50 research outputs found
Microbial Populations in Ferrous Iron Oxidation Bioreactors
Motivación: ferrous iron oxidation can take place in partly controlled biological reactors inoculated with mixed cultures of acidophilic microorganisms. In these bioreactors, liquor pH can affect productivity. We aimed at determining whether productivity changes are directly due to the chemistry of iron precipitation or due to microbial population changes.Methods: flooded (with 9K standard medium) packed-bed (randomly packed with siliceous stone particles between 6 and 8 mm in size; 0.42 porosity) bioreactors (cylinders 4.32 cm in diameter and 10 cm in height) were operated in continuous mode, with controlled temperature (310C), fed at constant liquid flow rate (100 mL/h), and constantly aerated with two different air-flow rates (250 and 500 mL/min). Liquor inlet pH in bioreactors was change in the range 1.9-0.8. Outlet pH was measured with a standard pH-meter and ferric iron productivities (g/h) were measured in an automatic titrator using the standard potassium dichromate method. Microbial identification was done by phylogenetic analyses of 16S rRNA sequences obtained after PCR, cloning, transformation, and sequencing.Results and conclusions: Operation pH does not affect bioreactor productivity in the range from 1 to 2.3. Falls in productivity are essentially due to ferric iron precipitation chemistry. If upper pH limit is exceed, productivity can be recovered lowering pH; conversely, if lower pH limit is exceed, productivity never recovers though pH is increased. The microbial population of the bioreactor changes with changes in pH, being 1.3 the pH transition value. Above pH 1.3 acidithiobacilli are the dominant microorganisms, while below pH 1.3 leptospirilli are the dominant ones. Thus, we conclude that the microbial population inside the bioreactor behave in a highly versatile manner, allowing productivity to remains virtually unchanging. The versatility turns this kind of bioreactor into a highly flexible platform for ferrous iron oxidation; stepwise pH changes can result into perfectly adapted microbial populations, the basis to treat industrial influent liquor at different pHs. This kind of bioreactor and operation mode has been successfully applied at semi-industrial scale
Inhibition of the adenylylation of liver plasma membrane-bound proteins by plant and mammalian lectins
Liver plasma membrane contains four major (130-kDa, 120-kDa, 110-kDa and 100-kDa) sialic acid-containing glycopolypeptides that are able to undergo adenylylation, as well as phosphorylation (San José et al. (1990) J. Biol. Chem. 265; 20653-20661). To gain insight into the regulation of these processes, lectins are employed to probe the extent of influence of their interaction with membrane fractions for these reactions. We demonstrate that the beta-galactoside-specific lectins from bovine heart and mistletoe at low concentrations inhibit the adenylylation of this set of plasma membrane glycopolypeptides. The extent of phosphorylation of these polypeptides is also reduced although to a lesser degree. Concanavalin A, too, inhibits the adenylylation of the plasma membrane glycopolypeptides, although higher concentrations of this lectin were required, whereas wheat germ lectin has only a very small inhibitory effect. The adenylylable polypeptides were isolated by concanavalin A-agarose chromatography upon elution with mannose. In agreement with this result, control experiments with a panel of neoglycoproteins indicate that mannose residues appear to be required for the concanavalin A-induced inhibition of the adenylylation. Neoglycoproteins containing mannose 6-phosphate, lactose, fucose, or sialic acid instead of mannose lack the ability to protect the