Novel Burkholderia bacteria isolated from Lebeckia ambigua – A perennial suffrutescent legume of the fynbos

We investigated symbiotic and physiological properties, and taxonomic position, of 23 bacterial strains isolated from Lebeckia ambigua root nodules collected from the South African fynbos region. The capacity for nodulation and nitrogen fixation on three provenances of L. ambigua was investigated for these strains together with several physiological characters, including growth rate on peat and in betonite clay, survival on polyethylene beads and pH tolerance. Additionally, the 16S rRNA gene phylogeny was determined. The root nodule bacteria isolated clustered in five different groups belonging to the genus Burkholderia, most closely related to B. caledonica, B. graminis and B. tuberum. Moreover there was a very strong influence of collection site on the taxonomy of the Burkholderia strains. The physiological characterisation revealed two promising strains, WSM4174 and WSM4184, achieved rapid growth in normal media and reached high, stable numbers in sterile peat. However, there was a worrying susceptibility to desiccation amongst these Burkholderia. Additionally, evidence was found for isolation of non-symbiotic strains from the nodule material collected in South Africa.