Evolutionary considerations of related Bacillus subtilis temperate phages φ105, ϱ14, ϱ10, and ϱ6 as revealed by heteroduplex analysis

• Published in: Virology (New York, N.Y.) Vol. 99; no. 1; pp. 57 - 65
• Main Authors: Rudinski, Mark S., Dean, Donald H.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1979
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/0042-6822(79)90036-9

The temperate Bacillus subtilis bacteriophages φ105, ϱ14, ϱ10, and ϱ6 have previously been shown to be 80% homologous by studies on serology, host range, immunity, and plating efficiency on resistant cells. Physical analysis by restriction endonuclease mapping of phage DNA has also demonstrated that restriction sites and comigrating fragments are largely conserved (90% homologous). Here we show by heteroduplex analysis, using φ105 DNA as a standard, that these phage genomes have extensive nucleic acid homology. Phage DNAs were hybridized to φ105 DNA at 50 and 30% formamide conditions. The ϱ14/φ105 hybrid at 50% formamide showed three consistent denaturation bubbles: A-14 at the left end, and B-14 and C-14 in the central region. These bubbles were also present at 30% formamide indicating extensive nonhomology. The ϱ10/φ105 hybrid exhibited a single bubble close to a hybrid terminus at 50% formamide but not at 30%. A single central bubble and one split end were seen in the ϱ6/φ105 hybrid. To orient the molecules, a known φ105 deletion mutant, DI:2C, was hybridized to ϱ14. The degree of homology determined by measurement of double-stranded areas for this group of phages is 80%. The heteroduplex data show that some regions of partial homology exist indicating that sequence divergence has occurred as accumulated base substitutions but also that complete divergence has occurred, possibly by inversion, in larger-sized units in the central and left ends of these phage genomes.