ARS | Publication request: Pseudomonas kuykendallii sp. nov.: A novel y-Proteobacteria isolated from a hexazinone degrading bioreactor

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 26, 2012
Publication Date: May 13, 2012
Citation: Hunter, W.J., Manter, D.K. 2012. Pseudomonas kuykendallii sp. nov.: A novel y-Proteobacteria isolated from a hexazinone degrading bioreactor. Current Microbiology. 65:170-175.

Interpretive Summary: The three strains of bacteria, designated strains H2T, H6, and H7, that exhibited similar morphological characteristics and cellular fatty acid profiles were isolated from hexazinone degrading bioreactors that had originally be inoculated with a soil wash solution. The strains all had identical 16S rRNA gene sequences; data indicating that the isolates are related members of the same species. The characteristics of these organisms show that they are members the genus Pseudomonas and that they are related to P. graminis, P. putida and P. stutzeri. The 16S rRNA gene (1498 bp) of the H2T strain differed from that of the type strains for P. graminis, P. putida and P. stutzeri by 1.7, 2.1 and 2.4%, respectively. This similarity confirms that the H2T, H6, and H7 strains are related to P. graminis, P. putida and P. stutzeri but that they are phylogenetically divergent enough to represent a novel species. Normally, bacteria of the same species show a divergence of less than 1%. The major cellular fatty acids present in the H2T strain were C18:1 '7c/C18:1 '6c (34.3%), C16:1 '6c/C16:1 '7c (27.4%), C16:0 (20.6%), C12:0 (7.9%), C12:0 3-OH (4.5%) and C10:0 3-OH 3.1%. The 16S rRNA gene sequences, cellular fatty acid profiles, and phenotypic properties of these strains were consistent with their placement in the genus Pseudomonas and the name Pseudomonas kuykendallii sp. nov. is proposed for these bacteria. These bacteria might be useful as inoculum for the bioremediation of soils or waters contaminated with the herbicide hexazinone or with other related herbicides.

Technical Abstract: Three strains of Gram-negative bacteria designated strains H2T, H6, and H7 were isolated from bioreactors that degraded the herbicide hexazinone. Similar morphological characteristics, cellular fatty acid profiles and 16S rRNA gene sequences show that the isolates are members of the same species. These characteristics also show that the isolates belong to the genus Pseudomonas with P. graminis, P. putida and P. stutzeri as close relatives. The 16S rRNA gene of the H2T strain differed from that of type strains for P. graminis, P. putida and P. stutzeri by 1.7, 2.1 and 2.4%, respectively, indicating that the H2T, H6, and H7 strains are related to P. graminis, P. putida and P. stutzeri but are different enough to represent a novel species. The G + C content of the three strains averaged 61.2 ± 0.8 mol% which is similar to the values reported for P. graminis (61), P. putida (61.6), and P. stutzeri (62.2 to 65.5). The major cellular fatty acids present in the H2T strain were C18:1 '7c/C18:1 '6c (34.3%), C16:1 '6c/C16:1 '7c (27.4%), C16:0 (20.6%), C12:0 (7.9%), C12:0 3-OH (4.5%) and C10:0 3-OH 3.1%. The name Pseudomonas kuykendallii sp. nov. is proposed for these bacteria.