Abstract
BackgroundLytic bacteriophages that infect Campylobacter spp. have been utilized to develop therapeutic/decontamination techniques. However, the association of Campylobacter spp. and bacteriophages has been the focus of several strands of research aimed at understanding the complex relationships that have developed between predators and prey over evolutionary time. The activities of endogenous temperate bacteriophages have been used to evaluate genomic rearrangements and differential protein expression in host cells, and mechanisms of resistance to bacteriophage infection in campylobacters such as phase variation and CRISPR-mediated immunity.ResultsTemperate bacteriophage DA10 represents a novel excised and infective virus capable of replication in a restricted set of C. jejuni and C. coli hosts. Whole genome sequencing reveals that DA10 (35,379 bp) forms part of a novel group of temperate bacteriophages that have limited distribution among database host genome sequences. Analysis of potential host genomes reveals a robust response against DA10 and DA10-like bacteriophages is driven by CRISPR-mediated immunity with 75% of DA10 ORFs represented as ~ 30 bp spacer sequences in numerous Campylobacter Type II-C CRISPR arrays. Several DA10-like homologues have been identified in a small sub-set of C. jejuni and C. coli genome sequences (ranging from near complete integrated prophage sequences to fragments recognisable in the sequence read archive).ConclusionsA complete intact DA10-like prophage in C. jejuni CJ677CC520 provides evidence that the associations between host and DA10-like bacteriophages are long-standing in evolutionary timescales. Extensive nucleotide substitution and loss can be observed in the integrated DA10-like prophage of CJ677CC520 compared to other relatives as observed through pairwise genome comparisons. Examining factors that have limited the population expansion of the prophage, while others appear to have thrived and prospered (Mu-like, CJIE-like, and lytic Campylobacter bacteriophages) will assist in identifying the underlying evolutionary processes in the natural environment.
Highlights
Lytic bacteriophages that infect Campylobacter spp. have been utilized to develop therapeutic/ decontamination techniques
Genomic rearrangements mediated by the activity of Mu-like prophages (CJIE1 known as CMLP-1/CampMu-like phage 1) are recognized as major factors governing host resistance to phage predation [7]
Characterisation of bacteriophage DA10 Transmission electron microscopy confirmed the morphology of phage DA10 to feature a contractile tail with an icosahedral head (Fig. 1a and b) indicating phage DA10 is a myovirus
Summary
Lytic bacteriophages that infect Campylobacter spp. have been utilized to develop therapeutic/ decontamination techniques. The activities of endogenous temperate bacteriophages have been used to evaluate genomic rearrangements and differential protein expression in host cells, and mechanisms of resistance to bacteriophage infection in campylobacters such as phase variation and CRISPR-mediated immunity. As with many bacteria Campylobacter spp. are known to harbour prophage/prophage remnants, for example the C. jejuni integrative elements – CJIE, and Mu-like bacteriophage (phage) sequences [5,6,7]. Genomic rearrangements mediated by the activity of Mu-like prophages (CJIE1 known as CMLP-1/CampMu-like phage 1) are recognized as major factors governing host resistance to phage predation [7]. Whilst CJIE2 and CJIE4 possess hallmark features of prophage/prophage remnants, CJIE3 most likely arose following integration of a plasmid-like mobile element into the host chromosome [14]. It has been shown that CJIE1 and other relatives (CJIE4) have the potential to influence protein expression of their bacterial lysogens [16]
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