The comQXPA locus of Bacillus subtilis encodes a quorum sensing (QS) system typical of Gram positive bacteria. It encodes four proteins, the ComQ isoprenyl transferase, the ComX pre-peptide signal, the ComP histidine kinase, and the ComA response regulator. These are encoded by four adjacent genes all situated on the same chromosome strand. Here we present results of a comprehensive census of comQXPA-like gene arrangements in 2620 complete and 6970 draft prokaryotic genomes (sequenced by the end of 2013). After manually checking the data for false-positive and false-negative hits, we found 39 novel com-like predictions. The census data show that in addition to B. subtilis and close relatives, 20 comQXPA-like loci are predicted to occur outside the B. subtilis clade. These include some species of Clostridiales order, but none outside the phylum Firmicutes. Characteristic gene-overlap patterns were observed in comQXPA loci, which were different for the B. subtilis-like and non-B. subtilis-like clades. Pronounced sequence variability associated with the ComX peptide in B. subtilis clade is evident also in the non-B. subtilis clade suggesting grossly similar evolutionary constraints in the underlying quorum sensing systems.

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Therapeutic strategies to increase the effectiveness of cough Cough is a natural reflex that protects respiratory airways against infections or mucus retention. Cough maintains an adequate cleaning of the airways and isa tos en un reflejo natural de protección de la vía aérea que cumple con dos funciones fundamentales: mantener las vías respiratorias libres de elementos extraños y expulsar el exceso de secreciones producidas en condiciones reológicas anormales 1 . Si bien la tos se define como un reflejo, puede ser desencadenada de forma voluntaria por el paciente o provocada por un profesional constituyendo una herramienta importante dentro del arsenal terapéutico destinado a mantener un adecuado drenaje de secreciones. Es utilizada en una gran variedad de patologías, principalmente en adultos que colaboren pero, en circunstancias específicas, puede ser desencadenada de forma involuntaria en lactantes, pacientes con daño neurológico o cualquier enfermo no colaborador 2 .El objetivo de este texto fue analizar los mecanismos fisiológicos de la tos, las herramientas para evaluar su eficacia y clasificar las distintas técnicas manuales e instrumentales que actualmente el terapeuta tiene a su disposición para procurar el mayor beneficio al paciente. I. La tosClásicamente, la literatura describe tres fases en la ejecución de la tos: fase inspiratoria, que consiste en inspirar el mayor volumen de aire posible; fase compresiva, que comprende el cierre de la glotis y la presurización del sistema respiratorio esencialmente por la contracción de la musculatura