Burkholderia humptydooensis sp. nov., a New Species Related to Burkholderia thailandensis and the Fifth Member of the Burkholderia pseudomallei Complex

During routine screening for endemic Burkholderia pseudomallei from water wells in northern Australia, Gram-staining-negative bacteria (strains MSMB43 T , MSMB121, and MSMB122) with a similar morphology and biochemical pattern to B. pseudomallei and B. thailandensis were co-isolated with B. pseudomallei on Ashdown9s selective agar. To determine the exact taxonomic position of these strains and to distinguish them from B. pseudomallei and B. thailandensis , they were subjected to a series of phenotypic and molecular analyses. Biochemical and fatty acid methyl esters analysis was unable to distinguish B. humptydooensis sp. nov. from closely related species. In MALDI-TOF analysis, all isolates grouped together in a cluster separate from other Burkholderia spp. 16S rRNA and recA sequence analysis demonstrated phylogenetic placement for B. humptydooensis sp. nov. in a novel clade within the B. pseudomallei group. MLST analysis of the three isolates in comparison with MLST data from 3,340 B. pseudomallei strains and related taxa revealed a new sequence type (ST318). Genome to genome distance calculations and average nucleotide identity of all isolates to both B. thailandensis and B. pseudomallei , based on whole genome sequences, also confirmed B. humptydooensis sp. nov. as a novel Burkholderia species within the pseudomallei complex. Molecular analyses clearly demonstrate that strains MSMB43 T , MSMB121, and MSMB122 belong to a novel Burkholderia species for which the name Burkholderia humptydooensis sp. nov. is proposed with the type strain MSMB43 T (=BAA-2767; LMG 29471, CP013380-CP013382). IMPORTANCE Burkholderia pseudomallei is a soil dwelling bacteria and the causative agent of melioidosis. The genus Burkholderia consists of a diverse group of species with the closest relatives of B. pseudomallei referred to as the B. pseudomallei complex. A proposed novel species, B. humptydooensis sp. nov, was isolated from a bore water sample from the Northern Territory in Australia. B. humptydooensis sp. nov., is phylogenetically distinct from B. pseudomallei and other members of the pseudomallei complex making it the fifth member of this important group of bacteria.