Characterization of a lytic Lactobacillus plantarum bacteriophage and molecular cloning of a lysin gene in Escherichia coli

Bacteriophage SC921, which can infect Lactobacillus plantarum specifically, was isolated from a fermented vegetable source, Kimchi. This phage is acti ve against six of II strains of L. plantarum tested as hosts. Morphological ly, it has an isometric head (60 nm in diameter) and a non-contractile tail (260 nm long and 9-11 nm wide), indicating that it belongs to Bradley's gr oup B or the Siphovirodae family according to the International Committee o n Taxonomy of Viruses (ICTV). The bouyant density was 1.58 g/cm(3). SDS-PAG E experimentation indicated that the phage particle contains two major stru ctural proteins and several minor proteins. The genome was a double strande d linear DNA molecule with cohesive ends and 66.5 kb long by mapping genomi c DNA digested with the restriction endonucleases: KpnI, SmaI, and XbaI. Th e [G + C] content of the phage DNA is 39.4%. For this lysin gene study, 9.4 kb of KpnI-digested DNA fragment was cloned into pUC19 and expressed in Es cherichia coli. The KpnI fragment was considered as the genetic element res ponsible for the lysis gene of L. plantarum bacteriophage. The cloned fragm ent in pUC19 was hybridized to a 9.4-kb fragment generated by KpnI digestio n of SC 921 as a probe. This confirmed that the fragment in pUC19 originate d from phage DNA. The lysin gene was near the middle of the phage genome. ( C) 2001 Elsevier Science R.V. All rights reserved.