Étude comparative des DNA de phages 2C, SP 8*, SP 82, φe, SP 01 et SP 50

Abstract

The following Bacillus subtilis phages: SP8*, SP82, @e, SPO1,2C and SP50, were studied and compared for morphological characteristics as well as for physico-chemical properties of their DNA. All the determinations were efiected under identical conditions for the six different phages. The aspect and variety of plaques formed by them with susceptible strain B. subtilis 168-2 (as indicator host), on Difco nutrient agar plates, are slightly different from phage to phage, but do not allow differenciation.As shown by electron microscopy measurements, the five phages SP8*, SP82, SPO1, @e, and 2C are morphologically identical and easily distinguishable from SP50, but not from each other.As for the physico-chemical properties of their DNA, the first five phages are clearly different from SP50 DNA which was taken as a reference: (a) their analytical base composition is consistently the same, all of them containing hydroxymethyluracil instead of thymine in their DNA, and the analyzed percentage guanine plus cytosine is 390/,, as compared to 41.6O/, for SP50 DNA which has no unusual bases; (b) sedimentation coefficients for all the DNA (including SP50 DNA) are about 51 S, a t a concentration of 20 p.g/ml ( $ 2 0 ,~) ; (c) the melting point in 0.15 M NaCI, 0.015M Na citrate is 77.5", without any significant variation among the first group (as compared to 87.3", for SPBO, which is approximately the same as the host Bacillus subtilis 168-2); (d) in a cesium chloride gradient, the buoyant densities of the native DNA of the first group are all 1.742 g/cm3. Since the complementary strands differ in average base composition, two bands of buoyant density 1.752 and 1.762 g/cm3 are obtained following denaturation; (e) all denatured DNA become associated with polyriboguanylic acid [poly(G)], which is preferentially bound to the heavy component, although a slight binding to the light component also occured.Preparative centrifugation in CsCl density gradients in the presence of poly G results in good separation of the two components; (f) the extent of homologous base sequence among the six phages has been determined by DNA/DNA hybridization : hybridization of 2C DNA, SPOl DNA and SP82 DNA with 2C DNA is experimentally identical and assumed to represent 100°/, homology. However for SP8 DNA/2C DNA and @e DNA/2C DNA, the percentage is lower, amounting t o 92O/, and 83O/,, respectively. With SP50 and B. subtilis DNA it is only 7O/,.On the whole, there are no apparent properties, peculiar to one of the 2C, SP8*, SP82, @e, and SPOl phages, allowing its differentiation from the others, whereas SP50 is morphologically distinct, particularly by the length of its tail. It also differs by diverse physical and biological properties. All the common characteristics possessed by the first group of phages, particularly the high extent of DNA/DNA hybridization among them, and the fact that the phages and their DNA are serologically related, demonstrate their close relationship.Parmi les bacteriophages de Bacillus subtilis, certains ont la particularit6 ...

Bacteriophage resistance in Bacillus subtilis 168, W23, and interstrain transformants

“…Therefore, by comparing the plating efficiency of these three bacteriophages, one can obtain a good indication of the type of mutation responsible for the loss of glucosylated cell wall teichoic acid. Similarly, these bacterial cell wall mutants can be used to distinguish these three closely related bacteriophages (9,19).…”

Digestion of highly modified bacteriophage DNA by restriction endonucleases

“…PBS1 DNA with 36 mole % U (13) and SPO1 DNA with 31 mole % hm5U (28) were cleaved by most of the examined restriction endonucleases but often more slowly than a normal DNA substrate was (Tables 1 & 2). A number of the enzymes tested did not detectably cleave these DNAs or cleaved them in an obviously incomplete manner especially in the case of enzymes with recognition sites that contained five or six base pairs (Tables 1 & 2).…”

Genes and Regulatory Sites of the “Host-Takeover Module” in the Terminal Redundancy ofBacillus subtilisBacteriophage SPO1

“…Most sequencing of PCR products and genomic DNA was done at the Molecular Genetics Core Facility of the University of Texas±Houston Medical School, using a PE/ABI Prism 377 DNA sequencer and an ABI Prism dye termination kit. Twenty-five to 27 base primers were needed to give the same quality sequences from SPO1 genomic DNA as those obtained with 20 to 22 base primers and thymine-containing templates, presumably because the presence of hmUra reduces the T m by about 10°C (Marmur and Doty, 1962;Okubo et al, 1964;Truffaut et al 1970). Sequencing with PCR product templates always used the complete product of the PCR reaction, and the sequences determined showed no higher proportion of ambiguity than those from other templates.…”