KPNAI, A NEW-TYPE-I RESTRICTION-MODIFICATION SYSTEM IN KLEBSIELLA-PNEUMONIAE

The KpnAI restriction-modification (R-M) system has been identified in Klebsiella pneumoniae strain M5a1. The restriction gene of KpnAI was first cloned into pBR322 using an r(-)m(+) M5a1 derivative and phage S BS for screening. Subsequently, an adjacent DNA fragment showing modif ication activity was cloned into pUC19. A total of 7.2 kb DNA sequenci ng data revealed three open reading frames, corresponding to hsdR, hsd M and hsdS genes of type I R-M systems. The predicted hsdR, hsdM and h sdS-coded peptides shared 95%, 98% and 44% identity, respectively, wit h the corresponding peptides of the recently identified StySBLI system , a prototype of the type ID family. This high homology suggests that KpnAI is also a member of the type ID family. The KpnAI system seems t o be the first type I system identified in Klebsiella species. (C) 199 7 Academic Press Limited.