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

Abstract

Temperate phages were isolated from fresh human fecal samples. Lambdoid phages were screened for growth on Nus+ but not Nus- bacteria. Approximately 100 independent lysogens of Nus-dependent phages were constructed and tested for immunity to superinfection by the same Nus-dependent phages. This identified 20 different phage immunity groups, 18 of which belonged to the lambdoid phage family. The DNA from the majority of these phages hybridized with a λ DNA probe, and ~50% were recognized by anti-λ antibodies. Furthermore most were inducible by UV light. Eleven phage recombinants with different immunity were obtained when a phage from each group was coinfected with λ or its derivative λBLK20. We also identified another immunity group with 48 members. None of these hybridized with either λ or Φ80 DNA probes nor were they recognized by anti-λ serum. Most were not induced by UV light treatment, and no recombinants were obtained when crossed with either λ or λBLK20. Consequently, this group of Nus-dependent phages represent a new nonlambdoid phage family.