adenylylation from the inhibitory action of concanavalin A. In contrast, none of the above-mentioned neoglycoproteins, nor asialofetuin, nor galactose-containing saccharides protect the adenylylation against the inhibitory effect of both the mistletoe and bovine heart lectins, emphasizing the importance of either high affinity carbohydrate ligands in the overall process, or other ligand sites for the lectins beside carbohydrates to affect the regulation of the adenylylation system.This work was supported in part by grants (to A.V.) from the Dirección General de Investigación Científica y Técnica (PB 89-0079). and from the Consejería de Educación de la Comunidad de Madrid (C174-90 and 366/92) Spain, grants (to H.-J.G.) from the Dr. M. Scheel-Stiftung für Krebsforschung and the BMFT program Alternative Methoden der Krebsbekämpfung, Germany, and the Acciones Imegradas (42A) between Germany and Spain (to H.-J.G. andA.V.). E.S.J. is the recipient of a predoctoral fellowship from the Departamento de Educación, Universidades e Investigación del Gobierno Vasco.Peer Reviewe
Pasteur, el padre de la Microbiología moderna
En diciembre de este año 2022 se celebra el bicentenario del nacimiento de Louis
Pasteur, uno de los científicos franceses
más sobresalientes, que estuvo a la altura
de científicas de ese país galardonadas con
el Premio Nobel como Maria Skłodowska, su hija Irène Joliot-Curie o Françoise
Barré-Sinoussi. Pasteur es un personaje de la cultura francesa tan reconocible
como las escritoras Simone de Beauvoir o
Madame de La Fayette. El ilustre Pasteur
fue y es tan importante para su país que
da su nombre a una de las dos únicas instituciones científicas que en Francia llevan
nombres propios, el Institut Pasteur; la otra
es el Institut Curie.. Pasteur es además un icono del país vecino tan universal y conocido por todos como la révolution française de 1789, la Tour Eiffel o la baguette. ¿Quién no ha oído hablar alguna vez de la pasteurización?, ese proceso térmico que lleva su nombre, que evita enfermedades transmitidas por alimentos y ha salvado tantas vidas. Aquí contaré algunos aspectos de la vida de Pasteur y reseñaré sus principales logros científicos de forma resumida y no siempre cronológica. La ilustración de Pasteur mostrada al principio de este artículo, realizada por @CireniaSketches, forma parte de las acciones que desde la Universidad de Sevilla llevo a cabo para conmemorar los 200 años del nacimiento de Louis Pasteur
Microbial Populations in Ferrous Iron Oxidation Bioreactors
Motivación: ferrous iron oxidation can take place in partly controlled biological reactors inoculated with mixed cultures of acidophilic microorganisms. In these bioreactors, liquor pH can affect productivity. We aimed at determining whether productivity changes are directly due to the chemistry of iron precipitation or due to microbial population changes
Operational pH in packed-bed reactors for ferrous ion bio-oxidation
The flooded packed-bed bioreactor plays a major role in the field of applications of ferrous ion bio-oxidation. The
pH is an important variable in the control of this type of reactor, upon which the functionality of biofilm depends.
In the present work, five continuous flooded packed-bed reactors have been inoculated with mixed cultures
(Acidithiobacillus ferrooxidans and Leptospirillum ferooxidans) and fed with 9 k medium in the pH range 0.82 to 1.90.
It has been experimentally tested that the operation of these reactors is stable at the maximum productivity levels
when the pH varies within the interval 1.00 to 2.30 inside the reactor.
It has been observed that the negative effect on the productivity when the upper pH limit is exceeded is reversible.
No such reversibility occurs when the pH goes below the lower limit.
