Bioprospecção de bactérias degradadoras de agrotóxicos em estuário do Rio Jaguaribe (Ceará, Brasil)

Abstract

The indiscriminate use of pesticides causes damage to the environment and human health as a result of itstoxicity. An alternative to mitigate the impacts of pesticidesisthe biodegradation of these substances by bacteria. The objective of this research wasto select potentially pesticide-degrading bacteria isolated fromthe estuary of Jaguaribe River, semiarid of Ceará state. Three collections were carried out atthree points previously established according to salinity gradient (fresh, brackish and salt water). In each point were collected water and sedimentsamples. The bacterialstrains were inoculated onto conventional culture mediumand culture medium added by mix of pesticides picloran, metil parathion and atrazine. Thisdifferentiation media was used to observe the influence of the presence of selective substance (pesticide mix) on the count of total cultivable bacteria. Then, the bacteria were isolated, quantified, identified and submitted to antimicrobialsusceptibility test and plasmid curing. The bacterial counts were ranged of 18,6 x 102 a >250 x 106 UFC.mL-1 est. for water samples, 180 x 101 a 159,5 x 103 UFC.g-1 for controlsedimentsamples and 145 x 101 a >250 x 106UFC.g-1 est. for sedimentsamples onto pesticide mix culture medium. Among the strains, 67% were Gram-positive bacteria, while 37% Gram-negative. Of the totalstrains, 86% were identified until genus and 14% until phylum. Furthermore, 61% of strains were resistantto one or more antibiotics and a largest profile was observed resistance to penicillin and ampicillin. Of the strain subjected to plasmid curing, 61% had potentially chromosomalresistance and 19% had plasmid-mediated resistance. The resultsshowed that was possible to isolate potentially degrading-bacteria. Also, from an ecological point of view, the equivalence found among the total population and pesticide-degrading bacteria in the estuary of the river Jaguaribe is an important factor, indicating thatthe presence of polluting chemicals hasexerted a selective pressure on the localmicrobial community.