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Thermal springs provide extreme ecological conditions for aquatic communities owing to their high water temperature and particular water chemistry. The thermal springs and their connected watercourses provide a thermal laboratory by offering a wide range of temperatures within short spatial distances. To date, the information on how the biodiversity of these springs is related to water temperature or chemistry is limited. We studied the effects of water temperature on diatom community diversity and structure with the objective to supply a baseline for the conservation of thermal springs. We sampled 31 sites of 16 thermal springs across a temperature gradient between 18.5 and 63.0°C in the north-western Iberian Peninsula and related diatom richness and structure to water temperature. A total of 124 diatom species were identified in springs with water temperature between 18.5 and 42.4°C. Community diversity decreased with increasing temperature and the highest species richness was found at temperatures ≤ 25°C. Three diatom assemblages were defined, discriminated by temperature ranges (≤25°C, 25–35°C and ≥35°C). Water temperature was found to be an important driver of diatom community composition in the thermal systems studied. Temperature affects diatom distribution decreasing diversity with the increase in global water temperature. [ABSTRACT FROM AUTHOR]

Microbial resistance to antibiotics is one of the biggest public health threats of the modern world. Antibiotic resistance is an area of much clinical relevance and therefore research that has the potential to identify agents that may circumvent it or treat resistant infections is paramount. Solution behavior of various fluoroquinolone (FQ) complexes with copper(II) in the presence and absence of 1,10-phenanthroline (phen) was studied in aqueous solution, by potentiometry and/or spectrophotometry, and are herein described. The results obtained showed that under physiological conditions (micromolar concentration range and pH 7.4) only copper(II):FQ:phen ternary complexes are stable. Hence, these complexes were synthesised and characterised by means of UV-visible and IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. In these complexes, the FQ acts as a bidentate ligand that coordinates the metal cation through the carbonyl and carboxyl oxygen atoms and phen coordinates through two N-atoms forming the equatorial plane of a distorted square-pyramidal geometry. The fifth position of the penta-coordinated Cu(II) centre is generally occupied axially by an oxygen atom from a water molecule or from a nitrate ion. Minimum inhibitory concentration (MIC) determinations of the complexes and comparison with free FQ in various E. coli strains indicate that the Cu-complexes are as efficient antimicrobials as the free antibiotic. Moreover, results strongly suggest that the cell intake route of both species is different supporting, therefore, the complexes' suitability as candidates for further biological testing in FQ-resistant microorganisms. [ABSTRACT FROM AUTHOR]

Abstract: Antimicrobial peptides (AMPs) take part in the immune system by mounting a first line of defense against pathogens. Recurrent structural and functional aspects are observed among peptides from different sources, particularly the net cationicity and amphipathicity. However, the membrane seems to be the key determinant of their action, either as the main target of the peptide action or by forming a barrier that must be crossed by peptides to target core metabolic pathways. More importantly, the specificity exhibited by antimicrobial peptides relies on the different lipid composition between pathogen and host cells, likely contributing to their spectrum of activity. Several mechanisms of action have been reported, which may involve membrane permeabilization through the formation of pores, membrane thinning or micellization in a detergent-like way. AMPs may also target intracellular components, such as DNA, enzymes and even organelles. More recently, these peptides have been shown to produce membrane perturbation by formation of specific lipid–peptide domains, lateral phase segregation of zwitterionic from anionic phospholipids and even the formation of non-lamellar lipid phases. To countermeasure their activity, some pathogens were successful in developing effective mechanisms of resistance to decrease their susceptibility to AMPs. The functional and integral knowledge of such interactions and the clarification of the complex interplay between molecular determinants of peptides, the pathogen versus host cells dichotomy and the specific microenvironment in which all these elements convene will contribute to an understanding of some elusive aspects of their action and to rationally design novel therapeutic agents to overcome the current antibiotic resistance issue. [Copyright &y& Elsevier]

