Bacterial genome adaptation to niches: divergence of the potential virulence genes in three Burkholderia species of different survival strategies.
BACKGROUND
Two closely related species Burkholderia mallei (Bm) and Burkholderia pseudomallei (Bp) are serious human health hazards and are potential bio-warfare agents, whereas another closely related species Burkholderia thailandensis (Bt) is a non-pathogenic saprophyte. To investigate the genomic factors resulting in such a dramatic difference, we first identified the Bm genes responsive to the mouse environment, and then examined the divergence of these genes in Bp and Bt.


RESULTS
The genes down-expressed, which largely encode cell growth-related proteins, are conserved well in all three species, whereas those up-expressed, which include potential virulence genes, are less well conserved or absent notably in Bt. However, a substantial number of up-expressed genes is still conserved in Bt. Bm and Bp further diverged from each other in a small number of genes resulting from unit number changes in simple sequence repeats (ssr) in the homologs.


CONCLUSIONS
Our data suggest that divergent evolution of a small set of genes, rather than acquisition or loss of pathogenic islands, is associated with the development of different life styles in these bacteria of similar genomic contents. Further divergence between Bm and Bp mediated by ssr changes may reflect different adaptive processes of Bm and Bp fine-tuning into their host environments.
Kim
H Stanley
HS
The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850, USA. hkim@tigr.org
Schell
Mark A
MA
Yu
Yan
Y
Ulrich
Ricky L
RL
Sarria
Saul H
SH
Nierman
William C
WC
DeShazer
David
D
D000818:Animals; D019117:Burkholderia / Q000166:cytology / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D019121:Burkholderia Infections / Q000473:pathology; D002470:Cell Survival; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D004269:DNA, Bacterial / Q000235:genetics; D016680:Genome, Bacterial; D008099:Liver / Q000382:microbiology; D051379:Mice; D009693:Nucleic Acid Hybridization; D013154:Spleen / Q000382:microbiology; D014774:Virulence / Q000235:genetics*
D004269:DNA, Bacterial