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Applied and Environmental Microbiology, April 2008, p. 2398-2403, Vol. 74, No. 8
0099-2240/08/$08.00+0     doi:10.1128/AEM.02457-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Requirement of a Plasmid-Encoded Catalase for Survival of Rhizobium etli CFN42 in a Polyphenol-Rich Environment{triangledown}

Alejandro García-de los Santos,1* Erika López,1 Ciro A. Cubillas,1 K. Dale Noel,2 Susana Brom,1 and David Romero1

Programa de Ingeniería Genómica, Centro de Ciencias Genómicas, UNAM, Cuernavaca, Morelos, Mexico,1 Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin2

Received 31 October 2007/ Accepted 15 February 2008

Nitrogen-fixing bacteria collectively called rhizobia are adapted to live in polyphenol-rich environments. The mechanisms that allow these bacteria to overcome toxic concentrations of plant polyphenols have not been clearly elucidated. We used a crude extract of polyphenols released from the seed coat of the black bean to simulate a polyphenol-rich environment and analyze the response of the bean-nodulating strain Rhizobium etli CFN42. Our results showed that the viability of the wild type as well as that of derivative strains cured of plasmids p42a, p42b, p42c, and p42d or lacking 200 kb of plasmid p42e was not affected in this environment. In contrast, survival of the mutant lacking plasmid p42f was severely diminished. Complementation analysis revealed that the katG gene located on this plasmid, encoding the only catalase present in this bacterium, restored full resistance to testa polyphenols. Our results indicate that oxidation of polyphenols due to interaction with bacterial cells results in the production of a high quantity of H2O2, whose removal by the katG-encoded catalase plays a key role for cell survival in a polyphenol-rich environment.

* Corresponding author. Mailing address: Programa de Ingeniería Genómica, Centro de Ciencias Genómicas, UNAM. Ap. Postal 565-A, Cuernavaca, Morelos, Mexico. Phone: (52) (777) 329 16 91. Fax: (52) (777) 317 55 81. E-mail: alex{at}ccg.unam.mx

{triangledown} Published ahead of print on 29 February 2008.

Applied and Environmental Microbiology, April 2008, p. 2398-2403, Vol. 74, No. 8
0099-2240/08/$08.00+0     doi:10.1128/AEM.02457-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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