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Multiple replicons constitute the 6.5-megabase genome of Burkholderia pseudomallei
1Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand. sissv@mahidol.ac.th
Abstract:
Burkholderia pseudomallei is a causative agent of melioidosis, a fatal tropical infectious disease endemic in Southeast Asia and Northern Australia. In order to determine the size and characteristics of the bacterial genome, the B. pseudomallei genome and genes were analyzed by pulsed field gel electrophoresis of the undigested, intact megabase DNA, and by computational analysis of nucleotide sequences of B. pseudomallei genes which have been sequenced by several investigators and already deposited in a public database. The results showed that the B. pseudomallei genome consists of two large replicons, and that both contain ribosomal RNA gene sequences, indicating the presence of two chromosomes. The classical arabinose-negative B. pseudomallei isolate K96243 has chromosomes of approximately 3563 +/- 73 and 2974 +/- 40 kilobase-pairs in size, giving a total genome size of about 6.5 million base-pairs. The arabinose-positive nonvirulent biotype of B. pseudomallei also has two replicons which are smaller than those of the arabinose-negative biotype. Analysis of the publicly-available nucleotide sequences showed 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 therefore be estimated that the entire B. pseudomallei genome encodes about 5600 genes.
Insights
Burkholderia pseudomallei, the cause of melioidosis, possesses a two-chromosome genome. This bacterial genome is gene-rich, with approximately 5600 genes, and its size varies between different biotypes.
Area of Science:
- Microbiology
- Genomics
- Infectious Diseases
Background:
- Melioidosis is a fatal tropical disease caused by Burkholderia pseudomallei.
- Understanding the bacterial genome is crucial for studying infectious agents.
Purpose of the Study:
- To determine the size and characteristics of the Burkholderia pseudomallei genome.
- To analyze the gene content and organization of this important pathogen.
Main Methods:
- Pulsed field gel electrophoresis of intact bacterial DNA.
- Computational analysis of publicly available nucleotide sequences of B. pseudomallei genes.
Main Results:
- The B. pseudomallei genome comprises two large replicons (chromosomes), both containing ribosomal RNA genes.
- The arabinose-negative K96243 isolate has a total genome size of approximately 6.5 million base-pairs.
- The genome is gene-rich, encoding an estimated 5600 genes with an average G+C content of 65.7%.
Conclusions:
- Burkholderia pseudomallei possesses a unique two-chromosome genome structure.
- Genome size and characteristics differ between virulent and nonvirulent biotypes.
- The gene-rich nature of the genome provides insights into its biological capabilities.