RESUMEN
The utilization of iridium is expected to surge in the next few years, notably due to the rising implementation of water electrolyzer devices in the energy transition. However, the natural resources of this noble metal are extremely limited and thus its recycling will become of high importance. Unfortunately, iridium is also the most corrosion resistant platinum group metal, making its recovery from waste a difficult and energy-demanding process. Hereby, we study the impact of organics and chloride ions on the electrochemical dissolution of iridium in order to pave the way towards green recycling of this precious metal. We present a 40 times increased dissolution when cycling iridium in presence of HCl and 1 M ethanol compared to HClO4. Our results point towards the direction of destabilizing Ir at relatively mild conditions in acidic media.
RESUMEN
The plasma membrane H+-ATPase couples ATP hydrolysis to proton transport, thereby establishing the driving force for solute transport across the plasma membrane. In Nicotiana plumbaginifolia, this enzyme is encoded by at least nine pma (plasma membrane H+-ATPase) genes. Four of these are classified into two gene subfamilies, pma1-2-3 and pma4, which are the most highly expressed in plant species. We have isolated genomic clones for pma2 and pma4. Mapping of their transcript 5' end revealed the presence of a long leader that contained small open reading frames, regulatory features typical of other pma genes. The gusA reporter gene was then used to determine the expression of pma2, pma3 and pma4 in N. tabacum. These data, together with those obtained previously for pma1, led to the following conclusions. (i) The four pma-gusA genes were all expressed in root, stem, leaf and flower organs, but each in a cell-type specific manner. Expression in these organs was confirmed at the protein level, using subfamily-specific antibodies. (ii) pma4-gusA was expressed in many cell types and notably in root hair and epidermis, in companion cells, and in guard cells, indicating that in N. plumbaginifolia the same H+-ATPase isoform might be involved in mineral nutrition, phloem loading and control of stomata aperture. (iii) The second gene subfamily is composed, in N. plumbaginifolia, of a single gene (pma4) with a wide expression pattern and, in Arabidopsis thaliana, of three genes (aha1, aha2, aha3), at least two of them having a more restrictive expression pattern. (iv) Some cell types expressed pma2 and pma4 at the same time, which encode H+-ATPases with different enzymatic properties.
Asunto(s)
Regulación Enzimológica de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Nicotiana/enzimología , Plantas Tóxicas , ATPasas de Translocación de Protón/genética , Secuencia de Aminoácidos , Secuencia de Bases , Clonación Molecular , ADN de Plantas , Histocitoquímica , Datos de Secuencia Molecular , Familia de Multigenes , ATPasas de Translocación de Protón/metabolismo , ARN Mensajero/genéticaRESUMEN
The sequence of a verocytotoxin 2 (VT2) variant gene that was untypeable by the B subunit PCR and restriction fragment length polymorphism analysis (PCR-RFLP) method described by Tyler et al. (S. D. Tyler, W. M. Johnson, H. Lior, G. Wang, and K. R. Rozee, J. Clin. Microbiol. 29:1339-1343, 1991) was determined and compared with published sequences. It was highly homologous to two recently reported VT2 variant sequences. The PCR-RFLP method described by Tyler et al. was extended to include these new sequences. New VT2 variants were identified in 65 of 359 VT-producing Escherichia coli (VTEC) with newly designed primers (VT2-cm and VT2-f) and were characterized as well by restriction analysis of the amplification products obtained with another VT2-specific primer pair (VT2-e and VT2-f). The VT genes harbored by 64 of these isolates proved to be untypeable by Tyler's PCR-RFLP method because no amplification was obtained with the primers used with this method (VT2-c and VT2-d). The last isolate harbored the new variant gene in addition to VT2vh-a. None of the isolates harboring these new toxin genes belonged to serogroups O157, O26, O103, O111, and O145. All 65 isolates were negative for the eaeA gene and were significantly less frequently enterohemolytic or positive for the enterohemorrhagic E. coli (EHEC) virulence plasmid than non-O157 VTEC isolates harboring other VT2 genes. They were also less frequently isolated from patients with EHEC-associated symptoms. The extended PCR-RFLP typing method is a useful tool to identify less-virulent VTEC isolates and for VT genotyping in epidemiological studies with non-O157 strains.
Asunto(s)
Toxinas Bacterianas/genética , Escherichia coli/genética , Genes Bacterianos , Variación Genética , Animales , Toxinas Bacterianas/química , Técnicas de Tipificación Bacteriana , Secuencia de Bases , Cartilla de ADN/genética , Escherichia coli/aislamiento & purificación , Escherichia coli/patogenicidad , Infecciones por Escherichia coli/microbiología , Genotipo , Humanos , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Polimorfismo de Longitud del Fragmento de Restricción , Conformación Proteica , Homología de Secuencia de Ácido Nucleico , Toxina Shiga II , Virulencia/genéticaRESUMEN
PCR for verocytotoxin-producing Escherichia coli (VTEC) was positive in 4.6% of 2,440 raw meat samples; only beef, sheep, and venison samples were positive. None of the isolated VTEC strains belonged to serogroup O157. Additional virulence factors were detected in only a minority of strains, suggesting that most of these meat VTEC isolates are not pathogenic.
Asunto(s)
Toxinas Bacterianas/biosíntesis , Escherichia coli/patogenicidad , Carne/microbiología , Animales , Toxinas Bacterianas/genética , Bovinos , Ovinos , Toxina Shiga I , VirulenciaRESUMEN
A cDNA clone was isolated for a fourth pma gene encoding a putative plasma membrane H(+)-ATPase of Nicotiana plumbaginifolia. The sequence of the predicted 952 residue PMA4 polypeptide was compared with those of other known plant PMAs, revealing a higher identity with the Arabidopsis thaliana proteins (86-89%) than with the other three N. plumbaginifolia PMA proteins (80-82%). This supports the view that there are two pma subfamilies which probably arose from a gene duplication predating the separation of the Dilleniidae and Asteridae plant subclasses. Measured pma4 transcript levels indicate that pma4 is similarly expressed in root, stem, leaf, and flower tissues, contrary to the pmal-3 subfamily whose members displayed differential expression according to the organ.
Asunto(s)
Genes de Plantas , Familia de Multigenes , Nicotiana/genética , Plantas Tóxicas , ATPasas de Translocación de Protón/genética , Secuencia de Aminoácidos , Secuencia de Bases , Southern Blotting , Membrana Celular/enzimología , ADN , Datos de Secuencia Molecular , Filogenia , ATPasas de Translocación de Protón/clasificación , Nicotiana/enzimología , Transcripción GenéticaRESUMEN
During an 18-month period all stools submitted to a microbiology laboratory in Belgium for culture were screened for Verocytotoxin-producing Escherichia coli (VTEC) serotype O157. In the stool samples from 3940 patients, eight (0.2%) VTEC O157 strains were isolated, seven of which were O157:H7. Additional screening for other serotypes of VTEC in 332 selected stool samples yielded four more strains (serotypes O2:K1:H6, O111:H-, O117:K1:H7 and O"C70/86":H-). The 0.3% isolation rate for all VTEC was comparable to that for Shigella spp. Eight children under 30 months and two adults suffered from uncomplicated gastroenteritis. A 5-month-old child and a 41-year-old woman presented with hemolytic uremic syndrome a few days after onset of a diarrheal episode.