Metagenômica da degradação da atrazina em solo sob diferentes manejos agrícolas e floresta semidecidual

Abstract

Crop productivity is associated with heavy agrochemical use, one of which is atrazine, broadly applied in Brazil but prohibited in many countries due to negative connotations associated with its toxicity and persistence in the environment. One proposed method to dealing with this compound contamination is through bioremediation, which consists of directly applying microorganisms capable of degrading the compound. These microorganisms (which occur naturally in contaminated environments) can be known and described by the application of metagenomics, which consists of direct sequencing of genomic DNA from the environment and does not rely on cultivation of the microorganisms to do so. Thus, soils under four distinct managements (no management; conventional tillage; no-tillage; continuous grazing and croplivestock integration) and of local semidecidual forest was sampled and sequenced with Illumina technology. About 240 thousand sequences were aligned with BlastAll software against a reference bank of 767 curated genes related to atrazine biodegradation, obtained from the secondary database Uniprot. The alignment output was organized in a SQL relational database, which was consulted for organizing the aligned genes and taxa. The data was then imported to a metagenomics software package, MEGAN, which generated a UPGMA cluster analysis tree. Lastly, the data was also imported in the statistical and graphical package STAMP, which is able to differentiate the superabundant microorganisms between samples, with statistical significance, and generating a principal component analysis (PCA). We were able to find the atrazine degradation genes in every sample. These genes were found in different proportions for the samples with and without the application of atrazine, including in the soil under semidecidual forest. It was possible to define 56 unique bacterial and archaeal genera and 178 species, of which 43 were found to be common to every sample. The soil without management (semidecidual forest) presented the most number of superabundant statistically significant taxa then the other four samples. Every soil contained all atrazine degradation genes in analysis, except for the gene gatA, which occurred only in the crop-livestock integration management sample. The semidecidual forest soil showed superabundant genera, even without history of atrazine application. From this new information, we hope to contribute to future bioprospecting studies with potential application in future studies about the bioprospection of microorganisms with potential to the bioremediation of environments contaminated with atrazine.