Sandra Paiva | Universidade do Minho (original) (raw)

Papers by Sandra Paiva

FEMS yeast research, 2015

We have functionally characterized the four Saccharomyces cerevisiae (Sc) Jen1 homologues of Deba... more We have functionally characterized the four Saccharomyces cerevisiae (Sc) Jen1 homologues of Debaryomyces hansenii (Dh) by heterologous expression in S. cerevisiae. Debaryomyces hansenii cells display mediated transport for the uptake of lactate, acetate, succinate and malate. DHJEN genes expression was detected by RT-PCR in all carbon sources assayed, namely lactate, succinate, citrate, glycerol and glucose. The heterologous expression in the S. cerevisiae W303-1A jen1Δ ady2Δ strain demonstrated that the D. hansenii JEN genes encode four carboxylate transporters. DH27 gene encodes an acetate transporter (Km 0.94 ± 0.17 mM; Vmax 0.43 ± 0.03 nmol s(-1) mg(-1)), DH17 encodes a malate transporter (Km 0.27 ± 0.04 mM; Vmax 0.11 ± 0.01 nmol s(-1) mg(-1)) and both DH18 and DH24 encode succinate transporters with the following kinetic parameters, respectively, Km 0.31 ± 0.06 mM; Vmax 0.83 ± 0.04 nmol s(-1) mg(-1)and Km 0.16 ± 0.02 mM; Vmax 0.19 ± 0.02 nmol s(-1) mg(-1). Surprisingly, no lac...

Scientific Reports

Correlating data from different microscopy techniques holds the potential to discover new facets ... more Correlating data from different microscopy techniques holds the potential to discover new facets of signaling events in cellular biology. Here we report for the first time a hardware set-up capable of achieving simultaneous co-localized imaging of spatially correlated far-field super-resolution fluorescence microscopy and atomic force microscopy, a feat only obtained until now by fluorescence microscopy set-ups with spatial resolution restricted by the Abbe diffraction limit. We detail system integration and demonstrate system performance using sub-resolution fluorescent beads and applied to a test sample consisting of human bone osteosarcoma epithelial cells, with plasma membrane transporter 1 (MCT1) tagged with an enhanced green fluorescent protein (EGFP) at the N-terminal.

Unspecific bacterial reduction of azo dyes is a process widely studied in correlation with the bi... more Unspecific bacterial reduction of azo dyes is a process widely studied in correlation with the biological treatment of colored wastewaters, but the enzyme system associated with this bacterial capability has never been positively identified. Several ascomycete yeast strains display similar decolorizing behaviors. The yeastmediated process requires an alternative carbon and energy source and is independent of previous exposure to the dyes. When substrate dyes are polar, their reduction is extracellular, strongly suggesting the involvement of an externally directed plasma membrane redox system. The present work demonstrates that, in Saccharomyces cerevisiae, the ferric reductase system participates in the extracellular reduction of azo dyes. The S. cerevisiae ⌬fre1 and ⌬fre1 ⌬fre2 mutant strains, but not the ⌬fre2 strain, showed much-reduced decolorizing capabilities. The FRE1 gene complemented the phenotype of S. cerevisiae ⌬fre1 cells, restoring the ability to grow in medium without externally added iron and to decolorize the dye, following a pattern similar to the one observed in the wild-type strain. These results suggest that under the conditions tested, Fre1p is a major component of the azo reductase activity.

The strainSaccharomyces cerevisiaeW303-1a,ableto growin a mediumcontainingaceticacid asthe soleca... more The strainSaccharomyces cerevisiaeW303-1a,ableto growin a mediumcontainingaceticacid asthe solecarbonand energy source,wassubjectedto mutagenesis in orderto obtain mutantsdeficientin monocarboxylate permeases. Two mutant clones exhibitinggrowth in ethanol,but unableto grow in a mediumwith aceticacid as the solecarbonand energysource,were isolated(mutantsAce12andAce8).In both mutants,the activity for the acetatecarrierwasstronglyaffected.Themutant Ace8 revealednot to be affectedin the transportof lactate,whilethe mutant Ace12did not displayactivity for that carrier.These resultsreinforcedthosepreviouslyfound in the strainIGC 4072,wheretwo

Current genetics, 2007

The present work describes a detailed physiological and molecular characterization of the mechani... more The present work describes a detailed physiological and molecular characterization of the mechanisms of transport of carboxylic acids in Kluyveromyces lactis. This yeast species presents two homologue genes to JEN1 of Saccharomyces cerevisiae: KlJEN1 encodes a monocarboxylate permease and KlJEN2 encodes a dicarboxylic acid permease. In the strain K. lactis GG1888, expression of these genes does not require an inducer and activity for both transport systems was observed in glucose-grown cells. To confirm their key role for carboxylic acids transport in K. lactis, null mutants were analyzed. Heterologous expression in S. cerevisiae has been performed and chimeric fusions with GFP showed their proper localization in the plasma membrane. S. cerevisiae jen1delta cells transformed with KlJEN1 recovered the capacity to use lactic acid, as well as to transport labeled lactic acid by a mediated mechanism. When KlJEN2 was heterologously expressed, S. cerevisiae transformants gained the abilit...

