Burkholderia heleia sp. nov., a nitrogen-fixing bacterium isolated from an aquatic plant, Eleocharis dulcis, that grows in highly acidic swamps in actual acid sulfate soil areas of Vietnam

Nitrogen-fixing bacteria, strains SA41^T, SA42 and SA53, were isolated from an aquatic plant, Eleocharis dulcis, that grows in highly acidic swamps (pH 2-4) in actual acid sulfate soil areas of Vietnam. The isolates were Gram-negative, aerobic, non-spore-forming, rod-shaped bacteria, having a cell width of 0.6-0.7 mm and a length of 1.5-1.7 μm. They showed good growth between pH 3.0 and 7.0, and between 17 and 37°C. The organisms contained ubiquinone Q-8 as the predominant isoprenoid quinone, and C_{16 : 0}, C_{17 : 0} cyclo, C_{18 : 1} ω7c and summed feature 3 (C_{16 : 1} ω7c and/or iso-C_{15 : 0} 2-OH) as major fatty acids. Their fatty acid profiles are similar to those reported for other Burkholderia species. The DNA G+C content of these strains was 64 mol%. On the basis of 16S rRNA gene sequence similarity, these strains were shown to belong to the genus Burkholderia. Although their calculated 16S rRNA gene sequence similarity values to Burkholderia silvatlantica, Burkholderia mimosarum, Burkholderia ferrariae and Burkholderia tropica were 98.5, 98.2, 98.0 and 97.0 %, respectively, the isolates formed a distinct group in phylogenetic trees, and the DNA-DNA relatedness values of strain SA41^T to these species were 39, 41, 39 and 33 %, respectively. The results of physiological and biochemical tests, including whole-cell protein pattern analysis, allowed phenotypic differentiation of these strains from the published Burkholderia species. Therefore, strains SA41^T, SA42 and SA53 represent a novel species for which the name Burkholderia heleia sp. nov. is proposed. The type strain is SA41^T (=NBRC 101817^T=VTCC-D6-7^T).