Microbial degradation of the herbicide molinate by defined cultures and in the environment

Abstract

Molinate is a thiocarbamate herbicide used worldwide in rice crop protection. As with other pesticides, molinate is a recognized environmental pollutant, detected in soils, irrigation water, or rivers and bio-accumulated by some wildlife forms. For this reason, and in spite of its low toxicity to humans, environmental protection measures, which include reduction of use and/or remediation processes, are recommended. Due to its physic-chemical properties, molinate can easily disperse and react in the environment, originating diverse transformation products, some with increased toxicity. In spite of being a xenobiotic compound, molinate can also suffer microbial transformation by bacteria or fungi, sometimes serving as nutrient and energy source. In an attempt to isolate microorganisms to be used in the bioremediation of molinate-contaminated sites, a mixed culture, dominated by the actinobacterium Gulosibacter molinativorax ON4(T), was recovered from the runoff of a molinate-producing plant. Beyond a promising tool to decontaminate molinate-polluted sites, this culture also brought interesting insights into the biology of the degradation of this herbicide. In this review, an overview of the distribution and properties of molinate as environmental contaminant, the capability of microorganisms to transform this herbicide, and some reflections about possible bioremediation approaches are made.

The Fate of Organophosphorus Pesticides during Camellia Oil Production

“…When being sprayed on crops, pesticide is subject to photodegradation, microbial, and chemical degradation reactions (Nunes and others ). Although some degradation products (metabolite) of the pesticides could be less toxic and harmless, it is not uncommon for them to be more toxic than the parent pesticides.…”

Potential roles for microbial endophytes in herbicide tolerance in plants

“…For example, organophosphorus compounds such as glyphosate (Table ), accounting for a third of worldwide pesticide sales, can be degraded by multiple documented pathways by microbes in the rhizosphere . Similarly, the thiocarbamate herbicide molinate is degraded by multiple pathways in both bacterial and fungal species, depending on environmental conditions . Under aerobic conditions, the majority of molinate is degraded by oxidative routes in the presence of an additional cometabolic carbon source.…”

“…Under aerobic conditions, the majority of molinate is degraded by oxidative routes in the presence of an additional cometabolic carbon source. However, under anaerobic conditions, complete mineralisation of molinate as a single carbon and energy source has been attributed to a hydrolytic mechanism …”

“…9 Similarly, the thiocarbamate herbicide molinate is degraded by multiple pathways in both bacterial and fungal species, depending on environmental conditions. 13 Under aerobic conditions, the majority of molinate is degraded by oxidative routes in the presence of an additional cometabolic carbon source. However, under anaerobic conditions, complete mineralisation of molinate as a single carbon and energy source has been attributed to a hydrolytic mechanism.…”

“…However, under anaerobic conditions, complete mineralisation of molinate as a single carbon and energy source has been attributed to a hydrolytic mechanism. 13 While removal of chemical residues from the environment has many positive features, the microbial degradation of pre-emergence herbicides in the soil can ultimately regulate their activity in weed control applications. For example, when applied to the soil, 2,4-D is known to have a short half-life on account of complete microbial degradation.…”