Journal of bacteriology, 1999

A mutant of Saccharomyces cerevisiae deficient in the lactate-proton symport was isolated. Transf... more A mutant of Saccharomyces cerevisiae deficient in the lactate-proton symport was isolated. Transformation of the mutant with a yeast genomic library allowed the isolation of the gene JEN1 that restored lactate transport. Disruption of JEN1 abolished uptake of lactate. The results indicate that, under the experimental conditions tested, no other monocarboxylate permease is able to efficiently transport lactate in S. cerevisiae.

Unspecific bacterial reduction of azo dyes is a widely studied process in correlation with the bi... more Unspecific bacterial reduction of azo dyes is a widely studied process in correlation with the biological treatment of coloured waste waters but the enzyme system associated to this bacterial capability has never been positively identified. Several ascomycete yeast strains, ...

Endocytosis is a critical component of plasma membrane dynamics, by allowing the removal of prote... more Endocytosis is a critical component of plasma membrane dynamics, by allowing the removal of proteins such as transporters or receptors in response to environmental cues. In yeast, transporter endocytosis requires their ubiquitylation at the plasma membrane by the ...

French Spanish English. RepositoriUM. Universidade do Minho, Serviços de Documentação, Biblioteca... more French Spanish English. RepositoriUM. Universidade do Minho, Serviços de Documentação, Biblioteca Digital, Catálogo Bibliográfico, . Homepage. Login. Contactos. FAQ. E-Mail. Print. Pesquisa rápida. Pesquisa avançada. Percorrer: Comunidades & Colecções. Título. Autor. ...

Carboxylic acids are widely used in pharmaceutical and food industries and new industrial uses ar... more Carboxylic acids are widely used in pharmaceutical and food industries and new industrial uses are continually emerging. The first step of carboxylic acids metabolism is their entrance to the cell and understanding in detail this process has significant biotechnological ...

The emergence of probiotics and prebiotics has revived the importance of short-chain fatty acids ... more The emergence of probiotics and prebiotics has revived the importance of short-chain fatty acids (SCFAs) associated to colonic and systemic health improvement. Although biosynthesis and degradation of SCFAs and other short-chain carboxylic acids, such as ...

The intracellular trafficking of plasma membrane proteins, such as receptors and transporters, in... more The intracellular trafficking of plasma membrane proteins, such as receptors and transporters, in eukaryotic cells is a highly regulatedprocess. Changing environment conditions (nutrients, substrates, hormones) can trigger endocytosis of unwanted ...

The S. cerevisiae membrane protein Jen1 is a monocarboxylate-proton symporter which after the add... more The S. cerevisiae membrane protein Jen1 is a monocarboxylate-proton symporter which after the addition of glucose to lactic acid-grown cells triggers loss of Jen1p activity and repression of JEN1 gene expression (Paiva et al., 2002; Andrade et al., 2001). This ...

DC reactive magnetron sputtered Ag:TiO 2 nanocomposite thin films were developed to be used as pr... more DC reactive magnetron sputtered Ag:TiO 2 nanocomposite thin films were developed to be used as protective coatings in pressure sensor devices. The coatings, with Ag content varying from 0 to about 30 at.%, were prepared and characterized in order to study their biological response. The as-deposited samples were annealed in vacuum at 500°C in order to evaluate the influence of their morphological and structural differences over the response elicited upon contact with simulated bodily fluids and cultured human cells, as well as selected microorganisms. The results showed that the annealing treatment produced less porous films with an enhanced structure, with a significant reduction in structural defects and improved crystallinity. Additionally, samples with higher Ag contents (C12.8 at.%) exhibited Ag agglomerates/clusters at the surface, a result anticipated from the XRD data. The crystallization of the TiO 2 matrix was also observed by XRD analysis, albeit delayed by the dispersion of Ag into the matrix. Biological characterization showed that the antimicrobial activity and cytotoxicity of the coatings were directly related with their composition, closely followed by the particular structural and morphological features, namely those resulting from annealing process.

