Burkholderia tropica sp. nov., a novel nitrogen-fixing, plant-associated bacterium

1 Centro Nacional de Pesquisa de Agrobiologia (EMBRAPA-Agrobiologia), km 47, Seropédica, 23851-970, CP 74505, Rio de Janeiro, Brazil 2 Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Ap. Postal 565-A, Cuernavaca, Morelos, México 3 SASA Experiment Station, Private Bag X02, Mt Edgecombe, KZN, 4300 South Africa 4 GSF – National Research Center for Environment and Health, Institute of Soil Ecology, Department of Rhizosphere Biology, Ingolstädter Landstr.1, D-85764 Neuherberg/Munich, Germany 5 Ecologie Microbienne, UMR CNRS 5557 Université Claude Bernard Lyon I, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne cedex, France Correspondence J. Caballero-Mellado jesuscab{at}cifn.unam.mx In an ecological survey of nitrogen-fixing bacteria isolated from the rhizosphere and as endophytes of sugarcane, maize and teosinte plants in Brazil, Mexico and South Africa, a new phylogenetically homogeneous group of N 2 -fixing bacteria was identified within the genus Burkholderia . This polyphasic taxonomic study included microscopic and colony morphology, API 20NE tests and growth on different culture media at different pH and temperatures, as well as carbon source assimilation tests and whole-cell protein pattern analysis. Analysis of 16S rRNA gene sequences showed 99·2–99·9 % similarity within the novel species and 97·2 % similarity to the closest related species, Burkholderia sacchari . The novel species was composed of four distinct amplified 16S rDNA restriction analysis groups. The DNA–DNA reassociation values within the novel species were greater than 70 % and less than 42 % for the closest related species, B. sacchari . Based on these results and on many phenotypic characteristics, a novel N 2 -fixing species is proposed for the genus Burkholderia , Burkholderia tropica sp. nov., with the type strain Ppe8 T (=ATCC BAA-831 T =LMG 22274 T =DSM 15359 T ). B. tropica was isolated from plants grown in geographical regions with climates ranging from temperate subhumid to hot humid. Abbreviations: ARDRA, amplified 16S rDNA restriction analysis V. M. Reis and P. Estrada-de los Santos contributed equally to this study. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequences of the Burkholderia tropica strains determined in this work are AJ420332 , AY128103 , AY321306 , AY128105 and AY128104 . Detailed Biolog results, ARDRA profiles and an extended 16S rRNA gene-based phylogenetic tree are available as supplementary mate