Structural organization and replication ability of pMyBK1 and derivatives. A. Plasmid constructs are described in Methods. Putative promoter and terminator of CDSA and CDSB are indicated for pMyBK1 only. Direct repeats (□) , inverted repeats (▸◂) and the GC-rich region (|||||) are indicated only for the pCM-C derivative. B, Bgl II; E, Eco RI; spi, Spiroplasma citri spiralin gene; tetM, tetracycline resistance gene from transposon Tn916, pBS, plasmid pBluescript. The signs on the right indicate the ability (+) and inability (−) to replicate in Mycoplasma yeatsii type strain GIH TS. * indicates a frameshift mutation in the cdsB sequence of pCM-K1ΔB. B. The replication ability of 4 pMyBK1 derivatives was evaluated in mollicute species belonging to the Spiroplasma phylogenetic group and shown to be initially plasmid-free: M. yeatsii #13156, M. putrefaciens KS1 TS, M. leachii PG50 TS, Mcc California kid TS, Mmc GM12, Mmm T1/44 and S. citri GII3. The signs on the right indicate the ability (+) and inability (−) to replicate in a given species. ND: not determined. A: plasmid integration in the Mmc chromosome. B: spiralin expression in Mcc was detected by immunoblot.