coli S17-1, and the obtained strains were used in bi-parental mating assays. In this case, transconjugants containing pMS32-DIY and pMAO-MS (but not pMAO-RK) were obtained for (1) A. tumefaciens LBA1010 (transfer frequency 3.2 × 10−6 and 2.8 × 10−8, respectively) and P. aminovorans JCM 7685 (transfer frequency 2.3 × 10−7 and 3.4 × 10−6, respectively) – both plasmids transferred, (2) R. etli CE3 (transfer of pMS32-DIY; frequency 1.4 × 10−4), and (3) Brevundimonas sp. GSK2126458 solubility dmso LM18R (transfer of pMAO-MS; 7.5 × 10−7). In summary, the aforementioned results provide evidence that the replication systems of pIGMS31 and pIGMS32

are active only in Gammaproteobacteria, but the mobilization systems of these plasmids function in a wider range of hosts. In this study, three plasmids (pIGMS31, pIGMS32, and pIGRK) harbored Obeticholic Acid in vitro by a pathogenic strain of K. pneumoniae 287-w have been fully sequenced and functionally characterized. These analyses revealed that pIGMS31, pIGMS32, and pIGRK contain different systems for mobilization for conjugal transfer, which are compatible with the helper transfer system of RK2. An intriguing observation was the transfer (at low frequency) of a Kmr derivative of plasmid pIGRK, whose MOB system was not predicted by classical comparative sequence analysis. pIGRK is a small cryptic plasmid, which,

besides the rep gene, carries Orotidine 5′-phosphate decarboxylase only an ORF encoding a protein with similarity

to phage-related integrases. The results of this study strongly suggest that pIGRK contains a true mobilization system, because transfer of this plasmid was dependent on the presence of (1) the helper system of plasmid RK2, (2) an intact int gene, and (3) a short DNA region placed upstream of the int gene (putative oriT). These observations indicate that the MOB of pIGRK is composed of both a cis-required sequence and a trans-acting protein, which is a typical structure in other well-defined mobilization systems. However, the predicted MOB of pIGRK does not share any sequence similarity with the MOBs of other plasmids. Although plasmids encoding phage-related integrases have been described previously (e.g. Werbowy et al., 2009; Zhang & Gu, 2009), to our knowledge, this is the first study to provide evidence that such a protein may participate in mobilization for conjugal transfer. Further studies are required to confirm these observations by more detailed molecular analyses. It was also demonstrated that pIGMS31, pIGMS32, and pIGRK are NHR plasmids, which can be maintained solely in closely related species of Gammaproteobacteria, but not in Alphaproteobacteria. In contrast, the MOBs of pIGMS31 and pIGMS32 enabled the conjugal transfer of heterogeneous replicons into several Alphaproteobacteria hosts (from the genera Agrobacterium, Brevundimonas, Paracoccus, and Rhizobium).