Transposons for a long time have been integrated themselves into the genomes of their hosts, especially in bacteria like an unwanted guest living in your house. These nomadic sequences have fixated themselves in the host and appear in high frequency when it encounters certain external stimuli. It has been shown that different environmental stresses, such as radiation, temperature and starvation have increased the activity of transpositional elements. However these unwanted houseguest’s aren’t just occupying space, they can enhance the survival of their host when face with a life threatening stress by increasing its genetic variability.
Tn4652 is a 17kb stationary phase specific transposase promoter that occupies PaW85 strains of Pseudomonas putida. Studies of P. putida in starving conditions on phenol plates have shown how mutant strains have activated promoter-less phenol degradation genes in the plasmid pEST1414. The insertion of this element upstream from the target DNA created a fusion promoter that is coincidently activated by physiological stress. The longer the time of starvation was the higher the frequency of the Tn4652. This is the first time a direct stationary phase specific regulation of a mobile element transposase. Truly these transpositional elements aren’t the worst things to be hosts for.
Primary references:
ILVES, H., R. HORAK, and M. KIVISAAR, 2001 Involvement of {sigma}S in starvation-induced transposition of Pseudomonas putida transposon Tn4652.. J. Bacteriol. 183:5445-5448. [online] Available at: http://jb.asm.org/cgi/content/abstract/183/18/5445 (accessed on 8/10/07)
Secondary reference:
Capy, P., G. Gasperi, C. Biemont, and C. Bazin. 2000. Stress and transposable elements: co-evolution or useful parasites? Heredity 85:101-106. [online] Available at: http://www.blackwell-synergy.com/doi/ref/10.1046/j.1365-2540.2000.00751.x?cookieSet=1 (accessed on 8/10/07)
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