RESUMO
Cyanobacteria are a group of photosynthetic, nitrogen-fixing bacteria present in a wide variety of habitats such as freshwater, marine, and terrestrial ecosystems. In this work, the effects of As(III), a major toxic environmental pollutant, on the lipidomic profiles of two cyanobacteria species (Anabaena and Planktothrix agardhii) were assessed by means of a recently proposed method based on the concept of regions of interest (ROI) in liquid chromatography mass spectroscopy (LC-MS) together with multivariate curve resolution alternating least squares (MCR-ALS). Cyanobacteria were exposed to two concentrations of As(III) for a week, and lipid extracts were analyzed by ultrahigh-performance liquid chromatography/time-of-flight mass spectrometry in full scan mode. The data obtained were compressed by means of the ROI strategy, and the resulting LC-MS data sets were analyzed by the MCR-ALS method. Comparison of profile peak areas resolved by MCR-ALS in control and exposed samples allowed the discrimination of lipids whose concentrations were changed due to As(III) treatment. The tentative identification of these lipids revealed an important reduction of the levels of some galactolipids such as monogalactosyldiacylglycerol, the pigment chlorophyll a and its degradation product, pheophytin a, as well as carotene compounds such as 3-hydroxycarotene and carotene-3,3'-dione, all of these compounds being essential in the photosynthetic process. These results suggested that As(III) induced important changes in the composition of lipids of cyanobacteria, which were able to compromise their energy production processes. Graphical abstract Steps of the proposed LC-MS + MCR-ALS procedure.
Assuntos
Arsênio/metabolismo , Clorofila/metabolismo , Cianobactérias/efeitos dos fármacos , Poluentes Ambientais/metabolismo , Metabolismo dos Lipídeos/efeitos dos fármacos , Anabaena/efeitos dos fármacos , Anabaena/metabolismo , Anabaena/ultraestrutura , Cromatografia Líquida de Alta Pressão/métodos , Cianobactérias/metabolismo , Cianobactérias/ultraestrutura , Análise dos Mínimos Quadrados , Espectrometria de Massas/métodos , Análise MultivariadaRESUMO
Arsenate (As(V)) and arsenite (As(III)) contamination is able to interfere negatively on plant metabolism, promoting a reduction of nutrients uptake and transport and also an increase of reactive oxygen species (ROS) generation. However, some plants are considered tolerant against As exposure through the activation of defense mechanisms. Therefore, this study aimed to evaluate the effects of different As(V) and As(III) concentrations (0.0, 6.6, 13.2, 26.4 and 52.8 µmol L(-1)), on mineral nutrients concentration [calcium (Ca), magnesium (Mg), phosphorous (P), iron (Fe), manganese (Mg) and copper (Cu)], on membrane lipid peroxidation and also on the enzymes belonging to the antioxidant defense system [superoxide dismutase (SOD), total peroxidase (POX), catalase (CAT), glutathione reductase (GR) and ascorbate peroxidase (APX)] of plants of Lactuca sativa L. cv Hanson. As(V) and As(III), showed, in general, the same toxic effects in leaves and roots with significant changes in essential macro- and micronutrients concentration. Lipid peroxidation of cellular membranes was also observed in tested plants, probably resulted from an action of ROS generated by this metalloid. The increase of ROS generation and their scavenge were evident since an increase of SOD, POX, CAT and APX activity in leaves, and SOD, CAT and GR activity in roots were observed. Therefore, As(V) and As(III) exposure resulted in toxic effects in leaves and roots of lettuce plants; however, this plant species was able to attenuate these potential As damages through the activation of defense mechanisms, keeping its metabolism. Arsenic-tolerant plants are considered a great risk to the public health since it results in As insertion to the food chain.