Abstract: Diatoms are widely used in stream bioassessment due to their broad distribution, extraordinary variability and the ability to integrate changes in water quality. The indices Specific Polluosensitivity Index (SPI), standardized Biological Diatom Index (BDI), European Economic Community Index (CEC) and Generic Diatom Index (GDI), originally developed in France, are often applied in Portugal to evaluate stream ecological quality based on diatom communities. Alternatively, predictive models resulting from the comparison between the communities of the study site and those of a set of reference sites representing undisturbed or the best available conditions of a given region have been proposed as valuable methods for evaluating the ecological status of streams. In the present study, we applied the four above-mentioned widely used diatom-based indices (SPI, BDI, CEC and GDI) and a predictive model (MoDi) to 54 sites located in central Portugal to assess the sensitivity of the five methods to a range of anthropogenic disturbances cumulatively affecting streams and represented by 27 variables (e.g., organic enrichment, changes in morphology of the channels, integrity of the riparian corridor, land use in the catchment). The results were analyzed comparatively through Spearman correlations, Boxplots and Stepwise Discriminant Analysis. This study confirmed the sensitivity of diatoms to organic and nutrient contamination (showed by the MoDi, BDI, CEC and SPI) and revealed the importance of suspended solids (through the MoDi, GDI, and SPI). The relevance of modifications in land use to diatoms was shown by all methods applied, except for the GDI. The MoDI also revealed the importance of changes in the structure and morphology of the reach and the channel, like the construction of artificial walls or embankments and connectivity; the BDI also related its assessments with the riparian zone integrity; and the SPI was not useful in detecting morphological pressures. The GDI produced the most divergent assessments and was less effective in revealing the anthropogenic disturbances. The use of the predictive model (MoDi) is therefore a good method for the assessment of streams in central Portugal because it expresses a great diversity of quantitative and qualitative changes in freshwater systems reflected in the structure (species richness and abundance) of diatom communities. [Copyright &y& Elsevier]

The thermal unfolding of plastocyanin from the mesophilic cyanobacterium Synechocystis is described herein, and the results are compared with those obtained for the homologous thermophilic protein from Phormidium laminosum. The thermal unfolding is irreversible under all the conditions that were investigated. Plastocyanin from the thermophilic organism, both in the native state and in the apoprotein form, proved to be more thermostable than its mesophilic counterpart under all experimental conditions. Synechocystis reduced plastocyanin has been shown to be more stable than the oxidized species, both with respect to the required temperature for protein unfolding and with respect to the kinetics of the process. This behavior contrasts with that observed for Phormidium plastocyanin, in which the oxidized form is the more stable one. The unfolding pH dependence and kinetic studies indicate that around physiological pH, the most kinetically stable form is also the one more resistant to temperature variations, suggesting a close compromise between function and stability. Molecular dynamics simulations suggest that Phormidium and Synechocystis plastocyanins follow different unfolding pathways that affect different protein areas and which could be responsible for the observed dissimilar thermal resistance. [ABSTRACT FROM AUTHOR]

Predictive models developed to assess water quality in the Mondego River basin (Portugal), based on the BEnthic Assessment of SedimenT (BEAST) model, were compared at three identifications levels: order, family, and genus (species) of macroinvertebrates. Fifty-five reference sites were originally selected for building the model, but this number was reduced to 51 (lowest level), 52 (family), and 53 (order), after the grouping procedures (CLUSTER, MDS, and SIMPER; Primer 5.2.6, Primer-E Ltd., Plymouth, UK). The discriminating variables (stepwise discriminant analysis) stream order, current velocity, pool quality, and substrate quality were common to the genus (species) and family models. Substrate quality was the only discriminating variable of the order model. The model performances, based on their ability to correctly predict reference site membership (complete MDS with jackknifed cross-validation), ranged from 78% (lowest level) to 81% (family and order levels). Twenty test sites were used to compare site assessments using each of the models. We concluded that the lowest-level model of identification provides the best evaluations of water quality assessment and performed well, that the family-level model reacted similarly and could be a good alternative for bioassessment programmes, and that a greater effort toward improving our knowledge of aquatic macroinvertebrates in Portugal is recommended as species are important in assessing water quality. [ABSTRACT FROM AUTHOR]

