The Cross-Border Biotech Blog

Biotechnology, Health and Business in Canada, the United States and Worldwide

Friday Science Review: October 5, 2012

What happens to the genome of pathogenic bacteria when they are forced to adapt after being confronted by an antibiotic, or after colonizing a new host species? This was the question posed by the Kassen lab at Carleton University. In their study, published in PLoS Genetics, they exposed Pseudomonas aeruginosa, an opportunistic pathogen and the major pathogen in the lungs of cystic fibrosis sufferers, to antibiotics in CF-lung mimicking culture conditions and then used by whole-genome sequencing to follow the genomic basis of the bacteria’s adaptation.

As might be expected, they found changes in antibiotic resistance genes that correlated with the degree of antibiotic resistance of the particular experimental isolate. However, they also found other co-occurring mutations that played a role in antibiotic resistance, but that had different associated fitness costs, suggesting a wide range of compensatory mutations. Separately, the study was able to add to the body of evidence suggesting that cyclic-di-GMP signaling plays a role in the adaptation of the bacteria to CF-lung-like conditions – a signaling pathway that promotes the adoption of a biofilm phenotype rather than the motile planktonic phenotype.

Ultimately, the study shows that adaptation of an opportunistic pathogen to conditions reproducing its common host environment results in a mixture of expected and unexpected genetic adaptations. These adaptations represent new targets for therapies, but also illustrate the heterogeneity facing patients and clinicians as they try to address these infections in the clinic.

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