IBBM   21076
INSTITUTO DE BIOTECNOLOGIA Y BIOLOGIA MOLECULAR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Identification and molecular characterization of class 1 integrons in plasmid ?carrying bacterial isolates recovered from a biopurification system used for pesticide removal
Autor/es:
VIETA M. P.; MARTINI M. C.; QUIROGA M. P.; CENTRÓN D.; LAGARES A.; DEL PAPA M. F.
Lugar:
Córdoba
Reunión:
Congreso; XI SAMIGE, Córdoba, Argentina. 5 al 7 de agosto de 2015; 2015
Resumen:
Antecedentes. Los sistemas de biopurificación (BPSs: BioPurification Systems), se han implementado y utilizado eficientemente en la decontaminación de las aguas residuales provenientes del lavado de equipos de pulverización, derrames o fugas durante la carga, mezcla o vaciado de pesticidas en áreas agrícolas. Los BPS son excavaciones o contenedores que contienen una matriz biológicamente activa, llamada biomezcla, en los cuales la remoción de pesticidas ocurre por absorción y biodegradación. Son de composición variable, pero generalmente contienen una mezcla de suelo, materiales lignocelulíticos y otros sustratos orgánicos mezclados en distintas proporciones. En la primera parte de mi trabajo de Tesis Doctoral, he trabajado en la obtención y caracterización de una colección de aislamientos bacterianos portadores de plásmidos de alto peso molecular presentes en un BPS contaminado con más de 30 pesticidas. Los plásmidos de estos aislamientos fueron además secuenciados y analizados in sílico. En el último año de trabajo, Recently, we have isolated and characterized a collection of 35 plasmid-carrying bacterial isolates recovered from a BPS contaminated with more than 50 different pesticides. These cultivable bacteria were selected using a plasmid-screening based method, in order to study the role of plasmids in such environment. It is well known that mobile genetic elements (MGEs) play an essential role in the evolution and adaptation of bacteria as they encode accessory genes that increase bacterial fitness in a given environment.In order to go deeper in the analysis of MGEs, we decided to expand our study looking for the presence of type 1 integrons, which have been found in plasmid backbones. Integrons are assembly platforms that incorporate exogenous open reading frames harbouring attC sites by site-specific recombination and convert them to functional gene cassettes by ensuring their correct expression. In particular, class 1 integrons are widely distributed in the clinical setting as well as in natural environments. Their ability to acquire, exchange, and express antimicrobial resistance gene cassettes, makes them an important MGE to be studied.Objectives. The aim of this work was to investigate the presence of class 1 integrons as well as their genetic content, in a plasmid-containing bacteria collection obtained from a model on-farm biofilter used for wastewater decontamination in intensive agricultural production.Results. In order to evaluate the presence of class 1 integrons, we performed a PCR-based screening for detection of the integrase of type 1 (intI1) . Out of the screened isolates, 23% were positives for intI1, thus suggesting the presence of class 1 integrons in the collection. In a second step, we investigated the presence of genes that frequently constitute the 3´conserved fragment in this type of integrons. The screening revealed that all isolates that contain the intI1 gene posses also the sul1 and qacE genes, wich confer resistance to sulfonamides and quaternary ammonium compounds, respectively. Besides, 4 of these isolates were positive for qacEΔ1, a qacE gene variant.In order to go deeper in the integron characterization, a second PCR-based screening was performed using primers that bind to the 5´and 3´conserved fragments, flanking the variable region. Out of the 8 integron-containing isolates, 3 of them gave a PCR fragment whose sequencing and analysis revealed the presence of a adenylyltransferase gene, which in all cases confers resistance to streptomycin.The analysis of MGE in soil bacteria is a critical issue for improving our current understanding of the mechanisms underlying microbial-genome dynamics.