No abstract

No abstract

No abstract

Carbamazepine (CBZ) is an environmentally recalcitrant compound highly stable in soil and during wastewater treatment. In this study, we examined the mechanisms by which the white-rot fungus Pleurotus ostreatus metabolizes CBZ in liquid culture using a physiological approach. P. ostreatus PC9 was grown in media known to support different levels of a multiplicity of enzyme systems such as cytochrome P450 (CYP450) and manganese peroxidase (MnP). When both CYP450 and MnP systems were active, 99% of the added CBZ was eliminated from the solution and transformed to 10,11-epoxycarbamazepine. High removal of CBZ was also obtained when either MnP or CYP450 was active. When both CYP450 and MnP were inactivated, only 10 to 30% of the added CBZ was removed. In this latter system, removal of CBZ might be partially attributed to the activity of versatile peroxidase. P. ostreatus was able to eliminate CBZ in liquid culture even when CBZ was added at an environmentally relevant concentration (1 μg L(-1)). On the basis of our study, we suggest that two families of enzymes are involved in the oxidation of CBZ in liquid culture: MnP in a Mn(2+)-dependent or independent manner and CYP450. Our study also highlights the potential of using P. ostreatus for bioremediation systems.

We show that volatile organic compounds (VOCs) produced by rhizospheric strains Pseudomonas fluorescens B-4117 and Serratia plymuthica IC1270 may act as inhibitors of the cell-cell communication quorum-sensing (QS) network mediated by N-acyl homoserine lactone (AHL) signal molecules produced by various bacteria, including strains of Agrobacterium, Chromobacterium, Pectobacterium and Pseudomonas. This quorum-quenching effect was observed when AHL-producing bacteria were treated with VOCs emitted by strains B-4117 and IC1270 or with dimethyl disulfide (DMDS), the major volatile produced by strain IC1270. LC-MS/MS analysis revealed that treatment of strains Pseudomonas chlororaphis 449, Pseudomonas aeruginosa PAO1 or Ps. fluorescens 2-79 with VOCs emitted by strain IC1270 or DMDS drastically decreases the amount of AHLs produced by these bacteria. Volatile organic compounds produced by Ps. chlororaphis 449 were able to suppress its own QS-induction activity, suggesting a negative interaction between VOCs and AHL molecules in the same strain. Quantitative RT-PCR analysis showed that treatment of Ps. chlororaphis 449 with VOCs emitted by cells of IC1270, B-4117 or 449 itself, or with DMDS, leads to significant suppression of transcription of AHL synthase genes phzI and csaI. Thus, along with AHLs, bacterial volatiles might be considered another type of signal molecule involved in microbial communication in the rhizosphere.