FEMS yeast research, 2015

We have functionally characterized the four Saccharomyces cerevisiae (Sc) Jen1 homologues of Deba... more We have functionally characterized the four Saccharomyces cerevisiae (Sc) Jen1 homologues of Debaryomyces hansenii (Dh) by heterologous expression in S. cerevisiae. Debaryomyces hansenii cells display mediated transport for the uptake of lactate, acetate, succinate and malate. DHJEN genes expression was detected by RT-PCR in all carbon sources assayed, namely lactate, succinate, citrate, glycerol and glucose. The heterologous expression in the S. cerevisiae W303-1A jen1Δ ady2Δ strain demonstrated that the D. hansenii JEN genes encode four carboxylate transporters. DH27 gene encodes an acetate transporter (Km 0.94 ± 0.17 mM; Vmax 0.43 ± 0.03 nmol s(-1) mg(-1)), DH17 encodes a malate transporter (Km 0.27 ± 0.04 mM; Vmax 0.11 ± 0.01 nmol s(-1) mg(-1)) and both DH18 and DH24 encode succinate transporters with the following kinetic parameters, respectively, Km 0.31 ± 0.06 mM; Vmax 0.83 ± 0.04 nmol s(-1) mg(-1)and Km 0.16 ± 0.02 mM; Vmax 0.19 ± 0.02 nmol s(-1) mg(-1). Surprisingly, no lac...

Scientific Reports

Correlating data from different microscopy techniques holds the potential to discover new facets ... more Correlating data from different microscopy techniques holds the potential to discover new facets of signaling events in cellular biology. Here we report for the first time a hardware set-up capable of achieving simultaneous co-localized imaging of spatially correlated far-field super-resolution fluorescence microscopy and atomic force microscopy, a feat only obtained until now by fluorescence microscopy set-ups with spatial resolution restricted by the Abbe diffraction limit. We detail system integration and demonstrate system performance using sub-resolution fluorescent beads and applied to a test sample consisting of human bone osteosarcoma epithelial cells, with plasma membrane transporter 1 (MCT1) tagged with an enhanced green fluorescent protein (EGFP) at the N-terminal.

Unspecific bacterial reduction of azo dyes is a process widely studied in correlation with the bi... more Unspecific bacterial reduction of azo dyes is a process widely studied in correlation with the biological treatment of colored wastewaters, but the enzyme system associated with this bacterial capability has never been positively identified. Several ascomycete yeast strains display similar decolorizing behaviors. The yeastmediated process requires an alternative carbon and energy source and is independent of previous exposure to the dyes. When substrate dyes are polar, their reduction is extracellular, strongly suggesting the involvement of an externally directed plasma membrane redox system. The present work demonstrates that, in Saccharomyces cerevisiae, the ferric reductase system participates in the extracellular reduction of azo dyes. The S. cerevisiae ⌬fre1 and ⌬fre1 ⌬fre2 mutant strains, but not the ⌬fre2 strain, showed much-reduced decolorizing capabilities. The FRE1 gene complemented the phenotype of S. cerevisiae ⌬fre1 cells, restoring the ability to grow in medium without externally added iron and to decolorize the dye, following a pattern similar to the one observed in the wild-type strain. These results suggest that under the conditions tested, Fre1p is a major component of the azo reductase activity.

The strainSaccharomyces cerevisiaeW303-1a,ableto growin a mediumcontainingaceticacid asthe soleca... more The strainSaccharomyces cerevisiaeW303-1a,ableto growin a mediumcontainingaceticacid asthe solecarbonand energy source,wassubjectedto mutagenesis in orderto obtain mutantsdeficientin monocarboxylate permeases. Two mutant clones exhibitinggrowth in ethanol,but unableto grow in a mediumwith aceticacid as the solecarbonand energysource,were isolated(mutantsAce12andAce8).In both mutants,the activity for the acetatecarrierwasstronglyaffected.Themutant Ace8 revealednot to be affectedin the transportof lactate,whilethe mutant Ace12did not displayactivity for that carrier.These resultsreinforcedthosepreviouslyfound in the strainIGC 4072,wheretwo

Current genetics, 2007

The present work describes a detailed physiological and molecular characterization of the mechani... more The present work describes a detailed physiological and molecular characterization of the mechanisms of transport of carboxylic acids in Kluyveromyces lactis. This yeast species presents two homologue genes to JEN1 of Saccharomyces cerevisiae: KlJEN1 encodes a monocarboxylate permease and KlJEN2 encodes a dicarboxylic acid permease. In the strain K. lactis GG1888, expression of these genes does not require an inducer and activity for both transport systems was observed in glucose-grown cells. To confirm their key role for carboxylic acids transport in K. lactis, null mutants were analyzed. Heterologous expression in S. cerevisiae has been performed and chimeric fusions with GFP showed their proper localization in the plasma membrane. S. cerevisiae jen1delta cells transformed with KlJEN1 recovered the capacity to use lactic acid, as well as to transport labeled lactic acid by a mediated mechanism. When KlJEN2 was heterologously expressed, S. cerevisiae transformants gained the abilit...

