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Synergic role of the two ars operons in arsenic tolerance in P seudomonas putida KT 2440
Author(s) -
Fernández Matilde,
Udaondo Zulema,
Niqui JoséLuis,
Duque Estrella,
Ramos JuanLuis
Publication year - 2014
Publication title -
environmental microbiology reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.229
H-Index - 69
ISSN - 1758-2229
DOI - 10.1111/1758-2229.12167
Subject(s) - operon , arsenite , arsenic , mutant , arsenate , gene , pseudomonas putida , strain (injury) , genetics , chemistry , biology , microbiology and biotechnology , organic chemistry , anatomy
Summary The chromosome of P seudomonas putida KT 2440 carries two clusters of genes, denoted ars 1 and ars 2 , that are annotated as putative arsenic resistance operons. In this work, we present evidence that both operons encode functional arsenic‐response regulatory genes as well as arsenic extrusion systems that confer resistance to both arsenite [ As ( III )] and arsenate [ As ( V )]. Transcriptional fusions of P ars1 and P ars2 to lacZ revealed that expression of both operons was induced by arsenite and arsenate. We generated single mutants in ars 1 and ars 2 , which showed lower resistance to arsenic than the wild‐type strain. A double ars 1/ ars 2 was found to be highly sensitive to arsenic. Minimum inhibitory concentrations ( MIC s) for single mutants decreased two‐ to fourfold with respect to the parental strain, while in the double mutant the MIC decreased 128‐fold for arsenite and 32‐fold for arsenate. Bioinformatic analysis revealed that the ars 2 resistance operon is part of the core genome of P . putida , while the ars 1 operon appears to only occur in the KT 2440 strain, suggesting that ars 1 was acquired by horizontal gene transfer. The presence of ars 1 in KT 2440 may explain why it exhibits higher resistance to arsenic than other P . putida strains, which bear only the ars 2 operon.