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Journal of Bacteriology, June 2008, p. 4328-4334, Vol. 190, No. 12
0021-9193/08/$08.00+0     doi:10.1128/JB.00183-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Protective Action of ppGpp in Microcin J25-Sensitive Strains{triangledown}

María Fernanda Pomares,{dagger} Paula A. Vincent,{dagger} Ricardo N. Farías, and Raúl A. Salomón*

Departamento de Bioquímica de la Nutrición, Instituto Superior de Investigaciones Biológicas (Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Tucumán) and Instituto de Química Biológica "Dr Bernabé Bloj", Chacabuco 461, 4000 San Miguel de Tucumán, Tucumán, Argentina

Received 6 February 2008/ Accepted 2 April 2008

As Escherichia coli strains enter the stationary phase of growth they become more resistant to the peptide antibiotic microcin J25. It is known that starvation for nutrients such as amino acids or glucose leads to increases in guanosine 3',5'-bispyrophosphate (ppGpp) levels and that the intracellular concentration of this nucleotide increases as cells enter the stationary phase of growth. Therefore, we examined the effects of artificially manipulating the ppGpp levels on sensitivity to microcin J25. A direct correlation was found between ppGpp accumulation and microcin resistance. Our results indicate that the nucleotide is required to induce production of YojI, a chromosomally encoded efflux pump which, in turn, expels microcin from cells. This would maintain the intracellular level of the antibiotic below a toxic level.

* Corresponding author. Mailing address: Departamento de Bioquímica de la Nutrición, INSIBIO, Chacabuco 461, 4000 San Miguel de Tucumán, Argentina. Phone and fax: (54) (381) 4248921. E-mail: salomon{at}fbqf.unt.edu.ar

{triangledown} Published ahead of print on 11 April 2008.

{dagger} M.F.P. and P.A.V. contributed equally to this study.

Journal of Bacteriology, June 2008, p. 4328-4334, Vol. 190, No. 12
0021-9193/08/$08.00+0     doi:10.1128/JB.00183-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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