CHARACTERIZATION OF PHI-393-A2, A BACTERIOPHAGE THAT INFECTS LACTOBACILLUS-CASEI

Bacteriophage phi 393-A2, isolated from an artisanal cheese whey sample, is a temperate phage able to generate stable lysogens through integration of its DNA into the bacterial genome. One-step growth kinetics of its lytic development revealed eclipse and latent periods of 100 and 140 min. respectively, with a burst size of about 200 p.f.u. per infected cell. phi 393-A2 virions have an isometric head and a long, non-contractile tail terminating in a baseplate. The capsid is composed of two major and at least nine minor structural polypeptides. The phage genome consists of a double-stranded DNA molecule of 44 kbp bearing 3'-protruding cohesive ends. A physical map of the phage DNA has been constructed for six restriction enzymes. The whole phi 393A2 genome has been cloned in Escherichia coli using plasmid- and phage-derived cloning vectors.