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Regulatory Rewiring Improves Bacterial Fitness

3rd December, 2015

Staff in Genetics and Microbiology publish new scientific paper.

Knowledge of the regulatory circuits that govern the high-level global control processes that influence bacterial gene expression has been exploited to produce an organism that outperforms its natural ancestor under specific environmental conditions. No new genes were added and none was removed. Instead, the open reading frames of the genes encoding the H-NS and StpA nucleoid-associated proteins were exchanged on the chromosome of the bacterium Salmonella enterica. The new strain has enhanced competitive fitness that is tuneable by temperature and osmolarity. Although fitter than its natural ancestor under laboratory growth conditions, the new organism does less well under conditions found outside the lab, especially at low temperatures. The chromosome of the rewired organism is free from compensatory mutations. The basis for the change in fitness involves a rescheduling of the appearance of the stress and stationary-phase sigma factor, RpoS. This important component of RNA polymerase now appears in the early exponential phase of growth, hours earlier than it doe sin the ancestor. This work, funded by Science Foundation Ireland, was published online on December 3rd in Scientific Reports (Nature Publishing Group). The paper can be read at:

Fitzgerald S, SC Dillon, C Tzu-Chiao, HL Wiencko, K Hokamp, ADS Cameron, CJ Dorman. 2015. Re-engineering cellular physiology by rewiring high-level global regulatory genes. Scientific Reports 5, 17653; doi: 10.1038/srep17653