title: Low-intensity red and infrared laser effects at high fluences on Escherichia coli cultures.
abstract: Semiconductor laser devices are readily available and practical radiation sources providing wavelength tenability and high monochromaticity. Low-intensity red and near-infrared lasers are considered safe for use in clinical applications. However, adverse effects can occur via free radical generation, and the biological effects of these lasers from unusually high fluences or high doses have not yet been evaluated. Here, we evaluated the survival, filamentation induction and morphology of Escherichia coli cells deficient in repair of oxidative DNA lesions when exposed to low-intensity red and infrared lasers at unusually high fluences. Cultures of wild-type (AB1157), endonuclease III-deficient (JW1625-1), and endonuclease IV-deficient (JW2146-1) E. coli, in exponential and stationary growth phases, were exposed to red and infrared lasers (0, 250, 500, and 1000 J/cm2) to evaluate their survival rates, filamentation phenotype induction and cell morphologies. The results showed that low-intensity red and infrared lasers at high fluences are lethal, induce a filamentation phenotype, and alter the morphology of the E. coli cells. Low-intensity red and infrared lasers have potential to induce adverse effects on cells, whether used at unusually high fluences, or at high doses. Hence, there is a need to reinforce the importance of accurate dosimetry in therapeutic protocols.
authors.affiliation: Departamento de Biofísica e Biometria, Instituto de Biologia Roberto Alcântara Gomes, Rio de Janeiro, RJ, BR.
authors.forename: L L
authors.initials: LL
authors.lastname: Barboza
authors.affiliation: Departamento de Biofísica e Biometria, Instituto de Biologia Roberto Alcântara Gomes, Rio de Janeiro, RJ, BR.
authors.forename: V M A
authors.initials: VM
authors.lastname: Campos
authors.affiliation: Departamento de Biofísica e Biometria, Instituto de Biologia Roberto Alcântara Gomes, Rio de Janeiro, RJ, BR.
authors.forename: L A G
authors.initials: LA
authors.lastname: Magalhães
authors.affiliation: Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Juiz de Fora, Juiz de Fora, MG, BR.
authors.forename: F
authors.initials: F
authors.lastname: Paoli
authors.affiliation: Departamento de Biofísica e Biometria, Instituto de Biologia Roberto Alcântara Gomes, Rio de Janeiro, RJ, BR.
authors.forename: A S
authors.initials: AS
authors.lastname: Fonseca
mesh_terms: D004249:DNA Damage / Q000502:physiology; D004269:DNA, Bacterial / Q000528:radiation effects*; D004926:Escherichia coli / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects*; D007259:Infrared Rays / Q000009:adverse effects* / Q000145:classification; D028022:Low-Level Light Therapy / Q000379:methods*
chemical_list: D004269:DNA, Bacterial