Comparative genomic analysis of two Burkholderia glumae strains from different geographic origins reveals a high degree of plasticity in genome structure associated with genomic islands

Burkholderia glumae is the major causal agent of bacterial panicle blight of rice, a growing disease problem in global rice production. To better understand its genome-scale characteristics, the genome of the highly virulent B. glumae strain 336gr-1 isolated from Louisiana, USA was sequenced using the Illumina Genome Analyser II system. De novo assembled 336gr-1 contigs were aligned and compared with the previously sequenced genome of B. glumae strain BGR1, which was isolated from an infected rice plant in South Korea. Comparative analysis of the whole genomes of B. glumae 336gr-1 and B. glumae BGR1 revealed numerous unique genomic regions present only in one of the two strains. These unique regions contained accessory genes including mobile elements and phage-related genes, and some of the unique regions in B. glumae BGR1 corresponded to predicted genomic islands. In contrast, little variation was observed in known and potential virulence genes between the two genomes. The considerable amount of plasticity largely based on accessory genes and genome islands observed from the comparison of the genomes of these two strains of B. glumae may explain the versatility of this bacterial species in various environmental conditions and geographic locations.