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A combined physiological and biophysical approach to understand the ligand-dependent efficiency of 3-hydroxy-4-pyridinone Fe-chelates

Publication . Santos, Carla S.; Leite, Andreia; Vinhas, Sílvia; Ferreira, Sofia; Moniz, Tânia; Vasconcelos, Marta W.; Rangel, Maria da Conceição

Ligands of the 3‐hydroxy‐4‐pyridinone (3,4‐HPO) class were considered eligible to formulate new Fe fertilizers for Iron Deficiency Chlorosis (IDC). Soybean (Glycine max L.) plants grown in hydroponic conditions and supplemented with Fe‐chelate [Fe(mpp)3] were significantly greener, had increased biomass, and were able to translocate more iron from the roots to the shoots than those supplemented with an equal amount of the commercially available chelate [FeEDDHA]. To understand the influence of the structure of 3,4‐HPO ligand on the role of the Fe‐chelate to improve Fe‐uptake, we investigated and report here the effect of Fe‐chelates ([Fe(mpp)3], [Fe(dmpp)3], and [Fe(etpp)3]) in addressing IDC. Chlorosis development was assessed by measurement of morphological parameters, quantification of chlorophyll and Fe, and other micronutrient contents, as well as measurement of enzymatic activity (FCR) and gene expression (FRO2, IRT1, and Ferritin). All [Fe(3,4‐HPO)3] chelates were able to provide Fe to plants and prevent IDC but with a different efficiency depending on the ligand. We hypothesize that this may be related with the distinct physicochemical characteristics of ligands and complexes, namely, the diverse hydrophilic–lipophilic balance of the three chelates. To test the hypothesis, we performed an EPR biophysical study using liposomes prepared from a soybean (Glycine3 max L.) lipid extract and spin probes. The results showed that the most effective chelate [Fe(mpp)3] shows a preferential location close to the surface while the others prefer the hydrophobic region inside the bilayer.

2020-08-16Journal article

Open access

A review of Pinaceae resistance mechanisms against needle and shoot pathogens with a focus on the Dothistroma–Pinus interaction

Publication . Fraser, S.; Martın-Garcıa, J.; Perry, A.; Kabir, M. S.; Owen, T.; Solla, A.; Brown, A. V.; Bulman, L. S.; Barnes, I.; Hale, M. D.; Vasconcelos, Marta W.; Lewis, K. J.; Dogmus-Lehtijarvi, H. T.; Markovskaja, S.; Woodward, S.; Bradshaw, R. E.

Dothistroma needle blight (DNB), caused by Dothistroma septosporum and Dothistroma pini, is a highly damaging disease of pine. DNB was originally considered a problem on exotic Pinus radiata plantations in the Southern Hemisphere and on both exotic and native pines in parts of North America in the 1960s. Since the mid-1990s, however, DNB has increased in importance in various parts of the world, including Europe. On susceptible species, DNB causes premature needle drop, a loss of yield and, in some circumstances, mortality. In some areas, DNB is controlled by the application of copper-based fungicides and silvicultural techniques, such as thinning and pruning. In New Zealand, there has also been a long history of selection of more resistant P. radiata for use in breeding programmes. A richer understanding of the resistance mechanisms involved in the Dothistroma–Pinus interaction will play a critical role in helping the development of sustainable integrated DNB management strategies. This review therefore summarizes current knowledge of defence mechanisms involved in the defence of Pinaceae against needle and shoot pathogens and identifies research gaps. Collaborative research efforts from countries directly or indirectly affected by DNB are rapidly generating new knowledge to address these gaps.

2016Journal article

Open access

Enantiomeric fraction evaluation of pharmaceuticals in environmental matrices by liquid chromatography-tandem mass spectrometry

Publication . Ribeiro, Ana Rita; Santos, Lúcia H. M. L. M.; Maia, Alexandra S.; Delerue-Matos, Cristina; Castro, Paula M. L.; Tiritan, Maria Elizabeth

