Genome Homology and Host Range of Some SPbeta-related Bacteriophages of Bacillus Subtilis and Bacillus amyloliquefaciens

Abstract

SUMMARYTemperate Bacillus subtilis bacteriophages SBfl, $3T and SPR and B. amyloliquefaciens phage H2 were compared with respect to DNA-DNA homology by Southern blot analysis to each other and to members of the genus Bacillus. The results show that H2 is a distantly related member of the group III B. subtilis phages. Detectable homology to group III phages could be found in the DNA of several other Bacillus species, including B. natto and B. amyloliquefaciens, demonstrating the widespread occurrence of this group of phages. The host ranges for the phages SPfl, SPR and H2 were determined by adsorption efficiency and by the ability of erythromycin resistance-and chloramphenicol resistance-transducing phages to convert susceptible host strains. Of the three phages examined, only H2 was capable of infecting B. amyloliquefaciens. Based on these results we propose that group III phages should be divided into three subgroups: SPfl, $3T, Rhol 1, IG1, IG3 and Z (subgroup 1), SPR (subgroup 2) and H2 (subgroup 3).

The life cycle of SPβ and related phages

“…Reduced adsorption strongly impacts plaque formation and lysis of the host culture, mainly because the surrounding host cells grow faster than the phages can infect them [ 79 ]. This assumption is supported by transduction experiments showing the ability of SPβ to inject DNA into strain IGCgll4 [ 39 ]. These results imply a secondary attachment site for SPβ to which the phage adsorbs poorly.…”

“…SPβ-related phages fall into three subgroups [ 39 , 40 ]. Phages IG1, IG3, IG4, ρ11, and φ3T are particularly closely related to SPβ, as SPβ antiserum cross-reacts with all of these phages [ 33 , 39 ]. SPR belongs to the second subgroup.…”

“…Phage H2 represents a third subgroup [ 37 , 38 ]. It has less genome sequence similarity to other SPβ-like phages and a specific antiserum activity [ 39 ]. Three recent isolates, Goe11 [MT601272.1], Goe12 [MT601273.1], and Goe13 [MT601274.1], have been sequenced.…”

High defense system expression broadens protection range at the cost of increased autoimmunity

“…At native expression levels, we found that spbK strongly protects against phages SPβ and SPR with observed ~5 and ~4 orders of magnitude reduction in phage titer respectively, and no inhibition of bacterial growth (Fig 1B-G). Apart from these phages, which both belong to the SPβ-like family [15][16][17] , natively expressed spbK offered only weak protection against phage 29 (a 10-fold reduction in phage production that did not prevent bacterial population collapse). Increasing expression led to protection against some additional phages but not others.…”