Multiple replicons constitute the 6.5-megabase genome of Burkholderia pseudomallei

Burkholderia pseudomallei is a causative agent of melioidosis, a fatal trop ical infectious disease endemic in Southeast Asia and Northern Australia. I n order to determine the size and characteristics of the bacterial genome, the B. pseudomallei genome and genes were analyzed by pulsed field gel elec trophoresis of the undigested, intact megabase DNA, and by computational an alysis of nucleotide sequences of B. pseudomallei genes which have been seq uenced by several investigators and already deposited in a public database. The results showed that the B. pseudomallei genome consists of two large r eplicons, and that both contain ribosomal RNA gene sequences, indicating th e presence of two chromosomes. The classical arabinose-negative B. pseudoma llei isolate K96243 has chromosomes of approximately 3563 +/- 73 and 2974 /- 40 kilobase-pairs in size, giving a total genome size of about 6.5 milli on base-pairs. The arabinose-positive nonvirulent biotype of B. pseudomalle i also has two replicons which are smaller than those of the arabinose-nega tive biotype. Analysis of the publicly-available nucleotide sequences showe d that the average B. pseudomallei gene is approximately 1031 base-pairs in size, with an average G + C content of 65.7%. The genome is gene-rich and about 89% of the coding capacity is used as coding sequences. It can theref ore be estimated that the entire B. pseudomallei genome encodes about 5600 genes. (C) 2000 Elsevier Science B.V. All rights reserved.