The thermal unfolding of the plastocyanin from Phormidium laminosum, a thermophilic cyanobacterium, is herein described. The main objective of this work is to identify structural factors responsible for the higher stability observed in proteins from thermophilic organisms. With the aid of fluorescence spectroscopy, EPR, and NMR, the factors influencing the unfolding process of the protein were investigated, and procedures for its study have been standardized. The different spectroscopic techniques used provided consistent results showing that the thermal unfolding of plastocyanin is irreversible under all the conditions investigated and that this irreversibility does not appear to be related to the presence of oxygen. The oxidized plastocyanin species has proven to be more stable than the reduced one, with respect to both the required temperature for protein unfolding (up to a 9 °C difference between the two forms) and the kinetics of the process. The behavior of this plastocyanin contrasts with that of other cupredoxins whose unfolding had previously been studied. The unfolding pH dependence and kinetic studies indicate a process with a tight control around the physiological pH in which plastocyanin plays its redox role and the protein's isoelectric point (5.2), suggesting a close compromise between function and stability. [ABSTRACT FROM AUTHOR]

DNA metabarcoding from the ethanol used to store macroinvertebrate bulk samples is a convenient methodological option in molecular biodiversity assessment and biomonitoring of aquatic ecosystems, as it preserves specimens and reduces problems associated with sample sorting. However, this method may be affected by errors and biases, which need to be thoroughly quantified before it can be mainstreamed into biomonitoring programmes. Here, we used 80 unsorted macroinvertebrate samples collected in Portugal under a Water Framework Directive monitoring programme, to compare community diversity and taxonomic composition metrics estimated through morphotaxonomy versus metabarcoding from storage ethanol using three markers (COI‐M19BR2, 16S‐Inse01 and 18S‐Euka02) and a multimarker approach. A preliminary in silico analysis showed that the three markers were adequate for the target taxa, with detection failures related primarily to the lack of adequate barcodes in public databases. Metabarcoding of ethanol samples retrieved far less taxa per site (alpha diversity) than morphotaxonomy, albeit with smaller differences for COI‐M19BR2 and the multimarker approach, while estimates of taxa turnover (beta diversity) among sites were similar across methods. Using generalized linear mixed models, we found that after controlling for differences in read coverage across samples, the probability of detection of a taxon was positively related to its proportional abundance, and negatively so to the presence of heavily sclerotized exoskeleton (e.g., Coleoptera). Overall, using our experimental protocol with different template dilutions, the COI marker showed the best performance, but we recommend the use of a multimarker approach to detect a wider range of taxa in freshwater macroinvertebrate samples. Further methodological development and optimization efforts are needed to reduce biases associated with body armouring and rarity in some macroinvertebrate taxa. [ABSTRACT FROM AUTHOR]

Investigates the aldehyde oxidoreductase activity in Desulfovibrio alaskensis NCIMB 13491, a strain isolated from a soured oil reservoir in Purdu Bay, Alaska. Oxidation of aldehydes to carboxylic acid form; Reduction of protein with excess dithionite; Crystal structures of homologous enzymes.

Abstract: Solution behavior of lomefloxacin (lmx) complexes with copper(II) in the presence and absence of 1,10-phenanthroline (phen) was studied in aqueous solution, by potentiometry. The results obtained showed that under physiological conditions (micromolar concentration range and pH7.4) only copper(II):lmx:phen ternary complexes are stable. Hence, a novel copper(II) ternary complex of lomefloxacin with the nitrogen donor heterocyclic ligand phen was synthesized and characterized by means of UV–visible and IR spectroscopy, elemental analysis and X-ray crystallography. In the synthesized complex (1), [Cu(lmx)(phen)(NO3)]·5H2O, lmx acts as a bidentate ligand coordinating the metal cation, in its anionic form, through the carbonyl and carboxyl oxygens and phen coordinates through two N-atoms forming the equatorial plane of a distorted square-pyramidal geometry. The fifth ligand of the penta-coordinated Cu(II) center is occupied axially by an oxygen atom from the nitrate ion. Minimum inhibitory concentration (MIC) determinations of the complex and comparison with free lomefloxacin in various E. coli strains indicated that the Cu-complex is an antimicrobial which is as efficient as the free antibiotic but strongly suggest that the cell intake route of both species is different. Moreover, spectrophotometric stability studies suggest that the solution of the complex synthesized is considerably more photostable than the free fluoroquinolone supporting, therefore, the complex's suitability as a candidate for further biological testing in fluoroquinolone-resistant microorganisms with possible reduced side-effects. [Copyright &y& Elsevier]

