ISOLATION AND IDENTIFICATION OF INDIGENOUS ATRAZINE-DEGRADING BACTERIAL STRAINS FROM BALCARCE, ARGENTINA

BULLÓN, MILAGROS; AMENTA MELINA ; DE GERÓNIMO EDUARDO; PEREZ JONAS; PAGNUSSAT LUCIANA

Congreso; SAIB - SAMIGE Joint meeting 2021 on line; 2021

Agricultural intensification and replacement of conventional tillage (CT) with no till management (NT) -in which weed control is exclusively chemical- has escalated the application of several herbicides. In Argentina, approximately 46% of the agricultural area is under NT, and the excessive pesticide application threatens the sustainability of the soil resource. Atrazine is a selective herbicide for maize and sorghum crops, widely used in Argentina. Extensive use of atrazine resulted in its frequent detection in Buenos Aires province streams. The high levels of atrazine detection in water is of great concern to human health as, through toxicological studies, atrazine has raised as a possible carcinogen, an endocrine disruptor and a teratogenic agent. In recent years, several studies have demonstrated the participation of soil microorganisms in the degradation of S-triazines. The use of microorganisms or other biological agents to recover soil and water has been referred to as ´bioremediation´. However, the main disadvantage for the bioremediation of soils contaminated with s-triazine is the lack of appropriate indigenous microbial strains, adapted to particular soils and environmental conditions were they will be used. The aim of the present work was to isolate and identify indigenous atrazine-degrading microbial strains for future bioremediation purposes. Soil samples were collected from the surface soil layer (0?10 cm) of five agricultural sites with a history of atrazine application from Balcarce, Buenos Aires. To obtain indigenous atrazine-degrading bacteria, an enrichment technique was performed. Briefly, 500 g of soil and kept during 8 months at 28 °C and once a month, atrazine was applied to a final concentration of 0.5 Kg x ha-1. At the end of the atrazine loading period, bacterial strains capable of use atrazine as the only source of carbon and nitrogen were isolated. For the identification of isolated bacterial strains, PCR amplification and sequencing of the 16S RNAs gene was performed. The resulting sequences were deposited in the Genbank database and compared to other sequences available in the database with the NCBI BLAST server (http:// blast.ncbi.nlm.nih.gov/). From 11 isolates, four bacterial strains were identified. Two of the identified strains, Paenibacillus massiliensis and Stenotrophomonas sp. have been reported as plant growth promoting bacteria which is of particular interest for future analysis. Studies are in progress to biochemically characterize the identified strains, for future bioremediation trials.