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Characterization and genome sequencing of two Propionibacterium acnes phages displaying pseudolysogeny.

Lood R, Collin M - BMC Genomics (2011)

Bottom Line: The genomes of PAD20 and PAS50 are 29,074 and 29,017 bp, respectively, compared with the 29,739 bp of PA6.Some deletions and insertions in the genomes have occurred, resulting in lack of genes, frame shifts, and possible regulatory differences.No obvious virulence factor gene candidates were found.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Clinical Sciences, Division of Infection Medicine, Lund University, Sweden. rolf.lood@med.lu.se

ABSTRACT

Background: Propionibacterium acnes is a Gram positive rod inhabiting the human skin that also infects orthopaedic implants and is associated with acne vulgaris. Previously, one lytic bacteriophage, PA6, from P. acnes has been sequenced and partially characterized. We recently isolated several inducible phages from P. acnes classified as Siphoviruses based on morphology and partial genome sequencing.

Results: In this study we sequenced the inducible P. acnes phages PAD20 and PAS50, isolated from deep infection and from skin, respectively. The genomes of PAD20 and PAS50 are 29,074 and 29,017 bp, respectively, compared with the 29,739 bp of PA6. The phage genomes have 87.3-88.7% nucleotide sequence identity. The genes are divided into clusters with different levels of similarity between the phages. PAD20 and PAS50 share four genes encoding identical amino acid sequences. Some deletions and insertions in the genomes have occurred, resulting in lack of genes, frame shifts, and possible regulatory differences. No obvious virulence factor gene candidates were found. The phages are inducible, but bacteria can be cured of phages by serial colony isolations and lose their phages during stationary phase, but are still sensitive to new phage infections. Construction of a phylogenetic tree based on more than 459 phage genomes, suggested that P. acnes phages represent a new lineage of Siphoviruses.

Conclusions: The investigated P. acnes Siphovirus genomes share a high degree of homology to other P. acnes phages sequenced, but not to genomes of other phages isolated from Propionibacteria. The phage genomes are not integrated in the bacterial genome, but instead, most likely have a pseudolysogenic life cycle.

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Growth curve of the P. acnes isolates used. P. acnes isolates AD20 (triangles) and AS50 (circles) were cultured in BHI, and OD600 was measured every 12 hours. The figure is a representative growth curve out of three independent experiments.
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Figure 3: Growth curve of the P. acnes isolates used. P. acnes isolates AD20 (triangles) and AS50 (circles) were cultured in BHI, and OD600 was measured every 12 hours. The figure is a representative growth curve out of three independent experiments.

Mentions: To further investigate if P. acnes might harbour pseudolysogenic phages, single colonies from the P. acnes isolates AD20 and AS50 were inoculated into BHI broth and different parameters such as OD600 and pfu were measured two times a day (see Figure 3 and Table 4). No free infectious phages were detected at any time point, indicating that if any phages were spontaneously induced, their number have not exceeded the detection limit of 100 pfu/ml. However, at time points corresponding to mid-log phase and late-log phase, both AD20 and AS50 had 10-60% colonies harbouring phage DNA, as judged by PCR amplification of the major head gene (see Table 4). However, this carriage of phages is lost during the stationary growth phase, thus indicating that the phage DNA is not being replicated at this time point. Furthermore, the cells at the various time points were sensitive to PAD20 and PAS50 infection, indicating that the loss of phages were not due to the development of resistance (data not shown). This implies that the phages are not strictly lytic, neither strictly lysogenic.


Characterization and genome sequencing of two Propionibacterium acnes phages displaying pseudolysogeny.

Lood R, Collin M - BMC Genomics (2011)

Growth curve of the P. acnes isolates used. P. acnes isolates AD20 (triangles) and AS50 (circles) were cultured in BHI, and OD600 was measured every 12 hours. The figure is a representative growth curve out of three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3094311&req=5

Figure 3: Growth curve of the P. acnes isolates used. P. acnes isolates AD20 (triangles) and AS50 (circles) were cultured in BHI, and OD600 was measured every 12 hours. The figure is a representative growth curve out of three independent experiments.
Mentions: To further investigate if P. acnes might harbour pseudolysogenic phages, single colonies from the P. acnes isolates AD20 and AS50 were inoculated into BHI broth and different parameters such as OD600 and pfu were measured two times a day (see Figure 3 and Table 4). No free infectious phages were detected at any time point, indicating that if any phages were spontaneously induced, their number have not exceeded the detection limit of 100 pfu/ml. However, at time points corresponding to mid-log phase and late-log phase, both AD20 and AS50 had 10-60% colonies harbouring phage DNA, as judged by PCR amplification of the major head gene (see Table 4). However, this carriage of phages is lost during the stationary growth phase, thus indicating that the phage DNA is not being replicated at this time point. Furthermore, the cells at the various time points were sensitive to PAD20 and PAS50 infection, indicating that the loss of phages were not due to the development of resistance (data not shown). This implies that the phages are not strictly lytic, neither strictly lysogenic.

Bottom Line: The genomes of PAD20 and PAS50 are 29,074 and 29,017 bp, respectively, compared with the 29,739 bp of PA6.Some deletions and insertions in the genomes have occurred, resulting in lack of genes, frame shifts, and possible regulatory differences.No obvious virulence factor gene candidates were found.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Clinical Sciences, Division of Infection Medicine, Lund University, Sweden. rolf.lood@med.lu.se

ABSTRACT

Background: Propionibacterium acnes is a Gram positive rod inhabiting the human skin that also infects orthopaedic implants and is associated with acne vulgaris. Previously, one lytic bacteriophage, PA6, from P. acnes has been sequenced and partially characterized. We recently isolated several inducible phages from P. acnes classified as Siphoviruses based on morphology and partial genome sequencing.

Results: In this study we sequenced the inducible P. acnes phages PAD20 and PAS50, isolated from deep infection and from skin, respectively. The genomes of PAD20 and PAS50 are 29,074 and 29,017 bp, respectively, compared with the 29,739 bp of PA6. The phage genomes have 87.3-88.7% nucleotide sequence identity. The genes are divided into clusters with different levels of similarity between the phages. PAD20 and PAS50 share four genes encoding identical amino acid sequences. Some deletions and insertions in the genomes have occurred, resulting in lack of genes, frame shifts, and possible regulatory differences. No obvious virulence factor gene candidates were found. The phages are inducible, but bacteria can be cured of phages by serial colony isolations and lose their phages during stationary phase, but are still sensitive to new phage infections. Construction of a phylogenetic tree based on more than 459 phage genomes, suggested that P. acnes phages represent a new lineage of Siphoviruses.

Conclusions: The investigated P. acnes Siphovirus genomes share a high degree of homology to other P. acnes phages sequenced, but not to genomes of other phages isolated from Propionibacteria. The phage genomes are not integrated in the bacterial genome, but instead, most likely have a pseudolysogenic life cycle.

Show MeSH
Related in: MedlinePlus