison with the wild-type CHA0, both a gacS and an rpoS null mutant were more sensitive to H2O2 in stationary phase. Overexpression of rpoS or of rsmZ, encoding a small RNA antagonistic to RsmA, restored peroxide resistance to a gacS mutant. By contrast, the rpoS mutant showed a slight increase in the expression of the hcnA (HCN synthase subunit) gene and of the aprA (major exoprotease) gene, whereas overexpression of σS strongly reduced the expression of these genes. These results suggest that in strain CHA0, regulation of exoproduct synthesis does not involve σS as an intermediate in the Gac/Rsm signal transduction pathway whereas σS participates in Gac/Rsm-mediated resistance to oxidative stres

Selective enrichment of Pseudomonas spp. in the rhizoplane of different plant species

En contraste con la simbiosis entre rizobios y leguminosas, la especificidad de las pseudomonas en la colonización radicular parece menos estricta. Sin embargo, estudios sobre la diversidad bacteriana del nicho rizosférico resaltan la influencia de la especie vegetal en la selección específica de ciertos microorganismos a partir de la flora residente del suelo. Para evaluar el efecto que los cultivos extensivos de nuestro país tienen sobre la estructura de las comunidades de pseudomonas, se realizaron experimentos con plantas trampa, partiendo de semillas de trigo, maíz y soja, desinfectadas superficialmente y sembradas en un mismo suelo prístino. A partir de las suspensiones representativas de la microflora del rizoplano, se realizaron recuentos en placa en medio selectivo para pseudomonas. El conjunto de colonias de cada muestra se utilizó como fuente de ADN para analizar la estructura de comunidad a través del perfil de restricción de amplicones de los genes oprF y gacA. El análisis comparativo de estos perfiles agrupó a las muestras por especie de planta y las distinguió del patrón obtenido a partir del suelo prístino. La secuenciación parcial del gen 16S ADNr de aislamientos bacterianos representativos confirmó la existencia de genotipos enriquecidos diferencialmente en cada especie vegetal. Estos resultados apoyan la hipótesis de la existencia de mecanismos de selección específica de estirpes de pseudomonas a partir de la flora nativa del suelo en la interacción cooperativa entre estas PGPR y las raíces de diferentes cultivos como trigo, soja y maíz.In contrast to rhizobia-legume symbiosis, the specificity for root colonization by pseudomonads seems to be less strict. However, several studies about bacterial diversity in the rhizosphere highlight the influence of plant species on the selective enrichment of certain microorganisms from the bulk soil community. In order to evaluate the effect that different crops have on the structure of pseudomonad community on the root surface, we performed plant trap experiments, using surface-disinfected maize, wheat or soybean seeds that were sown in pots containing the same pristine soil as substrate. Rhizoplane suspensions were plated on a selective medium for Pseudomonas, and pooled colonies served as DNA source to carry out PCR-RFLP community structure analysis of the pseudomonads-specific marker genes oprF and gacA. PCR-RFLP profiles were grouped by plant species, and were distinguished from those of bulk soil samples. Partial sequencing of 16S rDNA genes of some representative colonies of Pseudomonas confirmed the selective enrichment of distinctive genotypes in the rhizoplane of each plant species. These results support the idea that the root systems of agricultural crops such as soybean, maize and wheat, select differential sets of pseudomonads from the native microbial repertoire inhabiting the bulk soil.Fil: Marrero, Mariana. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Agaras, Betina Cecilia. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wall, Luis Gabriel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Valverde, Claudio Fabián. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin