Instability of pneumococcus library in pHC79 and pACYC184

Abstract

S. pneumoniae (pneumococcus) gene cloning and library construction inE. coli multicopy plasmid has been hampered, in part, by instability problems. In this study, stability of pneumococcus gene library in cosmid vector and pACYC184 was examined. Pneumococcus library in the cosmid vector pHC79 was extremely unstable that most of the recombinant clones were degenerated rapidly. Only 2 out of 849 clones were stable and had appropriate insert size. Pneumococcus library in pACYC184 was also so unstable that the pneumococcal insert and/or part of the vector were deleted. However, the instability problems seemed to be resolved when transcription terminator plasmid was employed for pneumococcus library construction.