Buenos días! pasamos para comunicarles que retomaremos los seminarios departamentales. El próximo miércoles tendremos a la Dra. Sofia Castell como oradora, quien realizó un posdoctorado en nuestro departamento, en el laboratorio de la Dra. Mariela Monti, y actualmente se encuentra trabajando en el CIBICI. El seminario se llevará a cabo en el auditorio del EN (primer piso), el miércoles 23 a las 13:30 hs. Enviamos un resumen de lo que será su charla. Los esperamos!! Comisión de seminarios Título: *Low fidelity DNA polymerase IV accelerates genome evolution of Pseudomonas aeruginosa* Translesion synthesis DNA polymerases are crucial for bypassing DNA lesion and facilitating various cellular processes. Despite extensive research, the mutagenic effects of these error-prone enzymes on genomes are still not fully understood. In this study, we examined the genomic instability caused by the specialized Pol IV polymerase in the bacterial pathogen Pseudomonas aeruginosa. We found that the primary mechanism of Pol IV mutagenesis involves the erroneous incorporation of oxidized guanine nucleotides opposite to a template adenine. This activity led to a distinctive mutational signature, characterized by A to C transversions occurring preferentially in AT sites flanked by a 5'G and/or 3'C. Furthermore, Pol IV exhibited a preference for targeting specific chromosomal locations near the replication termination region and the rRNA-encoding operons. Several genes associated with virulence, motility, antibiotic resistance and chemotaxis in P. aeruginosa are located in these difficult-to-replicate regions, making them hotspots for Pol IV-mutagenesis. Notably, half of the mutation events catalyzed by Pol IV effectively impaired gene function. This can be attributed to the strong bias of Pol IV for mutating specific codons that contain its preferred sequence contexts, leading to substitutions primarily to the unreactive Ala and Gly residues. Remarkably, all the mutation signatures identified for Pol IV were also present in genomes from clinical isolates of P. aeruginosa, providing compelling evidence for the involvement of this low-fidelity DNA polymerase in genetic diversification during pathogen adaptation. -- *Dra. Yohana Camila Garay* Becaria Posdoctoral de CONICET Dpto. Química Biológica Ranwel Caputto-CIQUIBIC Facultad de Ciencias Químicas Universidad Nacional de Córdoba Haya de la Torre y Medina Allende Ciudad Universitaria X5000HUA, Córdoba, Argentina Tel: (0054) 0351-5353855 (3419)