title: Characterization of melanin-overproducing transposon mutants of Pseudomonas putida F6.
abstract: Two melanin-overproducing Pseudomonas putida F6 mutants were generated using transposon (Tn5) mutagenesis. Mutants were disrupted in a transcriptional regulator (TR) and a homogentisate 1,2-dioxygenase (HDO) gene. Colonies of mutant F6-TR overproduced a black pigment on solid medium. The same mutant (F6-TR) had a 3.7-fold higher tyrosinase activity compared with the wild-type strain when induced with ferulic acid. However in tyrosine uptake assays whole cells of the mutant strain F6-TR consumed eight times less tyrosine compared with the wild-type strain. Mutant F6-HDO produced a diffusible red pigment into the growth medium. Pigment production by mutant F6-HDO is sixfold higher than the wild-type strain. The biomass yield of mutant F6-HDO grown on tyrosine as the sole source of carbon and energy was 1.2-fold lower than the wild-type strain. While the growth of the wild-type strain was completely inhibited by 5 min of exposure to UV light (254 nm) both mutant strains showed survival rates >30%. Mutant F6-HDO was able to tolerate higher concentrations of hydrogen peroxide (H(2)O(2)) exhibiting 1.5 times smaller zones of inhibition at 10 mM H(2)O(2) compared with mutant F6-TR and the wild-type strain. The pigments produced by all strains were purified and confirmed to be melanins.
authors.affiliation: School of Biomolecular and Biomedical Sciences, University College Dublin, Dublin, Ireland.
authors.forename: Jasmina
authors.initials: J
authors.lastname: Nikodinovic-Runic
authors.forename: Leona B
authors.initials: LB
authors.lastname: Martin
authors.forename: Ramesh
authors.initials: R
authors.lastname: Babu
authors.forename: Werner
authors.initials: W
authors.lastname: Blau
authors.forename: Kevin E
authors.initials: KE
authors.lastname: O'Connor
mesh_terms: D018533:Biomass; D003373:Coumaric Acids / Q000378:metabolism; D004251:DNA Transposable Elements; D050560:Homogentisate 1,2-Dioxygenase / Q000235:genetics; D006861:Hydrogen Peroxide / Q000633:toxicity; D008543:Melanins / Q000096:biosynthesis*; D050296:Microbial Viability / Q000528:radiation effects; D014442:Monophenol Monooxygenase / Q000378:metabolism; D016254:Mutagenesis, Insertional / Q000379:methods; D016958:Pseudomonas putida / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D014157:Transcription Factors / Q000235:genetics; D014443:Tyrosine / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D003373:Coumaric Acids; D004251:DNA Transposable Elements; D008543:Melanins; D014157:Transcription Factors; D014443:Tyrosine; C004999:ferulic acid; D006861:Hydrogen Peroxide; D050560:Homogentisate 1,2-Dioxygenase; D014442:Monophenol Monooxygenase