title: Lon protease influences antibiotic production and UV tolerance of Pseudomonas fluorescens Pf-5.
abstract: 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.
authors.affiliation: Molecular and Cellular Biology Program, Corvallis, Oregon.
authors.forename: C A
authors.initials: CA
authors.lastname: Whistler
authors.forename: V O
authors.initials: VO
authors.lastname: Stockwell
authors.forename: J E
authors.initials: JE
authors.lastname: Loper
mesh_terms: D049069:ATP-Dependent Proteases; D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D001426:Bacterial Proteins; D001483:Base Sequence; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018869:Heat-Shock Response; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010636:Phenols; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D049070:Protease La; D011551:Pseudomonas fluorescens / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D011758:Pyrroles; D011836:Radiation Tolerance; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; D006360:Heat-Shock Proteins; D010636:Phenols; D011758:Pyrroles; D012808:Sigma Factor; D014157:Transcription Factors; C069774:heat-shock sigma factor 32; C095503:pyoluteorin; D017853:Phosphotransferases (Alcohol Group Acceptor); D049069:ATP-Dependent Proteases; D012697:Serine Endopeptidases; C483567:Lon protein, E coli; D049070:Protease La