The results of our experiments indicate that the limitations in operational pH are linked to the chemistry of
precipitation ferric compounds and not to biological phenomena
The role of the calmodulin-binding and calmodulin-like domains of the epidermal growth factor receptor in tyrosine kinase activation
The epidermal growth factor receptor (EGFR) harbors a calmodulin (CaM)-binding domain (CaM-BD) and a CaM-like domain (CaM-LD) upstream and downstream, respectively, of the tyrosine kinase (TK) domain. We demonstrate in this paper that deletion of the positively charged CaM-BD (EGFR/CaM-BD∆) inactivated the TK activity of the receptor. Moreover, deletion of the negatively charged CaM-LD (EGFR/CaM-LD∆), leaving a single negative residue (glutamate), reduced the activity of the receptor. In contrast, substituting the CaM-LD with a histidine/valine-rich peptide (EGFR/InvCaM-LD) caused full inactivation. We also demonstrated using confocal microscopy and flow cytometry that the chimera EGFR-green fluorescent protein (GFP)/CaM-BD∆, the EGFR/CaM-LD∆, and EGFR/InvCaM-LD mutants all bind tetramethylrhodamine-labelled EGF. These EGFR mutants were localized at the plasma membrane as the wild-type receptor does. However, only the EGFR/CaM-LD∆ and EGFR/InvCaM-LD mutants appear to undergo ligand-dependent internalization, while the EGFR-GFP/CaM-BD∆ mutant seems to be deficient in this regard. The obtained results and in silico modelling studies of the asymmetric structure of the EGFR kinase dimer support a role of a CaM-BD/CaM-LD electrostatic interaction in the allosteric activation of the EGFR TK.Consejería de Educación, Juventud y Deportes–Comunidad de Madrid,Grant/Award Number: B2017/BMD‐36involving contributions from the EuropeanFunds for Regional Development (EFRD) andthe Social European Fund (SEF); ConsejoSuperior de Investigaciones Científicas, Grant/Award Number: COOPA20053;Secretaría de Estado de Investigación, Desarrollo e Innovación, Grant/Award Number: SAF2014‐52048‐R; Agencia Española de Cooperación Internacional para el Desarrollo, Grant/Award Numbers: A/019018/08,A/5444/06, A/8197/0
SYMBIOSIS IN THE COLD: IDENTIFICATION AND CHARACTERIZATION OF A NEW FRANCISELLA ENDOSYMBIONT FROM THE POLAR CILIATE, EUPLOTES PETZI
Ciliates of the genus Euplotes are commonly found in polar environments, and different species isolated from Arctic and Antarctic coastal seawaters are currently studied for their genome evolution and adaptation. In analyzing whole genome sequences of a wild-type E. petzi strain collected from Terra Nova Bay (Antarctica), it appeared that more than 3% of the assembled contigs had a bacterial origin and overlapped (one contig containing rDNA operon included) with DNA sequences of the gammaproteobacterium Francisella (represented by extremely infectious species to a wide array of different organisms man included).
Given that an Euplotes species of temperate seawaters, E. raikovi, has already been found to host a Francisella species (namely F. endociliophora), we searched for and succeeded in isolating Francisella-like endosymbionts from E. petzi cells. Colonies of these endosymbionts (grown optimally at
a temperature range from 4 to maximum 30 °C) have been analyzed for their genome and found to represent a new clade with a basal position in
the Francisella phylogenetic tree. This clade is unequivocally distinct from F. endociliophora (living in E. raikovi) as well as from all the other well recognised Francisella clades.
The finding that Francisella is adapted to live in the extreme environmental conditions of the polar regions implies that this bacterium is much more
common and geographically widespread than previously known, and that free-living Euplotes species may represent a natural reservoir of Francisella in every aquatic environments
The Terminal Extensions of Dbp7 Influence Growth and 60S Ribosomal Subunit Biogenesis in Saccharomyces cerevisiae
Ribosome synthesis is a complex process that involves a large set of protein trans-acting factors, among them DEx(D/H)-box helicases. These are enzymes that carry out remodelling activities onto RNAs by hydrolysing ATP. The nucleolar DEGD-box protein Dbp7 is required for the biogenesis of large 60S ribosomal subunits. Recently, we have shown that Dbp7 is an RNA helicase that regulates the dynamic base-pairing between the snR190 small nucleolar RNA and the precursors of the ribosomal RNA within early pre-60S ribosomal particles. As the rest of DEx(D/H)-box proteins, Dbp7 has a modular organization formed by a helicase core region, which contains conserved motifs, and variable, non-conserved N- and C-terminal extensions. The role of these extensions remains unknown. Herein, we show that the N-terminal domain of Dbp7 is necessary for efficient nuclear import of the protein. Indeed, a basic bipartite nuclear localization signal (NLS) could be identified in its N-terminal domain. Removal of this putative NLS impairs, but does not abolish, Dbp7 nuclear import. Both N- and C-terminal domains are required for normal growth and 60S ribosomal subunit synthesis. Furthermore, we have studied the role of these domains in the association of Dbp7 with pre-ribosomal particles. Altogether, our results show that the N- and C-terminal domains of Dbp7 are important for the optimal function of this protein during ribosome biogenesis.Ministerio de Ciencia e Innovación PID2019-103850-GB-I00Junta de Andalucía P20_00581, BIO-271, BIO-210Universidad de Sevilla US-138039
