Abstract
BackgroundBurkholderia species exhibit enormous phenotypic diversity, ranging from the nonpathogenic, soil- and water-inhabiting Burkholderia thailandensis to the virulent, host-adapted mammalian pathogen B. mallei. Genomic diversity is evident within Burkholderia species as well. Individual isolates of Burkholderia pseudomallei and B. thailandensis, for example, carry a variety of strain-specific genomic islands (GIs), including putative pathogenicity and metabolic islands, prophage-like islands, and prophages. These GIs may provide some strains with a competitive advantage in the environment and/or in the host relative to other strains.ResultsHere we present the results of analysis of 37 prophages, putative prophages, and prophage-like elements from six different Burkholderia species. Five of these were spontaneously induced to form bacteriophage particles from B. pseudomallei and B. thailandensis strains and were isolated and fully sequenced; 24 were computationally predicted in sequenced Burkholderia genomes; and eight are previously characterized prophages or prophage-like elements. The results reveal numerous differences in both genome structure and gene content among elements derived from different species as well as from strains within species, due in part to the incorporation of additional DNA, or 'morons' into the prophage genomes. Implications for pathogenicity are also discussed. Lastly, RNAseq analysis of gene expression showed that many of the genes in ϕ1026b that appear to contribute to phage and lysogen fitness were expressed independently of the phage structural and replication genes.ConclusionsThis study provides the first estimate of the relative contribution of prophages to the vast phenotypic diversity found among the Burkholderiae.
Highlights
Burkholderia species exhibit enormous phenotypic diversity, ranging from the nonpathogenic, soiland water-inhabiting Burkholderia thailandensis to the virulent, host-adapted mammalian pathogen B. mallei
Specific details about each of these bacteriophages are provided below, representative images of each isolated bacteriphage are shown in Fig. 1A and other properties are described in Table 1A. j52237 B. pseudomallei Pasteur 52237 spontaneously produced a bacteriophage, designated j52237 that formed uniform, slightly turbid plaques on B. mallei ATCC 23344, suggesting that this strain produces only one bacteriophage under the growth conditions used
The B. mallei genome is nearly identical to that of B. pseudomallei, differing by several contiguous gene clusters in B. pseudomallei that appear to have been deleted from B. mallei, and it is hypothesized that B. mallei evolved from a single B. pseudomallei strain [8,9]
Summary
Burkholderia species exhibit enormous phenotypic diversity, ranging from the nonpathogenic, soiland water-inhabiting Burkholderia thailandensis to the virulent, host-adapted mammalian pathogen B. mallei. Individual isolates of Burkholderia pseudomallei and B. thailandensis, for example, carry a variety of strain-specific genomic islands (GIs), including putative pathogenicity and metabolic islands, prophage-like islands, and prophages. These GIs may provide some strains with a competitive advantage in the environment and/or in the host relative to other strains. B. pseudomallei isolates are genetically quite diverse [4,5], and this heterogeneity may be due at least in part to the highly variable distribution of bacteriophages among strains [6] Such differences may provide certain strains survival advantages in the environment and the host, as well as explain the variable clinical presentation of melioidosis
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