Exploring the differential evolutionary origins of the two Burkholderia pseudomallei chromosomes

Abstract

The complete genome sequence of B.pseudomallei has recently been reported. This is composed of two chromosomes of 4.07 megabases and 3.17 megabases. There is significant functional partitioning between them; the large chromosome encodes more of the core functions associated with cell metabolism, while the small chromosome carries more accessory function genes. The large chromosome also demonstrates a greater level of gene order conservation and a greater number of orthologous genes when compared with other related bacteria, suggesting that the two replicons may have different evolutionary origins. The objective of this study was to explore this further by comparing gene sequence fragments from conserved housekeeping genes contained on the first and second chromosome for 180 B.pseudomallei isolates associated with human disease or obtained from soil.