Búsqueda y caracterización molecular de integrones tipo 1 presentes en bacterias aisladas de un biofiltro utilizado para la decontaminación de pesticidas. Nº 2015-5-435

VIETA MP; MARTINI MC; QUIROGA M.P.; CENTRON D; LAGARES A; DEL PAPA MF

Córdoba

Congreso; XI Congreso Argentino de Microbiología General SAMIGE; 2015

SAMIGE

Biopurification systems (BPS) are complex soil-relatedand artificially-generated environments usually designed for the removal oftoxic compounds from polluted wastewater sources. BPS receives high loads ofpesticides and other toxic compounds, thus imposing   a  strong,   constant   and  long-term   selective   pressure  on   the   evolution  and   growth   of  the   associated microbiome.Recently, we have isolated and characterized a collection of 35plasmid-carrying bacterial isolates recovered from a BPS contaminated with morethan 50 different pesticides. These cultivable bacteria were selected using aplasmid-screening based method, in order to study the role of plasmids in suchenvironment. It is well known that mobile genetic elements (MGEs) play anessential role in the evolution and adaptation of bacteria as they encodeaccessory genes that increase bacterial fitness in a given environment. Inorder to go deeper in the analysis of MGEs, we decided to expand our studylooking for the presence of type 1 integrons, which have been found in plasmidbackbones. 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 integronsare 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. The aim of this work was to investigatethe presence of class 1 integrons as well as their genetic content, in aplasmid-containing bacteria collection obtained from a model on-farm biofilterused for wastewater decontamination in intensive  agricultural  production. 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 asecond step, we investigated the presence of genes that frequently constitutethe 3 ́conserved fragment in this type of integrons. The screening revealedthat 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 qacE∆1, a qacE genevariant. In order to go deeper in the integron characterization, a secondPCR-based screening was performed using primers that bind to the 5 ́and 3́conserved fragments, flanking the variable region. Out of the 8integron-containing isolates, 3 of them gave a PCR fragment whose sequencing andanalysis revealed the presence of a adenylyltransferase gene, which in allcases confers resistance to streptomycin. The analysis of MGE in soil bacteriais a critical issue for improving our current understanding of the mechanisms underlyingmicrobial-genome dynamics.