title: Diversity of gene cassettes and the abundance of the class 1 integron-integrase gene in sediment polluted by metals.
abstract: The integron-gene cassette system has typically been associated with antibiotic-resistant pathogens. However, the diversity of gene cassettes and the abundance of class 1 integrons outside of the clinical context are not fully explored. Primers targeting the conserved segments of attC recombination sites were used to amplify gene cassettes from the sediment of the Mina stream, which exhibited a higher degree of stress to metal pollution in the dry season than the rainy season. Of the 143 total analyzed sequences, 101 had no matches to proteins in the database, where cassette open reading frames could be identified by homology with database entries. There was a predominance of sequences encoding essential cellular functions. Each season that was sampled yielded a specific pool of gene cassettes. Real-time PCR revealed that 8.5 and 41.6 % of bacterial cells potentially harbored a class 1 integron in the rainy and dry seasons, respectively. In summary, our findings demonstrate that most of the gene cassettes have no ascribable function and, apparently, historically metal-contaminated sediment favors the maintenance of bacteria containing the intI1 gene. Thus, the diversity of gene cassettes is far from being fully explored deserving further attention.
authors.affiliation: Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil.
authors.forename: Clarisse
authors.initials: C
authors.lastname: Oliveira-Pinto
authors.affiliation: Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil.
authors.forename: Patrícia S
authors.initials: PS
authors.lastname: Costa
authors.affiliation: Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil.
authors.forename: Mariana P
authors.initials: MP
authors.lastname: Reis
authors.affiliation: Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil.
authors.forename: Edmar
authors.initials: E
authors.lastname: Chartone-Souza
authors.affiliation: Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil. amaral@ufmg.br.
authors.forename: Andréa M A
authors.initials: AM
authors.lastname: Nascimento
mesh_terms: D001151:Arsenic / Q000032:analysis; D041963:Bacteroidetes / Q000235:genetics / Q000302:isolation & purification; D004787:Environmental Pollution; D005798:Genes, Bacterial; D014644:Genetic Variation; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D019426:Integrases / Q000235:genetics*; D007501:Iron / Q000032:analysis; D064307:Microbiota; D020560:Proteobacteria / Q000235:genetics / Q000302:isolation & purification
chemical_list: D007501:Iron; D019426:Integrases; C115006:integron integrase IntI1; D001151:Arsenic
keywords: Arsenic; Class 1 integron; Freshwater sediment; Gene cassette; Iron; Metal; intI gene; qPCR