NOTES Integration and Distribution of Lactobacillus johnsonii Prophages

In Lactobacillus johnsonii strain NCC533, two prophages were integrated into tRNA genes and one was dis-rupted by integration. In a survey, the prophages were restricted to strains sharing an essentially identical restriction pattern. Microarray analysis showed that the prophage DNA represents about 50 % of the NCC533 strain-specific DNA. In many bacteria, genome sequencing identified prophages as a prominent part of the laterally acquired DNA. About two-thirds of the sequenced -proteobacteria and low-GC-content gram-positive bacteria contained one—many, even multiple—prophage (9). Further observations suggested an important role of prophages for bacterial genomes. Many pro-phages from bacterial pathogens encoded important virulence factors (4). In several pathogenic bacteria, sequencing of mul-tiple strains identified prophages as a major contributor to the strain-specific DNA (1, 16). Much less is known about the role of prophages in the genomes from nonpathogenic bacteria