title: Laccase activity in melanin-producing strains of Sinorhizobium meliloti.
abstract: Laccase-like activity was detected in melanin-producing strains of Sinorhizobium meliloti mainly in cells at the stationary growth phase when copper was added to the medium. The laccase showed both syringaldazine and ABTS (2,2'-azino-bis-ethylbenzthiazoline-6-sulfonic acid) oxidase activities and was activated by the addition of 1.7 mM sodium dodecyl sulfate. Activity was totally inhibited by the addition of 1.0 mM EDTA, suggesting that the enzyme is a metal-dependent one. The enzyme was found to be cytosolic having an optimum pH of 5.0, an estimated molecular mass of 95 kDa and a K(m) of 4 microM for syringaldazine. Both laccase and tyrosinase activities were detected in melanin-producing S. meliloti strains. Plant growth-promoting (PGP) effect in rice by a laccase-producing S. meliloti strain when co-inoculated with Azospirillum brasilense Cd was observed. PGP effect by co-inoculation significantly increased plant yield compared to A. brasilense by itself. To the best of our knowledge this is the first report on laccase production in rhizobia and cooperation between Azospirillum and Sinorhizobium in rice.
authors: Departamento de Bioquímica, Instituto de Investigaciones Biológicas Clemente Estable, Unidad Asociada de Bioquímica, Instituto de Biología, Facultad de Ciencias, Universidad de la República, Av. Italia 3318, Montevideo, Uruguay. scs@iibce.edu.uy
authors: Susana
authors: S
authors: Castro-Sowinski
authors: Gloria
authors: G
authors: Martinez-Drets
authors: Yaacov
authors: Y
authors: Okon
mesh_terms: D015806:Azospirillum brasilense / Q000502:physiology; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D052160:Benzothiazoles; D003300:Copper / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006835:Hydrazones / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D042845:Laccase; D008543:Melanins / Q000096:biosynthesis*; D008970:Molecular Weight; D014442:Monophenol Monooxygenase / Q000378:metabolism; D012275:Oryza / Q000254:growth & development / Q000382:microbiology; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D016962:Sinorhizobium meliloti / Q000201:enzymology* / Q000502:physiology; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013045:Species Specificity; D013379:Substrate Specificity; D013451:Sulfonic Acids / Q000378:metabolism; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D052160:Benzothiazoles; D006835:Hydrazones; D008543:Melanins; D013451:Sulfonic Acids; C009370:syringaldazine; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D012967:Sodium Dodecyl Sulfate; D003300:Copper; D004492:Edetic Acid; D010088:Oxidoreductases; D042845:Laccase; D014442:Monophenol Monooxygenase