Antimicrobial peptides (AMPs) from the dermaseptin and phylloseptin families were isolated from the skin secretion of Phyllomedusa nordestina, a recently described amphibian species from Northeastern Brazil. One dermaseptin and three phylloseptins were chosen for solid phase peptide synthesis. The antiprotozoal and antimicrobial activities of the synthetic peptides were determined, as well as their cytotoxicity in mouse peritoneal cells. AMPs are being considered as frameworks for the development of novel drugs inspired by their mechanism of action. [ABSTRACT FROM AUTHOR]

Abstract: Solution behavior of levofloxacin (lvx) complexes with copper(II) in the presence and absence of phen was studied in aqueous solution, by potentiometry. The results obtained show that under physiological conditions (micromolar concentration range and pH 7.4) only copper(II):lvx:phen ternary complexes are stable. Hence, a novel copper(II) ternary complex of fluoroquinolone levofloxacin with nitrogen donor heterocyclic ligand phen was synthesized and characterized by means of UV–Visible and IR spectroscopy, elemental analysis and X-Ray crystallography. In the synthesized complex (1), [Cu(lvx)(phen)(H2O)](NO3).2H2O, levofloxacin acts as a bidentate ligand coordinating to the metal, in its anionic form, through the carbonyl and carboxyl oxygens and phen coordinates through two N-atoms forming the equatorial plane of a distorted square-pyramidal geometry. The fifth ligand of the penta-coordinated Cu(II) centre is occupied axially by an oxygen atom from a water molecule. Minimum inhibitory concentration (MIC) determinations of the complex and comparison with free levofloxacin in various E. coli strains indicated that the Cu-complex is as efficient an antimicrobial as the free antibiotic (both in the case of the dissolved synthesized complex and the complex formed following stoichiometric mixture of the individual components in solution). Moreover, results strongly suggest that the cell intake route of both species is different supporting, therefore, the complex''s suitability as a candidate for further biological testing in fluoroquinolone-resistant microorganisms. [Copyright &y& Elsevier]

Abstract: Solution behaviour of enrofloxacin complexes with copper(II), nickel(II), cobalt(II) and zinc(II) in the presence and absence of 1, 10-phenanthroline was studied in aqueous solution, by potentiometry. The results obtained show that under physiological conditions (micromolar concentration range and pH 7.4) only copper(II) forms stable complexes. Binary copper(II)/enrofloxacin and ternary copper(II)/enrofloxacin/phenanthroline complexes were synthesised and characterized by elemental analysis, UV–visible spectroscopy and FTIR. The antimicrobial activity of these complexes and of copper(II)/enrofloxacin and copper(II)/enrofloxacin/phenanthroline solutions, prepared by mixing of the individual components in the same stoichiometric proportion and concentration range used for the synthesised complexes, was tested against two different Escherichia coli strains. Although, at a glance, the results point to a possible use of both complexes as metalloantibiotics, a detailed analysis shows that, at biological concentrations, the copper(II) binary complex does not exist and the antimicrobial activity observed is a consequence of its dissociation into free enrofloxacin. Consequently, only the ternary complex seems worth pursuing as a possible antimicrobial agent candidate. Moreover, as the biological studies showed, both the synthesised complexes and the solutions prepared by mixing the components exhibited the same behaviour. Hence, a new, faster and accurate methodology to screen metalloantibiotics prior to synthesis of the complexes is proposed. [Copyright &y& Elsevier]