Pervasive prophage recombination occurs during evolution of spore-forming Bacilli

Abstract

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Phages carry interbacterial weapons encoded by biosynthetic gene clusters

“…The next question to address is whether phages are more specific than bacteriocins they carry, or vice versa. From comparing the narrow host range of SPb 24 with reports on the anti-staphylococcal activity of sublancin, 56 it may appear that the phages are more specific. However, a systematic study addressing this fascinating evolutionary question still awaits.…”

“…The spsM gene encodes for a polysaccharide synthase. 39 Not all B. subtilis strains carry spsM, 24 and the lack of this SPb attachment gene would greatly reduce the frequency of SPb integration into the host chromosome (Figure 5A). This would effectively render the spsM mutant less competitively fit compared to the wild type upon SPb invasion.…”

“…Phages can encode virulence factors, 21,22 toxins, 23 and other compounds that are potentially valuable for the host. For instance, the SPb prophage present in some strains of Bacillus subtilis, which is a soil, plant, and gut bacterium, 24 encodes for the S-linked glycocin, sublancin. 25,26 The sublancin cluster (5 kb) contains a precursor peptide (SunA), posttranslational modification enzymes (SunS, BdbA, and BdbB), a self-immunity protein (SunI), and a transporter (SunT) that ensures the export of the bacteriocin into the extracellular space.…”

“…30 This prophage can be found in closely related but geographically dispersed B. subtilis isolates, and it always occupies the same position in the chromosome. 24 The contribution of sublancin to the ecological success of SPb remains an open question. It is not known whether other phages or prophages carry BGCs, or whether the products of such BGCs may share structural or functional features.…”

The life cycle of SPβ and related phages

“…These species are morphologically very similar and are mainly mesophiles and neutrophiles [ 23 ]. Members of this clade are frequently suitable hosts for phages that were initially isolated on B. subtilis , such as φ29 [ 24 , 25 ], SP-15 [ 26 ], or SPO1 [ 27 ], and for diverse SPβ-related phages, as recent bioinformatic analysis has demonstrated [ 28 ].…”