Burkholderia thailandensis E125 Harbors a Temperate Bacteriophage Specific for Burkholderia mallei

Abstract

Burkholderia thailandensis is a nonpathogenic gram-negative bacillus that is closely related to Burkholderia mallei and Burkholderia pseudomallei . We found that B. thailandensis E125 spontaneously produced a bacteriophage, termed φE125, which formed turbid plaques in top agar containing B. mallei ATCC 23344. We examined the host range of φE125 and found that it formed plaques on B. mallei but not on any other bacterial species tested, including B. thailandensis and B. pseudomallei . Examination of the bacteriophage by transmission electron microscopy revealed an isometric head and a long noncontractile tail. B. mallei NCTC 120 and B. mallei DB110795 were resistant to infection with φE125 and did not produce lipopolysaccharide (LPS) O antigen due to IS 407 A insertions in wbiE and wbiG , respectively. wbiE was provided in trans on a broad-host-range plasmid to B. mallei NCTC 120, and it restored LPS O-antigen production and susceptibility to φE125. The 53,373-bp φE125 genome contained 70 genes, an IS 3 family insertion sequence (IS Bt 3), and an attachment site ( attP ) encompassing the 3′ end of a proline tRNA (UGG) gene. While the overall genetic organization of the φE125 genome was similar to λ-like bacteriophages and prophages, it also possessed a novel cluster of putative replication and lysogeny genes. The φE125 genome encoded an adenine and a cytosine methyltransferase, and purified bacteriophage DNA contained both N6-methyladenine and N4-methylcytosine. The results presented here demonstrate that φE125 is a new member of the λ supergroup of Siphoviridae that may be useful as a diagnostic tool for B. mallei .