title: Contribution of gene loss to the pathogenic evolution of Burkholderia pseudomallei and Burkholderia mallei.
abstract: Burkholderia pseudomallei is the causative agent of melioidosis. Burkholderia thailandensis is a closely related species that can readily utilize l-arabinose as a sole carbon source, whereas B. pseudomallei cannot. We used Tn5-OT182 mutagenesis to isolate an arabinose-negative mutant of B. thailandensis. Sequence analysis of regions flanking the transposon insertion revealed the presence of an arabinose assimilation operon consisting of nine genes. Analysis of the B. pseudomallei chromosome showed a deletion of the operon from this organism. This deletion was detected in all B. pseudomallei and Burkholderia mallei strains investigated. We cloned the B. thailandensis E264 arabinose assimilation operon and introduced the entire operon into the chromosome of B. pseudomallei 406e via homologous recombination. The resultant strain, B. pseudomallei SZ5028, was able to utilize l-arabinose as a sole carbon source. Strain SZ5028 had a significantly higher 50% lethal dose for Syrian hamsters compared to the parent strain 406e. Microarray analysis revealed that a number of genes in a type III secretion system were down-regulated in strain SZ5028 when cells were grown in l-arabinose, suggesting a regulatory role for l-arabinose or a metabolite of l-arabinose. These results suggest that the ability to metabolize l-arabinose reduces the virulence of B. pseudomallei and that the genes encoding arabinose assimilation may be considered antivirulence genes. The increase in virulence associated with the loss of these genes may have provided a selective advantage for B. pseudomallei as these organisms adapted to survival in animal hosts.
authors.affiliation: Department of Microbiology and Infectious Diseases, Faculty of Medicine, University of Calgary Health Sciences Centre, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Moore
authors.forename: Shauna
authors.initials: S
authors.lastname: Reckseidler-Zenteno
authors.forename: Heenam
authors.initials: H
authors.lastname: Kim
authors.forename: William
authors.initials: W
authors.lastname: Nierman
authors.forename: Yan
authors.initials: Y
authors.lastname: Yu
authors.forename: Apichai
authors.initials: A
authors.lastname: Tuanyok
authors.forename: Jonathan
authors.initials: J
authors.lastname: Warawa
authors.forename: David
authors.initials: D
authors.lastname: DeShazer
authors.forename: Donald E
authors.initials: DE
authors.lastname: Woods
mesh_terms: D000818:Animals; D001089:Arabinose / Q000378:metabolism; D005075:Biological Evolution; D015152:Blotting, Northern; D042726:Burkholderia mallei / Q000235:genetics* / Q000472:pathogenicity; D016957:Burkholderia pseudomallei / Q000235:genetics* / Q000472:pathogenicity; D006224:Cricetinae; D004195:Disease Models, Animal; D008554:Melioidosis / Q000382:microbiology; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis
chemical_list: D001089:Arabinose