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The Pseudomonas aeruginosa genome
Ubiquitous bacterium sequenced
  
By Bijal P. Trivedi

The bacterium Pseudomonas aeruginosa preys on victims with compromised immune systems; it is one of the top three leading causes of opportunistic infection among cystic fibrosis patients, burn victims, and patients on respirators. And it is resistant to antibiotics. But now researchers have the ultimate weapon in their long-standing battle against P. aeruginosa: the sequence of its entire genome.

P. aeruginosa is an extremely versatile bacterium and lives almost anywhere—in water, soil, plants and animals—and can use almost anything for food. The source of this adaptability lies within its genome, which—at 6.3 million chemical units—is larger than the other 25 bacterial genomes sequenced to date.

The sequence has been annotated by a group of 61 P. aeruginosa experts who were assembled to find genes within the bacterium. Using gene-finder computer programs and known genes from other organisms as bait, the researchers predict that P. aeruginosa contains 5,570 genes. Their findings are published in the current issue of Nature.

The expectation is that the genes will help scientists understand the biology of the bacterium and allow them target their drugs at specific genes or proteins.

The two most surprising aspects of the annotation to emerge from the analysis are that 8 to 10 percent of the genes are responsible for the regulation of other genes—essentially turning them on and off. This feature enables the genes to be activated in countless combinations, which could explain how this bacterium adapts to innumerable environments.

The scientists also identified 10 protein pumps, which sit on the outer membrane of the bacterium. Researchers hypothesize that P. aeruginosa's resistance to detergents and antibiotics may result from the pumps saving the bacterium from antibiotics that are meant to wipe it out.

Sequencing P. aeruginosa was a collaborative effort by a group of academic scientists, the US Cystic Fibrosis Foundation and the PathoGenesis Corporation.

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Stover, C.K. et al. Complete genome sequence of Pseudomonas aeruginosa PA01, an opportunistic pathogen. Nature 406, 959-964 (August 31, 2000).
 

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