Denaturation maps of Bacillus licheniformis phages LP52 and theta DNAs

Plasmid analysis and restriction fragment length polymorphisms of chromosomal DNA allow a distinction between Borrelia burgdorferi strains

We examined the relationships of the genomes of five strains of Borrelia burgdorferi isolated from ticks, two from North America, including the type strain B31, and three from Switzerland. We determined restriction fragment length polymorphisms by using eight cloned DNA fragments as hybridization probes to genomic Southern blots. Two divergent patterns were observed, represented by B31 and one Swiss strain on the one hand and the two other Swiss strains on the other. The second American strain resembled B31. One of the DNA probes allowed distinction between the closely related strains within a group. The close resemblance of one Swiss strain to the North American strains suggests the possibility of their European origin. All five strains carried a circular plasmid of about 29 kb, and three contained an additional species of about 9 kb, both of which exhibited homology between the strains. The profiles of linear plasmids revealing species of 5.1 kb to 58 kb reflected the polymorphisms of chromosomal DNAs. Linear plasmids of similar size shared DNA sequence homology. Some of the smaller plasmids tended to become lost during cultivation.

Correlation of physical maps and some genetic functions in the genomes of the kappa-theta phage family of Bacillus licheniformis

Natural recombinant genomes between several, phenotypically distinct forms of phages kappa and theta were isolated and characterized by DNA restriction fragment mapping and electron microscopic heteroduplex analysis. The phenotypes of the recombinants were correlated with the physical maps of the genomes, and several genetic functions were therefore defined and mapped. All genes necessary for the assembly of infectious virus particles map in a contiguous tract of DNA comprising about 20 kb, or nearly one third of the genome length. No DNA homology occurs within these domains of the two genomes, so that homologous recombination does not take place here and phenotypic mixing of the phages is eo ipso excluded. Other regions of heterology contain regulatory genes responsible for the lytic or temperature character of the phages, and for exclusion of phage kappa by 9.