Maria Feio - Academia.edu (original) (raw)

Papers by Maria Feio

Microscopy and Microanalysis, 2013

In this talk the utility of atomic force microscopy (AFM) for research into infectious parasites ... more In this talk the utility of atomic force microscopy (AFM) for research into infectious parasites will be discussed. AFM has grown from relatively recent beginnings to become an extremely powerful technique in the life sciences, coupling high resolution imaging with a range of non-imaging experiments. Importantly, these experiments can be performed in situ, even on individual molecules or on live cells.The two examples discussed relate to the important diseases leishmaniasis and malaria. Leishmaniasis is a disease caused by the protozoan parasite of the Leishmania genera, and causes approximately 60,000 deaths per year. Despite the high death toll, the disease has been the subject of relatively little research and little treatment is available, probably because the most severe cases are confined to developing nations. The most severe form, visceral leishmaniasis is caused by the species known as Leishmania infantum (syn. L. chagasi). A promising new anti-leishmania drug, DS01 has bee...

Journal of the Brazilian Chemical Society, 1997

Realizaram-se estudos electroquímicos sobre a biocorrosão de aço carbono na presença e ausência d... more Realizaram-se estudos electroquímicos sobre a biocorrosão de aço carbono na presença e ausência de bactérias redutoras de sulfato (SRB) em meios aquosos de lactato/sulfato e lactato/nitrato. Medidas de potencial em circuito aberto revelaram um deslocamento do potencial no sentido dos potenciais mais nobres, em ambos os meios. Contudo, oscilações regulares de potencial foram observadas somente no meio de lactato/sulfato. As fotografias de SEM revelaram a presença de pites, distribuídas na superfície das amostras em ambos os meios, com pites de pequeno tamanho e de forma mais uniforme no meio de lactato/sulfato, o que está de acordo com os resultados de potencial em circuito aberto. A voltametria cíclica mostrou claramente que as SRBs em meio de lactato/sulfato originam velocidades de dissolução elevadas na região transpassiva, com formação de espécies Fe 3+. Elec tro chem i cal stud ies of the biocorrosion of mild steel in the pres ence and ab sence of sulfate re duc ing bac te ria (SRB) grown in lac tate/sul fate and lac tate/ni trate aque ous me dia were per formed. Open cir cuit po ten tial mea sure ments re vealed a dis place ment of the po ten tial in the no ble di rec tion in both me dia. How ever, reg u lar os cil la tions in the po ten tial were ob served only in the lac tate/sul fate me dium. SEM mi cro graphs showned pits clearly dis trib uted over the sur face of the steel sam ples exposed to SRB cul tures in both me dia, with small size and more uni form pits in the lac tate/sulfate me dia, in agree ment with the open cir cuit po ten tial data. Cy clic voltammetry clearly shows that the SRBs grown in the lac tate/sul fate me dium lead to high dis so lu tion rates in the transpassive re gion with the for ma tion of Fe(III) spe cies.

Attenuated total reflectance Fourier-transformed infrared (ATR-FTIR) spectroscopy measures the ch... more Attenuated total reflectance Fourier-transformed infrared (ATR-FTIR) spectroscopy measures the changes that occur in a totally internally reflected infrared beam when the evanescent wave it produces penetrates only a few micrometers (0.5-5μm) into the sample, deposited on top of an optically dense crystal (Figure 1) [1]. Both conventional FTIR and ATR-FTIR have been successfully used for bacteria discrimination and classification, as each species presents an unique spectral “fingerprint”, making it a promising, fast and reliable screening method for pathogen identification in a clinic setting [2-3]. In this study, ATR-FTIR is used in an attempt to discriminate between Escherichia (E.) coli BE BL21(DE3) and a derived mutant lacking the major E. coli porins OmpF and OmpC (Table 1). Porins are transmembrane proteins located in the outer membrane of Gram-negative bacteria such as E. coli that allow the passage of various solutes, including antibiotics, playing therefore an important rol...

Common modern techniques for bacteria identification, though rather sensitive and consistent, are... more Common modern techniques for bacteria identification, though rather sensitive and consistent, are either too specific (e.g. species-specific PCR; immunoassays), requiring preliminary analysis to avoid a trial and error approach or, on the contrary, so broad that demand subsequent testing in order to give a definitive result (e.g. broad-range PCR), leading to an excessive amount of time required for the diagnosis of infections [1, 2].

Anaerobe, 1998

A novel sulphate-reducing bacterium (Ind 1) was isolated from a biofilm removed from a severely c... more A novel sulphate-reducing bacterium (Ind 1) was isolated from a biofilm removed from a severely corroded carbon steel structure in a marine environment. Light microscopy observations revealed that cells were Gramnegative, rod shaped and very motile. Partial 16S rRNA gene sequencing and analysis of the fatty acid profile demonstrated a strong similarity between the new species and members from the Desulfovibrio genus. This was confirmed by the results obtained following purification and characterisation of the key proteins involved in the sulphate-reduction pathway. Several metal-containing proteins, such as two periplasmic proteins: hydrogenase and cytochrome c 3 , and two cytoplasmic proteins: ferredoxin and sulphite reductase, were isolated and purified. The latter proved to be of the desulfoviridin type which is typical of the Desulfovibrio genus. The study of the remaining proteins revealed a high degree of similarity with the homologous proteins isolated from Desulfovibrio gigas. However, the position of the strain within the phylogenetic tree clearly indicates that the bacterium is closely related to Desulfovibrio gabonensis, and these three strains form a separate cluster in the delta subdivision of the Proteobacteria. On the basis of the results obtained, it is suggested that Ind 1 belongs to a new species of the genus Desulfovibrio, and the name Desulfovibrio indonensis is proposed.

