The replication locus of the theta-type SCP2 comprises repI and repII genes and an adjacent non-coding sequence to which RepI protein binds [7, 13]. pFP1 and pFP11 contain basic replication loci

of rep and Selleckchem MK 2206 iteron types (direct repeats and/or inverted repeats), to which Rep proteins bind [8]. Conjugal transfer of Streptomyces RC plasmid (e.g. pIJ101) needs a tra gene along with a clt (cis-acting locus of transfer) site [14]. Streptomyces tra genes encode a DNA translocase resembling the chromosomal DNA translocase FtsK of E. coli or SpoIIIE of B. subtilis[3], with double-stranded DNA probably entering the recipient [15]. The TraB of pSVH1 binds to the clt sequence as multimers on the mobilized plasmid and translocates unprocessed DNA at the hyphal tip to a recipient cell [16]. Conjugal transfer of Streptomyces theta-type plasmids (e.g. SCP2 and pZL12) requires a major tra gene and two adjacent genes [17, 18]. In contrast to most bacteria, Streptomyces

species often harbor linear plasmids [19, 20]. Unlike the terminal protein-capped linear replicons of adenoviruses that replicate by a mechanism of strand displacement [21], Streptomyces linear plasmids start replication from a centrally located ori locus [22] and replication Pritelivir proceeds bi-directionally toward the telomeres [23]. At least some Streptomyces linear plasmids (e.g. pSCL1) can propagate in circular mode when the telomeres are Doramapimod ic50 deleted [22], while some theta-type circular plasmids (e.g. SCP2 and pFP11) can also propagate in linear mode when the telomeres from a linear plasmid are attached [8]. Results Identification of a

widely distributed Streptomyces species Y27 and its indigenous plasmid pWTY27 among endophytic Streptomyces strains During the course of investigating naturally circular plasmids, we detected 27 plasmids among ~300 newly isolated actinomycete strains from plant samples of Gingko, Taxus and Artemisia annua L in China. Interestingly, 14 of them (Table 1) displayed similar sizes of ca.14-kb DNA bands on agarose gel. These plasmids were Obatoclax Mesylate (GX15-070) digested with NcoI and all showed five bands (~8, 2.2, 1.7, 1.3 and 1 kb) on gel electrophoresis (Additional file 1: Figure S1), suggesting that they were an identical plasmid (designated pWTY27). Table 1 Strains and plasmids used in this study Strain and plasmid Genotype or description Source or reference Strains     Streptomyces strains (Y27, Y32, Y33, Y34, Y41, Y42 and G2-1) Isolated from Gingko harboring pWTY27 This work Streptomyces strains(W15, W24, W37 and W41) Isolated from Artemisia annua L harboring pWTY27 This work Streptomyces strains (Z20, Z54 and Z70) Isolated from Taxus harboring pWTY27 This work S. lividans ZX7 pro-2 str-6 rec-46 dnd SLP2- SLP3- 34 S.