Effect of Root-Derived Substrates on the Expression of nah-lux Genes in Pseudomonas fluorescens HK44: Implications for PAH Biodegradation in the Rhizosphere

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• 作者：Roopa Kamath ; Jerald L. Schnoor ; and Pedro J. J. Alvarez
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：March 15, 2004
• 年：2004
• 卷：38
• 期：6
• 页码：1740 - 1745
• 全文大小：94K
• 年卷期：v.38,no.6(March 15, 2004)
• ISSN：1520-5851

文摘

The bioluminescent reporter strain Pseudomonas fluorescens HK44 with a nah-lux fusion, was used to investigatethe effect of root material (from hybrid poplars, willow,kou, milo, Osage orange, mulberry, and switch grass) andpotential root-derived substrates (e.g., sugars, carboxylicacids, amino acids, and phenolics) on the expression of nahG,one of the genes responsible for naphthalene dioxygenasetranscription. Whereas nahG was induced by somephenolic substrates that could be released by plants (i.e.,salicylate, methyl salicylate, and acetyl salicylate), noinduction by root extracts was observed. Rather, increasingroot extract concentrations (50 to 275 mg L^-1 as totalorganic carbon) inhibited nahG expression in assays withcells concurrently exposed to naphthalene. Root extractsalso decreased nahG expression at the individual cell levelduring naphthalene degradation assays. However,treatments with root extracts exhibited significantly highermicrobial growth and overall bioluminescence, indicatinga higher level of nahG expression by the resulting largermicrobial population. This generally resulted in fasternaphthalene degradation rates, suggesting that plant-promoted proliferation of competent genotypes couldcompensate for the interference that labile substratesexert on the expression of genes that code for the degradationof polynuclear aromatic hydrocarbons (PAHs). This couldexplain the faster PAH degradation commonly reported inplanted than in unplanted soils.