THERMAL STABILITY OF POWDERED Cu2S

The powder of copper (I) sulphide were synthesized by chemical bath depositions at 298 K from the ammonium system. Thermal-gravimetric studies in argon medium revealed the stability of the analyzed sample Cu2S to thermal destruction in the temperature range 20–180 °C. Heating the powder to 220 °C leads to a phase transition of rhombic α-Cu2S into a hexagonal β-modification.Total loss of mass in the samples after heating up to 600 оC was near 18.52 %

Factores estructurales, bioquímicos y moleculares de la simbiosis Bradyrhizobium sp. (Lupinus)-Lupinus

The present revision summarises some of the original works carried out in our Department to study different aspects of the peculiar symbiosis Bradyrhyzobium sp. Lupinus, by integrating structure and function. The first part of the revision is focused to a structural study on the infection mechanisms, since differ of other legumes. This study was realized by applying immunofluorescent techniques with the green fluorescent protein, immunocytochemistry and different microscopies. It could be observed that the infection by the Bradyrhizobium follows the intercellular way. The infection study includes the presence of enzymatic components, as MAPKs (Mitogen-Activated Protein Kinase) and aldehyde oxidase in the first steps of the symbiosis. Both enzymes are very much related with auxins and cell multiplication. The second part takes up the physiological, biochemical and genetic mechanisms that regulates nitrogen fixation, speccially those related to oxygen diffusion, since nitrogenase activity is very sensible to oxygen and needs a microaerobic atmosphere for its function. Between these mechanisms, the leghemoglobine and the oxygendiffusion resistance barrier have been considered the more important in oxygen regulation. Finally it is included the results of a genetic study carried out to know the genes implicated in nodule oxygen diffusion as: lenod 2, leghemoglobin and nifH.La presente revisión es un resumen de algunos trabajos originales realizados en nuestro Departamento para el estudio de diferentes aspectos de esta peculiar simbiosis, siempre integrando estructura y función. La primera parte está dedicada a un estudio estructural llevado a cabo con el fin de conocer los mecanismos de infección, que difieren de la mayoría de las leguminosas estudiadas. Para este fin se aplicaron técnicas de immunofluorescencia con la green fluorescent protein (GPT), técnicas de inmunocitoquímica y de hibridación in situ. Mediante estos estudios se ha observado que la infección se realiza por vía intercelular. Junto al estudio estructural se describen algunos componentes enzimáticos del nódulo, MAPKinasas (Mitogen-activated protein kinase) y aldehído oxidasa, presentes en estadios tempranos del reconocimiento bacteria-planta. Ambos enzimas están relacionados con la mitosis y la multiplicación de las células radicales. La segunda parte se refiere a los mecanismos fisiológicos, bioquímicos y moleculares que regulan la simbiosis, especialmente los relacionados con la regulación de oxígeno en el nódulo, de gran importancia para la fijación de N2, ya que la nitrogenasa necesita una atmósfera microaeróbica para fijar nitrógeno. Se describen algunos mecanismos de regulación, como la leghemoglobina y la barrera de resistencia a la difusión de O2. Por último también se incluye el estudio genético que realizamos para conocer los genes que regulan la difusión de O2 en el nódulo: lenod 2, leghemoglobin y nifH

Genome sequence of Chlamydophila caviae (Chlamydia psittaci GPIC): examining the role of niche-specific genes in the evolution of the Chlamydiaceae

The genome of Chlamydophila caviae (formerly Chlamydia psittaci, GPIC isolate) (1 173 390 nt with a plasmid of 7966 nt) was determined, representing the fourth species with a complete genome sequence from the Chlamydiaceae family of obligate intracellular bacterial pathogens. Of 1009 annotated genes, 798 were conserved in all three other completed Chlamydiaceae genomes. The C.caviae genome contains 68 genes that lack orthologs in any other completed chlamydial genomes, including tryptophan and thiamine biosynthesis determinants and a ribose-phosphate pyrophosphokinase, the product of the prsA gene. Notable amongst these was a novel member of the virulence-associated invasin/intimin family (IIF) of Gram-negative bacteria. Intriguingly, two authentic frameshift mutations in the ORF indicate that this gene is not functional. Many of the unique genes are found in the replication termination region (RTR or plasticity zone), an area of frequent symmetrical inversion events around the replication terminus shown to be a hotspot for genome variation in previous genome sequencing studies. In C.caviae, the RTR includes several loci of particular interest including a large toxin gene and evidence of ancestral insertion(s) of a bacteriophage. This toxin gene, not present in Chlamydia pneumoniae, is a member of the YopT effector family of type III-secreted cysteine proteases. One gene cluster (guaBA-add) in the RTR is much more similar to orthologs in Chlamydia muridarum than those in the phylogenetically closest species C.pneumoniae, suggesting the possibility of horizontal transfer of genes between the rodent-associated Chlamydiae. With most genes observed in the other chlamydial genomes represented, C.caviae provides a good model for the Chlamydiaceae and a point of comparison against the human atherosclerosis-associated C.pneumoniae. This crucial addition to the set of completed Chlamydiaceae genome sequences is enabling dissection of the roles played by niche-specific genes in these important bacterial pathogens