Abstract
Pulsed-field gel electrophoresis and 16S rRNA hybridization experiments showed that multichromosome genome structures and very large genome sizes (6.46 to 8.73 Mb) are prevalent in novel plant-associated Burkholderia species. (15)N(2) isotope dilution assays revealed unambiguous diazotrophy in these novel species. nifH gene sequence analysis, often used to determine phylogenetic relatedness among diazotrophs, showed tight clusters of Burkholderia species, which were clearly distinct from those of other diazotrophs.