Bioprospecção e avaliação do potencial biotecnológico de bactérias degradadoras de agrotóxicos isoladas do Rio Pacotí - CE

Abstract

The intensification of agricultural activities, which aim at food production, is directly related to the increase in human population. In the agro-industrial model in place, pesticides play an important role in increasing productivity. However, the indiscriminate use of these substances has generated social, economical and environmental damages. The launch of pesticides affects all the environmental compartments (air, soil and water), the quality of these resources, and pose risks for their toxicity and ability to bioaccumulate in the food chain. The Pacotí River, which is the major water source for the metropolitan region of Fortaleza, is one of the final destinations of agrochemicals used in Ceará (Atrazine, Methyl- parathion, Picloran, Chlorpyrifos, and others).The knowledge of microbiota and its effect on pesticides is an important step in the search for alternatives to mitigate the damage caused to the environment. Given the reasons above, the aim of this work was to isolate, select and characterize bacterial strains with tolerance and/or potential for degradation of pesticides occurring in Pacotí River. Three water samples were collected at three different points along the river following a salinity gradient (fresh water, brackish water and salt water). The samples went through a selection of microorganisms; later being inoculated in a culture media (Plate Count Agar) that was supplemented with 50 ppm of pesticides cocktail. Potentially degrading bacteria of the pesticides in samples were counted with isolation of colonies, taking into account their morphology, size and presence of pigments. After isolation, the bacterial cultures were subjected to purification and biochemical tests for identification and testing efficiency against pesticides. The tests were made from the Minimum Inhibitory Concentration (MIC) followed by Minimum Bactericidal Concentration (MBC) test. The brackish water showed higher average colony forming units (CFU) ofotentially degrading bacteria per milliliter of water. The majority (73%) of the bacteria isolates proved to be efficient to use the pesticide as a source of carbon, value obtained even at high concentrations of these substances (100 to 200 ppm). Some isolates began to exhibit a characteristic bioluminescence when exposed to pesticides. Salinity was a key environmental factor in the abundance of bacteria in the estuary of the River Pacoti. Chlorpyrifos presented individually, the highest rate of bacterial degradability among the tested substances while Picloran was the most toxic to bacteria.