Possible Role of CHAD Proteins in Copper Resistance.

Conserved Histidine Alpha-helical Domain (CHAD) proteins attached to the surface of polyphosphate (PolyP) have been studied in some bacteria and one archaeon. However, the activity of CHAD proteins is unknown beyond their interaction with PolyP granules. By using bioinformatic analysis, we report that several species of the biomining acidophilic bacteria contain orthologs of CHAD proteins with high sequence identity. Furthermore, the gene coding for the CHAD protein is in the same genetic context of the enzyme polyphosphate kinase (PPK), which is in charge of PolyP synthesis. Particularly, the group of ppk and CHAD genes is highly conserved. Metallosphaera sedula and other acidophilic archaea used in biomining also contain CHAD proteins. These archaea show high levels of identity in genes coding for a cluster having the same organization. Amongst these genes are chad and ppx. In general, both biomining bacteria and archaea contain high PolyP levels and are highly resistant to heavy metals. Therefore, the presence of this conserved genetic organization suggests a high relevance for their metabolism. It has been formerly reported that a crystallized CHAD protein contains a copper-binding site. Based on this previous knowledge, in the present report, it was determined that all analyzed CHAD proteins are very conserved at their structural level. In addition, it was found that the lack of YgiF, an Escherichia coli CHAD-containing protein, decreases copper resistance in this bacterium. This phenotype was not only complemented by transforming E. coli with YgiF but also by expressing CHAD from Acidithiobacillus ferrooxidans in it. Interestingly, the strains in which the possible copper-binding sites were mutated were also more metal sensitive. Based on these results, we propose that CHAD proteins are involved in copper resistance in microorganisms. These findings are very interesting and may eventually improve biomining operations in the future.

Sessile Lifestyle Offers Protection against Copper Stress in Saccharolobus solfataricus.

Some archaea from the genus Sulfolobus are important for bioleaching of copper, where metal resistant microorganisms are required. Biofilm generation is one of the ways microorganisms cope with some stimuli in nature, including heavy metals. The response to external factors, particularly in the biofilm form of life, is still underexplored in archaea. To explore how model thermoacidophilic archaeon Saccharolobus solfataricus faces copper stress during this lifestyle, changes in biofilms were studied using crystal violet staining, confocal fluorescence microscopy, and qPCR approaches. It was found that biofilm formation reached a maximum at 0.5 mM Cu, before starting to decrease at higher metal concentrations. The morphology of biofilms at 0.5 mM Cu was observed to be different, displaying lower thickness, different sugar patterns, and higher amounts of cells compared to standard growing conditions. Furthermore, copA, which is responsive to intracellular Cu concentration, was downregulated in biofilm cells when compared with planktonic cells exposed to the same metal concentration. The latest results suggests that cells in biofilms are less exposed to Cu than those in planktonic culture. In a PolyP-deficient strain, Cu was not able to induce biofilm formation at 0.5 mM. In summary, the findings reported here suggest that the biofilm form of life confers S. solfataricus advantages to face stress caused by Cu.Biofilm formation remains a relatively unexplored topic in archaeal research. Therefore, this knowledge in model organisms such as S. solfataricus, and how they use it to face stress, could be of great importance to engineer organisms with improved capabilities to be applied in biotechnological processes, such as bioleaching of metals.

Perforación de guantes quirúrgicos en cesárea / Surgical gloves perforation in cesarean section

Con el objetivo de demostrar la frecuencia de perforación de guantes durante la operación cesárea, el miembro del equipo quirúrgico con mayor afección y la importancia del uso de doble guante durante la cirugía, se realizó un estudio prospectivo en 258 cesáreas realizadas en Tococirugía en el Nuevo Hospital Civil de Guadalajara, de septiembre 1993 a enero 1994. En las 258 cesáreas se utilizaron 1052 pares de guantes y se perforaron 118 (11.2 por ciento). Los guantes se perforaron en una sola ocación: 60.1 por ciento, en dos ocasiones: 26.2 por ciento, en tres ocasiones: 6.8 por ciento, en cuatro ocasiones: 1.7 por ciento y en cinco ocasiones: 5.2 por ciento. De los guantes rotos, en 74 por ciento se habían utilizado guantes simples y en 26 por ciento guantes dobles, únicamente se perforó el guante externo. De los integrantes del equipo quirúrgico, el más afectado con perforación de guantes fue el cirujano en 83 por ciento, el ayudante en 13.5 por ciento y el instrumentista en 3.5 por ciento. La mano más afectada fue la izquierda en 70.3 por ciento y la derecha en 29.7 por ciento. La perforación de guantes fue producida por aguja en 62.7 por ciento y por otros instrumentos en 37.3 por ciento. Se concluye que debido a la frecuencia de perforación de guantes transcirugía, es recomendable un mayor cuidado en la realización de los procedimientos quirúrgicos, así como el uso de guantes dobles para una mayor protección