Castro-Díaz, Zenaida

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    Detection of integron-encoded integrases in environments with moderate anthropogenic impact from Puerto Rico
    (2012) Castro-Díaz, Zenaida; Montalvo-Rodríguez, Rafael R.; College of Arts and Sciences - Sciences; Rodríguez Minguela, Carlos; Santos Flores, Carlos; Diffoot Carlo, Nannette; Department of Biology; Román Pérez, Rosa I.
    Integrons are genetic elements with a site-specific recombination system which includes an integrase (IntI) capable of capturing and expressing promoterless, circular DNA molecules known as gene cassettes. Although integrons were initially discovered as elements involved in the transfer of multiple antibiotic resistance mechanisms within the clinical scene, their presence has been increasingly reported in environments with other integrated adaptative traits unrelated to antibiotic resistance functions. This project explores the presence of integrons in microbial communities from environments with moderate anthropogenic impacts in Puerto Rico. These include two extreme environments: hypersaline waters from Cabo Rojo and the Coamo Thermal Springs and soil from the Culebrones Cave in Arecibo. Samples from these places were analyzed to determine the presence of integrases by culture-dependent and culture-independent techniques. Metagenomic DNA was analyzed with an int-targeted PCR assay using degenerate primers. Alignments were performed for all sequences recovered and their relationship with oth- er tyrosine recombinases was analyzed. Sequences were also compared against functional inte- grases for their characterization. Important motifs characteristic of the tyrosine recombinase fam- ily such as: Patch (II and III) and Box (I and II) were detected. Twenty eight novel integrase sequences were recovered from metagenomic DNA extracted from hypersaline water and thirty integron integrases from cave soil. Additionally, eight new integron−encoded integrases were recovered from the Coamo Thermal Springs. Furthermore, integrase genes similar to integrase class 2 that do not contain the premature stop codon X179 were detected by PCR in two halo- philic isolates closely related to the genera Salinivibrio (γ-Proteobacteria) and Bacillus. One isolate from the Coamo Thermal Springs related to the genus Geobacillus showed integrase genes similar to integrase class 1. This study provides the first evidence of the presence of integrase integrons among the microbial community found in environments with moderate anthro- pogenic impacts from Puerto Rico and in the Caribbean. The results obtained also support the argument that the integron-based mechanism for horizontal gene transfer is widespread and can take place in solar saltern ponds, Coamo Thermal Springs and cave soil.