Physiological role of NahW, the additional salicylate hydroxylase found in Pseudomonas stutzeri AN10.
The physiological role of NahW, the second salicylate hydroxylase of Pseudomonas stutzeri AN10, has been analysed by gene mutation and further complementation. When grown on naphthalene as a unique carbon and energy source, the nahW mutant showed a strong decrease in salicylate hydroxylase activity when compared with the wild-type strain, exhibited lower specific growth rates and accumulated salicylate in culture supernatants. Similarly, lower specific growth rates and salicylate accumulation were observed for the nahW mutant when growth on naphthalene supplemented with succinate or pyruvate. When P. stutzeri AN10 was grown in Luria-Bertani medium in the presence of salicylate, or was cultivated on minimal medium supplemented with salicylate as a unique carbon and energy source, an increase in the lag phase and a decrease in the specific growth rate were observed on increasing the salicylate concentrations, suggesting a plausible toxic effect. This toxic effect of salicylate was much more evident for the nahW mutant than for the wild-type strain. Complementation of the nahW mutant restored all growth parameters. These results indicate that NahW may have two functions in P. stutzeri AN10: (1) to improve its capacity to degrade naphthalene and (2) effectively convert the salicylate produced during naphthalene degradation to tricarboxylic acid cycle intermediates, preventing its toxic effect.
Microbiologia, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa, km 7.5, Palma de Mallorca, Spain.
Mariana P
MP
Lanfranconi
Joseph A
JA
Christie-Oleza
Cèlia
C
Martín-Cardona
Lady Y
LY
Suárez-Suárez
Jorge
J
Lalucat
Balbina
B
Nogales
Rafael
R
Bosch
D055786:Gene Knockout Techniques; D005816:Genetic Complementation Test; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000502:physiology*; D009281:Naphthalenes / Q000378:metabolism; D044223:Pseudomonas stutzeri / Q000201:enzymology* / Q000235:genetics; D019289:Pyruvic Acid / Q000378:metabolism; D012459:Salicylates / Q000378:metabolism; D019802:Succinic Acid / Q000378:metabolism
D009281:Naphthalenes; D012459:Salicylates; C031721:naphthalene; D019289:Pyruvic Acid; D019802:Succinic Acid; D006899:Mixed Function Oxygenases; C022619:salicylate 1-monooxygenase