Journal of bacteriology, 1999

A mutant of Saccharomyces cerevisiae deficient in the lactate-proton symport was isolated. Transf... more A mutant of Saccharomyces cerevisiae deficient in the lactate-proton symport was isolated. Transformation of the mutant with a yeast genomic library allowed the isolation of the gene JEN1 that restored lactate transport. Disruption of JEN1 abolished uptake of lactate. The results indicate that, under the experimental conditions tested, no other monocarboxylate permease is able to efficiently transport lactate in S. cerevisiae.

Unspecific bacterial reduction of azo dyes is a widely studied process in correlation with the bi... more Unspecific bacterial reduction of azo dyes is a widely studied process in correlation with the biological treatment of coloured waste waters but the enzyme system associated to this bacterial capability has never been positively identified. Several ascomycete yeast strains, ...

Endocytosis is a critical component of plasma membrane dynamics, by allowing the removal of prote... more Endocytosis is a critical component of plasma membrane dynamics, by allowing the removal of proteins such as transporters or receptors in response to environmental cues. In yeast, transporter endocytosis requires their ubiquitylation at the plasma membrane by the ...

French Spanish English. RepositoriUM. Universidade do Minho, Serviços de Documentação, Biblioteca... more French Spanish English. RepositoriUM. Universidade do Minho, Serviços de Documentação, Biblioteca Digital, Catálogo Bibliográfico, . Homepage. Login. Contactos. FAQ. E-Mail. Print. Pesquisa rápida. Pesquisa avançada. Percorrer: Comunidades & Colecções. Título. Autor. ...

Carboxylic acids are widely used in pharmaceutical and food industries and new industrial uses ar... more Carboxylic acids are widely used in pharmaceutical and food industries and new industrial uses are continually emerging. The first step of carboxylic acids metabolism is their entrance to the cell and understanding in detail this process has significant biotechnological ...

The emergence of probiotics and prebiotics has revived the importance of short-chain fatty acids ... more The emergence of probiotics and prebiotics has revived the importance of short-chain fatty acids (SCFAs) associated to colonic and systemic health improvement. Although biosynthesis and degradation of SCFAs and other short-chain carboxylic acids, such as ...

The intracellular trafficking of plasma membrane proteins, such as receptors and transporters, in... more The intracellular trafficking of plasma membrane proteins, such as receptors and transporters, in eukaryotic cells is a highly regulatedprocess. Changing environment conditions (nutrients, substrates, hormones) can trigger endocytosis of unwanted ...

The S. cerevisiae membrane protein Jen1 is a monocarboxylate-proton symporter which after the add... more The S. cerevisiae membrane protein Jen1 is a monocarboxylate-proton symporter which after the addition of glucose to lactic acid-grown cells triggers loss of Jen1p activity and repression of JEN1 gene expression (Paiva et al., 2002; Andrade et al., 2001). This ...

DC reactive magnetron sputtered Ag:TiO 2 nanocomposite thin films were developed to be used as pr... more DC reactive magnetron sputtered Ag:TiO 2 nanocomposite thin films were developed to be used as protective coatings in pressure sensor devices. The coatings, with Ag content varying from 0 to about 30 at.%, were prepared and characterized in order to study their biological response. The as-deposited samples were annealed in vacuum at 500°C in order to evaluate the influence of their morphological and structural differences over the response elicited upon contact with simulated bodily fluids and cultured human cells, as well as selected microorganisms. The results showed that the annealing treatment produced less porous films with an enhanced structure, with a significant reduction in structural defects and improved crystallinity. Additionally, samples with higher Ag contents (C12.8 at.%) exhibited Ag agglomerates/clusters at the surface, a result anticipated from the XRD data. The crystallization of the TiO 2 matrix was also observed by XRD analysis, albeit delayed by the dispersion of Ag into the matrix. Biological characterization showed that the antimicrobial activity and cytotoxicity of the coatings were directly related with their composition, closely followed by the particular structural and morphological features, namely those resulting from annealing process.