Study of the efficiency of biodegradation processes of organic pollutants by endosymbiotic micro-organisms of the insect Diabrotica speciosa and its impact on the acquisition of resistance against insecticides

Abstract

Decades ago, agrochemicals were introduced with the aim of increasing agricultural yields and the control of insects and weeds. Due to the adaptation and resistance developed by these pests, each year greater quantities of pesticide are consumed and/or greater is the need for new protection compounds. However, these practices have caused undesirable effects of environmental contamination. Direct impacts have been observed on soils, waters, foods, and indirectly on mankind itself. As a result, there is an increase in the cost of food production, bioaccumulation and biomagnification of harmful molecules in the environment. Governmental agencies have limited or prohibited the use of various pesticides, trade barriers, etc. However, conventional pesticides are still needed for food production on a large scale. Therefore, through coordinated action it is necessary to propose new techniques for biodegradation of harmful molecules and/or bioremediation of already contaminated areas, minimizing environmental impacts. The highlight of this project are the studies on the interaction between pest insects and endosymbiotic micro-organisms. Insects are the most successful organisms on earth, in part because of their ability to feed from a wide variety of diets. Many of these diets have nutritional deficiencies that to some extent may be supplied by micro-organisms. Thus, there is a strong symbiosis interaction among pest insects, their gastrointestinal micro-organisms and their food preferences. Not only are several micro-organisms involved in processing the food of insects, but they are also part of the detoxification system of the plant material, insect defense against invading pathogens, parasitoids attack and, most recently, the acquisition of resistance of the insects against conventional insecticides. Micro-organisms are able to produce several enzymes which may be applied to promoting the biodegradation of organic products. Furthermore, microbial biodegradation processes are generally regarded as safe and effective at removing pesticides. In this sense, the main focus of this project is to evaluate the potential of endosymbiotic micro-organisms to degrade Persistent Organic Pollutants (POPs), intentionally or not, introduced into soil and water, e.g., dioxins and other insecticides. Indirectly, the project intended to evaluate the performance of symbiotic gastrointestinal micro-organisms of horizontal or vertical transmission in both the acquisition of resistance of pest insects against pesticides and their potential for bioremediation process applications. Diabrotica speciosa is the model insect for this study. The project herein intends to develop a multidisciplinary initiative, forging the chemical ecology, natural product chemistry, microbiology and analytical instrumentation in order to integrate actions to understanding the interactions between pest insects and endosymbiotic micro-organisms. The phases of the project are: to isolate and to characterize the endosymbiotic micro-organisms of D. speciosa, to develop bioreactors for the POPs degradation, kinetic studies of degradation, the identification of biotransformed metabolites, optimization of analytical extraction, pretreatment, instrumental, validation etc. Finally (Last but not least), this work plan attempts at actions and visibility about the suitable management of POPs, thus consolidating the Brazilian and Canadian commitment with the participatory and dynamic implementation of the Stockholm Convention. (AU)