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00925njm 22002777a 4500 dc Nieto, Concha author Sadowy, Ewa author de la Campa, Adela G author Hryniewicz, Waleria author Espinosa, Manuel author 2010-06-23 Type II (proteic) chromosomal toxin-antitoxin systems (TAS) are widespread in Bacteria and Archaea but their precise function is known only for a limited number of them. Out of the many TAS described, the relBE family is one of the most abundant, being present in the three first sequenced strains of Streptococcus pneumoniae (D39, TIGR4 and R6). To address the function of the pneumococcal relBE2Spn TAS in the bacterial physiology, we have compared the response of the R6-relBE2Spn wild type strain with that of an isogenic derivative, Delta relB2Spn under different stress conditions such as carbon and amino acid starvation and antibiotic exposure. Differences on viability between the wild type and mutant strains were found only when treatment directly impaired protein synthesis. As a criterion for the permanence of this locus in a variety of clinical strains, we checked whether the relBE2Spn locus was conserved in around 100 pneumococcal strains, including clinical isolates and strains with known genomes. All strains, although having various types of polymorphisms at the vicinity of the TA region, contained a functional relBE2Spn locus and the type of its structure correlated with the multilocus sequence type. Functionality of this TAS was maintained even in cases where severe rearrangements around the relBE2Spn region were found. We conclude that even though the relBE2Spn TAS is not essential for pneumococcus, it may provide additional advantages to the bacteria for colonization and/or infection. PLoS One. 2010 Jun 23;5(6):e11289. 10.1371/journal.pone.0011289 1932-6203 1932-6203 PloS one 20585658 http://hdl.handle.net/20.500.12105/6865 The relBE2Spn toxin-antitoxin system of Streptococcus pneumoniae: role in antibiotic tolerance and functional conservation in clinical isolates