Distribution of bacteriophage phi 3T homologous deoxyribonucleic acid sequences in Bacillus subtilis 168, related bacteriophages, and other Bacillus species

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Abstract
The B. subtilis 168 chromosome shares extensive homology with the genome of bacteriophage .vphi.3T. At least 3 different regions of the bacterial genome hybridized to RNA complementary to .vphi.3T DNA. The thymidylate synthetase gene, thyA, of B. subtilis and the sequences adjacent to it were homologous to the region in the .vphi.3T DNA containing the phage-encoded thymidylate synthetase gene, thyP3. SP.beta., a temperate bacteriophage known to be integrated into the B. subtilis 168 chromosome, was closely related to .vphi.3T. Other regions of the bacterial genome also hybridized to the .vphi.3T probe. The nature and location of these sequences in the bacterial and phage chromosomes were not identified. These sequences were not homologous to either the thyP3 gene or the DNA surrounding the thyP3 gene. The chromosomes of other Bacillus spp. were also screened for the presence of .vphi.3T homologous sequences, and the thyP3 gene was localized in the linear genomes of phages .vphi.3T and .rho.11 by heteroduplex mapping. The presence of sequences of phage origin in the B. subtilis 168 chromosome might contribute to the restructuring and evolution of the viral and bacterial DNA.