A broad-host-range vector of incompatibility group Q can work as a plasmid vector in Neisseria meningitidis:: a new genetical tool

Plasmid pHT128, a derivative of the broad-host-range lncQ vector pGSS33, was successfully introduced into Neisseria meningitidis. Under optimal conditions, pHT128 was transferred from Escherichia coli to N. meningitidis by triparental conjugation at a frequency of 10(-5)-10(-6). The copy number of pHT128 in N. meningitidis was almost the same as in E. coli, in which the copy number of lncQ plasmids per chromosome is estimated to be 10. pHT128 was maintained as an episome in N. meningitidis in the presence of chloramphenicol, a marker of the plasmid. It was also shown that an opc or pilE1 gene cloned on pHT128 could be expressed in N. meningitidis under control of the tac promoter and could complement a mutation of opc or pilE1, respectively. In addition, the conjugational introduction of pHT128 into N. meningitides was demonstrated to be independent of natural transformation competence. All the results indicate that pHT128 is a useful vector for N. meningitidis as a new genetical tool.