Summary auto-generated
Researchers isolated 29 phenanthrene-degrading bacteria from contaminated soil at a former coal gasification site in Frederiksberg, Denmark. Using phenotypic and genotypic characterization, they determined these isolates belonged to the genus Pseudomonas but represented a previously unknown species. The bacteria were gram-negative rods that did not produce fluorescent pigments on standard media, were oxidase and catalase positive, accumulated poly-β-hydroxybutyrate (PHB), and denitrified. They grew at 4-30°C but not 37°C and had a G+C content of 59.6 mol%. Although 16S rDNA sequencing showed close phylogenetic relationships to several known Pseudomonas species (99.2% homology to P. chlororaphis, 99.0% to P. syringae, and 98.4% to P. corrugata), DNA-DNA hybridization studies revealed less than 35% homology with reference strains, clearly distinguishing this as a new species. Based on these results, the researchers proposed Pseudomonas frederiksbergensis sp. nov., with strain JAJ28T designated as the type strain.
Key findings
- Twenty-nine phenanthrene-degrading bacteria from a coal gasification site represent a new Pseudomonas species, P. frederiksbergensis sp. nov.
- The isolates are non-fluorescent, oxidase-positive, denitrifying bacteria that accumulate PHB and grow at 4-30°C but not at 37°C, distinguishing them from closely related species.
- DNA-DNA hybridization results (all below 35% homology with reference strains) confirmed species-level distinction despite high 16S rDNA sequence similarity (98-99%) to P. chlororaphis, P. syringae, and P. corrugata.
- Type strain JAJ28T has a G+C content of 59.6 mol% and was deposited as DSM 13022T in the DSMZ culture collection.
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Abstract
Phenotypic and genotypic characterization indicated that a group of 29 closely related phenanthrene-degrading bacteria from a coal gasification site in Frederiksberg, Copenhagen, Denmark, belonged to the genus Pseudomonas. The strains were isolated at two sampling occasions 2 years apart. The isolates were phenotypically different from any known species of the genus Pseudomonas and were therefore subject to further identification. Colonies were smooth and pale yellowish and did not produce pigments fluorescent in UV light when grown on King's B agar. Cells were rod-shaped, approximately 0.5--0.8 x 1.5--3.0 microm, and grew at 4 and 30 degrees C, but not 37 degrees C. The bacteria were oxidase- and catalase-positive, accumulated poly-beta-hydroxybutyrate and denitrified, but did not utilize D-xylose. The mean G+C content was 59.6 mol%. Phenotypic data and 16S rDNA sequence data information for Pseudomonas amygdali and Pseudomonas corrugata, and 16S rDNA sequence data for Pseudomonas chlororaphis and Pseudomonas syringae showed close relationships to these strains. However, DNA--DNA hybridization data showed that the isolates belong to a new species, for which the name Pseudomonas frederiksbergensis sp. nov. is proposed. The type strain is JAJ28(T) (DSM 13022(T)).