Furthermore, Tn5251-like elements are highly capable of capturing other genetic elements carrying different antibiotic resistance determinants such as the mef(E) and erm genes conferring macrolide resistance, aadE, sat4 and aphA-3 conferring resistance to streptomycin, streptothricin and kanamycin, respectively. These features make these elements successful in disseminating multidrug resistance determinants among pathogenic bacterial species. In this context, characterization

of Tn5251 contributes to the understanding of the Alectinib nmr mechanisms of the spread of antibiotic resistance. This study was supported by the European Commission grants ANTIRESDEV HEALTH-F3-2009-241446 and by Universita’ degli Rapamycin Studi di Siena (PAR). “
“In a growth-restricting environment, mutants arise that are able to take over bacterial populations by a process known as adaptive mutation or stationary-phase mutation. This process is best studied in Escherichia coli. The genus Pseudomonas represents one of the largest groups of bacteria able to colonize multiple habitats and to adapt rapidly to new environments. The majority of bacteria including pseudomonads contain a different set of DNA polymerases and DNA repair enzymes

than those identified in E. coli. The aim of this review is to provide an overview of the results of studies of mutagenic processes in pseudomonads and to discuss these results in the light of the mechanisms of stationary-phase mutagenesis discovered in E. coli. Conditions for unrestricted growth are rarely met in natural environments, and therefore, most bacteria are in a state of slow or nongrowth, also called as a stationary phase (Poulsen et Glutathione peroxidase al., 1995; Bååth, 1998). Under stressful, growth-restricting conditions (e.g. nutrient starvation, during colonization of the host organism), microbial populations can rapidly evolve. Genetic changes in microbial populations can occur fast through the acquisition and incorporation of foreign DNA or through mutation. Genetic changes that result from the introduction of mutations

into DNA can arise by various mechanisms, including those caused by DNA damage, and via errors introduced during DNA replication. Replication errors can result from the failure of base selection, proofreading and DNA mismatch repair (MMR), which act sequentially to ensure the fidelity of replication (Schaaper, 1993). Mutagenesis occurring in growth-restricted cells is called adaptive mutation or stationary-phase mutation (Foster, 1999; Rosenberg, 2001). It has been suggested that a variety of environmental stresses induce genomic change in bacteria, generating occasional fitter mutants and potentially accelerating the evolution of bacterial populations (Metzgar & Wills, 2000; Rosenberg, 2001; Tenaillon et al., 2001; Bjedov et al., 2003; Kivisaar, 2003; Miller, 2005; Foster, 2007; Galhardo et al., 2007; Robleto et al., 2007; Baquero, 2009).