Ultrastructure of Bacillus licheniformis bacteriophage BLE and its DNA

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.

Denaturation maps of Bacillus licheniformis phages LP52 and theta DNAs

Employing electron microscopy (EM) of partially denatured DNAs of phages LP52 and theta, distinct denaturation maps were determined and correlated with published restriction and heteroduplex maps. The pattern of early melting regions is similar although the two phages share only 50% nucleotide sequence homology.

An electron microscopic heteroduplex study of the sequence relations between the bacteriophages LP52 and theta

The genomes of the phylogenetically related but morphologically distinct bacteriophages LP52 and theta (theta) were compared by electron microscopic heteroduplex analysis. The heteroduplex maps were aligned with known restriction maps. In the heteroduplices of LP52 DNA (63.8 kb) with the DNA of the lytic phage theta c (65.9 kb) the tracts of homologous DNA cover about 50% of the genome length and are interspaced by four large and ten smaller non-base-paired regions. The largest block of non-homologous DNA (18.9 kb), represents the right-hand end and there is an unmatched piece of DNA at the left-hand end as well. Most of the heterology is due to substitution resulting in the conservation of the total length of DNA; the three insertions/deletions amount to less than 3.2% of the genome length. Heteroduplices between the DNAs of phage LP52 and the temperate phage theta 1 (65.0 kb) resembled those of LP52:theta c except for the absence of minor loops. Heteroduplex theta c:theta 1 displayed about 9% heterology in seven separate loops which coincided with sections of diversity on the restriction maps; 4.8% of theta 1 DNA did not hybridize with either theta c or LP52 DNA.

Physical mapping of the genomes of lytic and temperate forms of phage theta

Restriction maps of genomes of the lytic form and diverse temperate mutants of phage theta of Bacillus licheniformis were constructed. Most temperate mutants produced fragmentation patterns identical to that of the parent lytic form, theta c: in other mutants the only detectable change in the map was the deletion of a Bg/II restriction endonuclease site at 46.5% genome length. In the genomes of two other temperate mutants, theta 1 and theta 2, the central part of the genome was replaced by a piece of DNA of equal length, but with a different distribution of restriction sites; the maps of the two mutants failed to reveal any similarity in the location of restriction sites in the inserted DNA. It seems that any alteration comprising the locus around the coordinate 46.5% of the theta c genome, brings about a transition from the lytic to temperate phenotype, indicating the position of a regulatory gene responsible for positive control of phage replication.

Degradation by Eco R1 endonuclease of DNA isolated from phages infecting Bacillus licheniformis and Bacillus thuringiensis

DNA was isolated from lytic phages of two strains, Bacillus licheniformis, a producer of bacitracin, and Bacillus thuringiensis forming protein paracrystals with pronounced insecticidal effects. Its sensitivity to Eco R1 restriction endonuclease was determined. It was the aim of the work to find out whether these phages could serve as vectors in the transfer and possible amplification of genes of the two important industrial species of bacilli. Approximate values of the molecular weight of DNA of the two phages were determined after degradation of the phage DNA by Eco R1, followed by comparison of electrophoretic mobility of individual fragments with that of the Eco R1-degraded DNA of phage lambdab2.