Characterization of wild lambdoid bacteriophages: Detection of a wide distribution of phage immunity groups and identification of a Nus-dependent, nonlambdoid phage group

Temperate phages were isolated from fresh human fecal samples. Lambdoid pha ges were screened for growth on Nus+ but not Nus- bacteria. Approximately 1 00 independent lysogens of Nus-dependent phages were constructed and tested for immunity to superinfection by the same Nus-dependent phages. This iden tified 20 different phage immunity groups, 18 of which belonged to the lamb doid phage family. The DNA from the majority of these phages hybridized wit h a lambda DNA probe, and similar to 50% were recognized by anti-lambda ant ibodies. Furthermore most were inducible by UV light. Eleven phage recombin ants with different immunity were obtained when a phage from each group was coinfected with lambda or its derivative lambda BLK20. We also; identified another immunity group with 48 members. None of these hybridized with eith er lambda or phi 80 DNA probes nor were they recognized by anti-lambda seru m. Most were not induced by UV light treatment, and no recombinants were ob tained when crossed with either lambda or lambda BLK20. Consequently, this group of Nus-dependent phages represent a new nonlambdoid phage family. (C) 1999 Academic Press.