| Summary: |
Molinate is a systemic thiocarbamate herbicide used worldwide to control weeds in rice paddies. The development of strategies to cleanup molinate contaminated sites and to prevent future contaminations is important, because the deliberate application of the herbicide on rice fields promotes its dissemination through the surrounding environment (air, surface and underground water, soil and biotic community), in concentrations that exceed the legal upper values. Bioremediation processes are effective alternatives to costly traditional physicochemical techniques to treat agricultural/industrial contaminated soils and waters. Thus, several authors reported the isolation of microorganisms capable of molinate degradation. However, these isolates transformed molinate into partially oxidized products, as molinate-sulfoxide, that were more persistent and toxic than the parent form. The proponent team isolated a bacterial mixed culture able to degrade molinate through a new metabolic pathway. This mixed culture is the only biological system so far described as being able to mineralize molinate without the accumulation of degradation products. Molinate mineralization is achieved, at least, by the cooperation of Gulosibacter molinativorax ON4T, a new genus and new species of Actinobacteria described by us, and Pseudomonas chlororaphis ON1. G. molinativorax ON4T cleaves the thioester bond of molinate, releasing ethanethiol and a new metabolite identified as azepane-1-carboxylic acid (ACA). G. molinativorax ON4T grows, in pure culture, at the expenses of ACA, while ethanethiol accumulates in the medium. This sulphur compound is toxic for G. molinativorax ON4T, and molinate mineralization is achieved only when Pseudomonas chlororaphis ON1, capable to degrading ethanethiol and ACA, is present.
In this project it is aimed to characterize, at the molecular level, these new catabolic association of molinate degradation. The identification and characterization of the enzymes and g  |
Summary
Molinate is a systemic thiocarbamate herbicide used worldwide to control weeds in rice paddies. The development of strategies to cleanup molinate contaminated sites and to prevent future contaminations is important, because the deliberate application of the herbicide on rice fields promotes its dissemination through the surrounding environment (air, surface and underground water, soil and biotic community), in concentrations that exceed the legal upper values. Bioremediation processes are effective alternatives to costly traditional physicochemical techniques to treat agricultural/industrial contaminated soils and waters. Thus, several authors reported the isolation of microorganisms capable of molinate degradation. However, these isolates transformed molinate into partially oxidized products, as molinate-sulfoxide, that were more persistent and toxic than the parent form. The proponent team isolated a bacterial mixed culture able to degrade molinate through a new metabolic pathway. This mixed culture is the only biological system so far described as being able to mineralize molinate without the accumulation of degradation products. Molinate mineralization is achieved, at least, by the cooperation of Gulosibacter molinativorax ON4T, a new genus and new species of Actinobacteria described by us, and Pseudomonas chlororaphis ON1. G. molinativorax ON4T cleaves the thioester bond of molinate, releasing ethanethiol and a new metabolite identified as azepane-1-carboxylic acid (ACA). G. molinativorax ON4T grows, in pure culture, at the expenses of ACA, while ethanethiol accumulates in the medium. This sulphur compound is toxic for G. molinativorax ON4T, and molinate mineralization is achieved only when Pseudomonas chlororaphis ON1, capable to degrading ethanethiol and ACA, is present.
In this project it is aimed to characterize, at the molecular level, these new catabolic association of molinate degradation. The identification and characterization of the enzymes and genes responsible for molinate breakdown are the major focus of this proposal. |