The interest for environmental fate assessment of chiral pharmaceuticals is increasing and enantioselective analytical methods are mandatory. This study presents an enantioselective analytical method for the quantification of seven pairs of enantiomers of pharmaceuticals and a pair of a metabolite. The selected chiral pharmaceuticals belong to three different therapeutic classes, namely selective serotonin reuptake inhibitors (venlafaxine, fluoxetine and its metabolite norfluoxetine), beta-blockers (alprenolol, bisoprolol, metoprolol, propranolol) and a beta2-adrenergic agonist (salbutamol). The analytical method was based on solid phase extraction followed by liquid chromatography tandem mass spectrometry with a triple quadrupole analyser. Briefly, Oasis® MCX cartridges were used to preconcentrate 250 mL of water samples and the reconstituted extracts were analysed with a Chirobiotic™ V under reversed mode. The effluent of a laboratory-scale aerobic granular sludge sequencing batch reactor (AGS-SBR) was used to validate the method. Linearity (r2 > 0.99), selectivity and sensitivity were achieved in the range of 20–400 ng L−1 for all enantiomers, except for norfluoxetine enantiomers which range covered 30–400 ng L−1. The method detection limits were between 0.65 and 11.5 ng L−1 and the method quantification limits were between 1.98 and 19.7 ng L−1. The identity of all enantiomers was confirmed using two MS/MS transitions and its ion ratios, according to European Commission Decision 2002/657/EC. This method was successfully applied to evaluate effluents of wastewater treatment plants (WWTP) in Portugal. Venlafaxine and fluoxetine were quantified as non-racemic mixtures (enantiomeric fraction ≠ 0.5). The enantioselective validated method was able to monitor chiral pharmaceuticals in WWTP effluents and has potential to assess the enantioselective biodegradation in bioreactors. Further application in environmental matrices as surface and estuarine waters can be exploited.

2014Journal article

Restricted access

Bacterial degradation of moxifloxacin in the presence of acetate as a bulk substrate

Publication . Carvalho, M. F.; Maia, A. S.; Tiritan, M. E.; Castro, P. M. L.

Fluoroquinolones constitute a group of emerging pollutants and their occurrence in different environmental compartments is becoming object of increasing public concern due to their ecotoxicological effects and the potential to develop resistant bacteria. This study aimed to investigate the biodegradation of moxifloxacin (MOX), for which studies in the literature are very scarce. An activated sludge (AS) consortium and three bacterial strains able to degrade fluoroaromatic compounds e strains F11, FP1 and S2 e were tested. Biodegradation studies were conducted using acetate as a bulk carbon source. Strain F11 showed the highest biodegradation capacity, being able to completely consume and dehalogenate 7.5 mM of the target antibiotic when daily co-supplemented with acetate present as a readily degradable organic substrate in wastewaters. MOX could be used by strain F11 as a sole nitrogen source but the presence of an external nitrogen source in the culture medium was essential for complete biodegradation. Strain F11 was capable of completely consuming MOX in a range between 2 and 11 mM, although stoichiometric fluoride release was not obtained for the highest tested concentration. The antibacterial activity of residual MOX and of the metabolic products potentially resultant from the biodegradation process was investigated by agar diffusion tests, demonstrating that MOX biodegradation is associated with the elimination of the antibacterial properties of the target antibiotic and of the produced metabolites, which is an important result, as the activity of antibiotics and/or their metabolites in the environment, even at low levels, may lead to the development of resistant bacterial strains. Overall, the results obtained in this study suggest that strain F11 is a promising microorganism for the treatment of waters contaminated with MOX, where it could be used for bioaugmentation/bioremediation purposes. To the best of our knowledge, this is the first study reporting complete removal and dehalogenation of MOX by a single microorganism.

2016Journal article

Restricted access

Characterization of clinical and food Listeria monocytogenes isolates with different antibiotic resistance patterns through simulated gastrointestinal tract conditions and environmental stresses

Publication . Cunha, S.; Komora, N.; Magalhães, R.; Almeida, Gonçalo; Ferreira, V.; Teixeira, Paula

Thirty-three Listeria monocytogenes isolates previously collected from two sources, food (n = 18) and human patients suffering from listeriosis (n = 15), with variable antibiotic susceptibility profiles (sensitive/resistant) to erythromycin, ciprofloxacin and nitrofurantoin, were studied for their ability to survive (i) the environmental stress provided by sequential conditions that simulate the digestive tract, and (ii) extreme pH values (1.5–12). The results showed a response that was only strain dependent. There were no variability in survival results based on type of stress (low or high pH), source (food or clinical), or sensitivity/resistance to antibiotics (p > 0.01). Some strains of L. monocytogenes are able to survive extreme acid and alkaline conditions, and conditions that mimic the sequential stressors found in the gastro-intestinal tract. The resistance to the antibiotics tested in this study by some L. monocytogenes strains did not confer any cross-protection to acid or alkaline stressors.

2016Journal article

Restricted access