Reevaluation of the phylogenetic relationship between Mobilid and Sessilid peritrichs (Ciliophora, Oligohymenophorea) based on small subunit rRNA genes sequences
Based on morphological characters, peritrich ciliates (Class Olygohymenophorea, Subclass Peritrichia) have been subdivided into the Orders Sessilida and Mobilida. Molecular phylogenetic studies on peritrichs have been restricted to members of the Order Sessilida. In order to shed more light into the evolutionary relationships within peritrichs, the complete small subunit rRNA (SSU rRNA) sequences of four mobilid species, Trichodina nobilis, Trichodina heterodentata, Trichodina reticulata, and Trichodinella myakkae were used to construct phylogenetic trees using maximum parsimony, neighbor joining, and Bayesian analyses. Whatever phylogenetic method used, the peritrichs did not constitute a monophyletic group: mobilid and sessilid species did not cluster together. Similarity in morphology but difference in molecular data led us to suggest that the oral structures of peritrichs are the result of evolutionary convergence. In addition, Trichodina reticulata, a Trichodina species with granules in the center of the adhesive disc, branched separately from its congeners, Trichodina nobilis and Trichodina heterodentata, trichodinids without such granules. This indicates that granules in the adhesive disc might be a phylogenetic character of high importance within the Family Trichodinidae.Based on morphological characters, peritrich ciliates (Class Olygohymenophorea, Subclass Peritrichia) have been subdivided into the Orders Sessilida and Mobilida. Molecular phylogenetic studies on peritrichs have been restricted to members of the Order Sessilida. In order to shed more light into the evolutionary relationships within peritrichs, the complete small subunit rRNA (SSU rRNA) sequences of four mobilid species, Trichodina nobilis, Trichodina heterodentata, Trichodina reticulata, and Trichodinella myakkae were used to construct phylogenetic trees using maximum parsimony, neighbor joining, and Bayesian analyses. Whatever phylogenetic method used, the peritrichs did not constitute a monophyletic group: mobilid and sessilid species did not cluster together. Similarity in morphology but difference in molecular data led us to suggest that the oral structures of peritrichs are the result of evolutionary convergence. In addition, Trichodina reticulata, a Trichodina species with granules in the center of the adhesive disc, branched separately from its congeners, Trichodina nobilis and Trichodina heterodentata, trichodinids without such granules. This indicates that granules in the adhesive disc might be a phylogenetic character of high importance within the Family Trichodinidae
Alpha-Tubulin and Small Subunit rRNA Phylogenies of Peritrichs Are Congruent and Do Not Support the Clustering of Mobilids and Sessilids (Ciliophora, Oligohymenophorea)
Peritrich ciliates have been traditionally subdivided into two orders, Sessilida and Mobilida within the subclass Peritrichia. However, all the existing small subunit (SSU) rRNA phylogenetic trees showed that the sessilids and mobilids did not branch together. To shed some light on this disagreement, we tested whether or not the classic Peritrichia is a monophyletic group by assessing the reliability of the SSU rRNA phylogeny in terms of congruency with alpha-tubulin phylogeny. For this purpose, we obtained 10 partial alpha-tubulin sequences from peritrichs and built phylogenetic trees based on alpha-tubulin nucleotide and amino acid data. A phylogenetic tree from the alpha-tubulin and SSU rRNA genes in combination was also constructed and compared with that from the SSU rRNA gene using a similar species sampling. Our results show that the mobilids and sessilids are consistently separated in all trees, which reinforces the idea that the peritrichs do not constitute a monophyletic group. However, in all alpha-tubulin gene trees, the urceolariids and trichodiniids do not group together, suggested mobilids may not be a monophyletic group