Journal of biophotonics, 2012

Vibrational spectroscopy has long been used in bacterial identification with different levels of ... more Vibrational spectroscopy has long been used in bacterial identification with different levels of taxonomic discrimination but its true potential for intra-species differentiation remains poorly explored. Herein, both transmission Fourier-transform infrared (FTIR) and attenuated total reflectance (ATR)-FTIR spectroscopy are used to analyse E. coli strains that differ solely in their porin expression profile. In this previously unreported approach, the applicability of both FTIR-spectroscopy techniques is compared with the same collection of unique strains. ATR-FTIR spectroscopy proved to reliably distinguish between several E. coli porin mutants with an accuracy not replicated by FTIR in transmission mode (using previously optimized procedures). Further studies should allow the identification of the individual contribution of the single porin channel to the overall bacterial infrared spectrum and of molecular predictive patterns of porin alterations.

Journal of inorganic biochemistry, 2012

Solution behavior of levofloxacin (lvx) complexes with copper(II) in the presence and absence of ... more 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)(H(2)O)](NO(3)).2H(2)O, 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 inh...

Journal of Inorganic Biochemistry, 2014

European Journal of Biochemistry, 2000

A novel molybdenum iron-sulfur-containing aldehyde oxidoreductase (AOR) belonging to the xanthine... more A novel molybdenum iron-sulfur-containing aldehyde oxidoreductase (AOR) belonging to the xanthine oxidase family was isolated and characterized from the sulfate-reducing bacterium Desulfovibrio alaskensis NCIMB 13491, a strain isolated from a soured oil reservoir in Purdu Bay, Alaska. D. alaskensis AOR is closely related to other AORs isolated from the Desulfovibrio genus. The protein is a 97-kDa homodimer, with 0.6^0.1 Mo, 3.6^0.1 Fe and 0.9^0.1 pterin cytosine dinucleotides per monomer. The enzyme catalyses the oxidation of aldehydes to their carboxylic acid form, following simple Michaelis±Menten kinetics, with the following parameters (for benzaldehyde): K app m 6.65 mm; V app 13.12 mm´min 21 ; k app cat 0.96 s 21. Three different EPR signals were recorded upon long reduction of the protein with excess dithionite: an almost axial signal split by hyperfine interaction with one proton associated with Mo(V) species and two rhombic signals with EPR parameters and relaxation behavior typical of [2Fe±2S] clusters termed Fe/S I and Fe/S II, respectively. EPR results reveal the existence of magnetic interactions between Mo(V) and one of the Fe/S clusters, as well as between the two Fe/S clusters. Redox titration monitored by EPR yielded midpoint redox potentials of 2275 and 2325 mV for the Fe/S I and Fe/S II, respectively. The redox potential gap between the two clusters is large enough to obtain differentiated populations of these paramagnetic centers. This fact, together with the observed interactions among paramagnetic centers, was used to assign the EPR-distinguishable Fe/S I and Fe/S II to those seen in the reported crystal structures of homologous enzymes.

Progress in Lipid Research, 2012

Antimicrobial peptides (AMPs) take part in the immune system by mounting a first line of defense ... more 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.

Nanomedicine: Nanotechnology, Biology and Medicine, 2014

Leishmaniasis is one of the most serious diseases in the world and can be lethal if untreated. Th... more Leishmaniasis is one of the most serious diseases in the world and can be lethal if untreated. This is especially the case for visceral leishmaniasis, which is commonly caused by Leishmania (L.) infantum and for which available medication is still inadequate. A recently described antimicrobial peptide DRS 01 has been reported to kill L. infantum promastigotes, but nothing is known about its mode of action or effect on the cell. In this paper we report the visualization of the interaction between DRS 01 and L. infantum promastigotes using two high resolution microscopic techniques: atomic force microscopy and scanning electron microscopy. The results show considerable morphological changes at and above the IC50 in the treated cells. Both membrane damage and flagella alterations were observed. The results strongly suggest a membrane-directed action for DRS 01 on the Leishmania species studied. In this paper, the effects of DRS 01, an antimicrobial peptide, is studied in Leishmania infantum using atomic force microscopy as well as standard scanning electron microscopy techniques, with the conclusion of a membrane-based effect by DRS 01 on the parasites.

