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Applied and Environmental Microbiology, July 2000, p. 2718-2725, Vol. 66, No. 7
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Lon Protease Influences Antibiotic Production and UV Tolerance of Pseudomonas fluorescens Pf-5

Cheryl A. Whistler,1 Virginia O. Stockwell,2 and Joyce E. Loper1,2,3,*

Molecular and Cellular Biology Program1 and Department of Botany and Plant Pathology,2 Oregon State University, and Agricultural Research Service, U.S. Department of Agriculture,3 Corvallis, Oregon

Received 4 January 2000/Accepted 10 April 2000

Pseudomonas fluorescens Pf-5 is a soil bacterium that suppresses plant pathogens due in part to its production of the antibiotic pyoluteorin. Previous characterization of Pf-5 revealed three global regulators, including the stationary-phase sigma factor sigma S and the two-component regulators GacA and GacS, that influence both antibiotic production and stress response. In this report, we describe the serine protease Lon as a fourth global regulator influencing these phenotypes in Pf-5. lon mutants overproduced pyoluteorin, transcribed pyoluteorin biosynthesis genes at enhanced levels, and were more sensitive to UV exposure than Pf-5. The lon gene was preceded by sequences that resembled promoters recognized by the heat shock sigma factor sigma 32 (sigma H) of Escherichia coli, and Lon accumulation by Pf-5 increased after heat shock. Therefore, sigma H represents the third sigma factor (with sigma S and sigma 70) implicated in the regulation of antibiotic production by P. fluorescens. Lon protein levels were similar in stationary-phase and exponentially growing cultures of Pf-5 and were not positively affected by the global regulator sigma S or GacS. The association of antibiotic production and stress response has practical implications for the success of disease suppression in the soil environment, where biological control organisms such as Pf-5 are likely to encounter environmental stresses.

* Corresponding author. Mailing address: Horticultural Crops Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, 3420 N.W. Orchard Ave., Corvallis, OR 97330. Phone: (541) 750-8771. Fax: (541) 750-8764. E-mail: loperj{at}bcc.orst.edu.

Applied and Environmental Microbiology, July 2000, p. 2718-2725, Vol. 66, No. 7
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:

  • Chen, S.-H., Suzuki, C. K., Wu, S.-H. (2008). Thermodynamic characterization of specific interactions between the human Lon protease and G-quartet DNA. Nucleic Acids Res 36: 1273-1287 [Abstract] [Full Text]  
  • Stockwell, V. O., Loper, J. E. (2005). The sigma factor RpoS is required for stress tolerance and environmental fitness of Pseudomonas fluorescens Pf-5. Microbiology 151: 3001-3009 [Abstract] [Full Text]  
  • Liu, T., Lu, B., Lee, I., Ondrovicova, G., Kutejova, E., Suzuki, C. K. (2004). DNA and RNA Binding by the Mitochondrial Lon Protease Is Regulated by Nucleotide and Protein Substrate. J. Biol. Chem. 279: 13902-13910 [Abstract] [Full Text]  
  • Brodhagen, M., Henkels, M. D., Loper, J. E. (2004). Positive Autoregulation and Signaling Properties of Pyoluteorin, an Antibiotic Produced by the Biological Control Organism Pseudomonas fluorescens Pf-5. Appl. Environ. Microbiol. 70: 1758-1766 [Abstract] [Full Text]  


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