Diversity of Burkholderia isolates from woodland rhizosphere environments

Aims: Determination of genetic diversity among UK Burkholderia cepacia isolates from various environmental niches, principally woodland tree rhizospheres and onions. Methods and Results: Genus determination was made using polymerase chain reaction (PCR) amplification and fatty acid methyl ester profiling. Genetic diversity was investigated by repetitive sequence genetic PCR fingerprinting. Several onion isolates were similar to clinical isolates but others were diverse. Some environmental isolates were possibly synonymous with B. cepacia and B. gladioli but most from woodland rhizospheres were distinct and clustered together. The 16S rRNA genes of representatives from these clusters were PCR amplified, sequenced and phylogenetically compared with all known Burkholderia and related species. This revealed that the rhizospheric isolates had closest affinity with Burkholderia spp. with known bioremediative and biocontrol capabilities and were unrelated to taxa comprising plant or human pathogenic strains. Conclusions: All of the analyses investigated revealed that environmental and onion isolates of B. cepacia complex bacteria are genetically diverse but that woodland rhizospheric isolates are related to each other and unrelated to plant or human pathogenic strains. Significance and Impact of the Study: Woodland rhizospheric isolates of B. cepacia are potentially good candidates for use in bioremediation and biocontrol, as they appear distinct from plant or human pathogenic strains.