Materials and Corrosion, 2000

The involvement of sulphate-reducing bacteria (SRB) in microbially influenced corrosion (MIC) of ... more The involvement of sulphate-reducing bacteria (SRB) in microbially influenced corrosion (MIC) of steel and the serious implications associated with their presence in industrial environments have long been known and extensively described. Desulfovibrio desulfuricans ATCC 27774 is an interesting metabolic case of SRB, as it can use both sulphate and nitrate as respiratory substrates during lactate oxidation. This strain has been extensively studied from both a biochemical and structural point of view but, so far, restricted information is available concerning its role in MIC. This work describes a comparative study of the corrosive aggressivity of ATCC 27774 strain towards mild steel when grown either in lactate/sulphate or lactate/nitrate media. The carbon source and electron acceptor's consumption rates were analysed and the metabolic features were correlated with weight loss measurements and SEM observations. Die Beteiligung von sulfatreduzierenden Bakterien (SRB) bei der mikrobiologisch beeinfluûten Korrosion (MIC) von Stahl und die Auswirkungen, die mit ihrer Anwesenheit in industriellen Umgebungen verbunden sind, sind seit langem bekannt und ausfu Èhrlich beschrieben. Desulfovibrio desulfuricans ATCC 27774 ist ein interessanter metabolischer Fall von SRB, da es sowohl Sulfat als auch Nitrat als Respirationssubstrat wa Èhrend der Laktatoxidation nutzen kann. Diese Art ist sowohl vom biochemischen als auch vom strukturellen Standpunkt aus intensiv untersucht worden; bisher gibt es allerdings nur begrenzte Informationen u Èber seine Rolle bei MIC. Diese Arbeit beschreibt eine Vergleichsstudie der Korrosivita Èt der ATCC 27774 Art (bei Wachstum entweder in Laktat/Sulfatoder Laktat/Nitrat-Medien) gegenu Èber unlegiertem Stahl. Die Kohlenstoffquelle und die Elektronenakzeptorverbrauchsrate wurden analysiert und die metabolischen Merkmale wurden mit Massenverlustmessungen und REM-Beobachtungen korreliert. 2 Materials and methods 2.1 Microorganisms , growth media and culture conditions Studies were performed with pure cultures of the strain Desulfovibrio desulfuricans ATCC 27774, grown in lactate/sulphate and lactate/nitrate media whose composition is described below.

Journal of Inorganic Biochemistry, 2010

Journal of Inorganic Biochemistry, 1997

Journal of Biological Inorganic Chemistry, 2004

We report the characterization of the molecular properties and EPR studies of a new formate dehyd... more We report the characterization of the molecular properties and EPR studies of a new formate dehydrogenase (FDH) from the sulfate-reducing organism Desulfovibrio alaskensis NCIMB 13491. FDHs are enzymes that catalyze the two-electron oxidation of formate to carbon dioxide in several aerobic and anaerobic organisms. D. alaskensis FDH is a heterodimeric protein with a molecular weight of 126±2 kDa composed of two subunits, a=93±3 kDa and b=32±2 kDa, which contains 6±1 Fe/molecule, 0.4±0.1 Mo/molecule, 0.3±0.1 W/molecule, and 1.3±0.1 guanine monophosphate nucleotides. The UV-vis absorption spectrum of D. alaskensis FDH is typical of an iron-sulfur protein with a broad band around 400 nm. Variable-temperature EPR studies performed on reduced samples of D. alaskensis FDH showed the presence of signals associated with the different paramagnetic centers of D. alaskensis FDH. Three rhombic signals having g-values and relaxation behavior characteristic of [4Fe-4S] clusters were observed in the 5-40 K temperature range. Two EPR signals with all the g-values less than two, which accounted for less than 0.1 spin/protein, typical of mononuclear Mo(V) and W(V), respectively, were observed. The signal associated with the W(V) ion has a larger deviation from the free electron g-value, as expected for tungsten in a d 1 configuration, albeit with an unusual relaxation behavior. The EPR parameters of the Mo(V) signal are within the range of values typically found for the slow-type signal observed in several Mo-containing proteins belonging to the xanthine oxidase family of enzymes. Mo(V) resonances are split at temperatures below 50 K by magnetic coupling with one of the Fe/S clusters. The analysis of the inter-center magnetic interaction allowed us to assign the EPR-distinguishable iron-sulfur clusters with those seen in the crystal structure of a homologous enzyme. Keywords Electron paramagnetic resonance AE Formate dehydrogenase AE Magnetic interactions AE Molybdenum-containing enzymes AE Tungsten-containing enzymes Abbreviations AOR aldehyde oxidoreductase AE FDH formate dehydrogenase AE NAP periplasmic nitrate reductase AE SRB sulfate-reducing bacteria

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2004

The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain Al1 T is Y11984. ... more The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain Al1 T is Y11984. The fatty acid profile and an AFM image of strain Al1 T , FT-IR spectra of various SRB and a dendrogram based on these spectra are available as supplementary material in IJSEM Online.

International Biodeterioration & Biodegradation, 1996

Biochemistry, 2006

The thermal unfolding of plastocyanin from the mesophilic cyanobacterium Synechocystis is describ... more 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.