Papers by Christian Magni
World Journal of Microbiology & Biotechnology, Jul 13, 2023
Applied and Environmental Microbiology, May 1, 2013
Enterococcus faecalis encodes a biotin-dependent oxaloacetate decarboxylase (OAD), which is const... more Enterococcus faecalis encodes a biotin-dependent oxaloacetate decarboxylase (OAD), which is constituted by four subunits: E. faecalis carboxyltransferase subunit OadA (termed Ef-A), membrane pump Ef-B, biotin acceptor protein Ef-D, and the novel subunit Ef-H. Our results show that in E. faecalis, subunits Ef-A, Ef-D, and Ef-H form a cytoplasmic soluble complex (termed Ef-AHD) which is also associated with the membrane. In order to characterize the role of the novel Ef-H subunit, coexpression of oad genes was performed in Escherichia coli, showing that this subunit is vital for Ef-A and Ef-D interaction. Diminished growth of the oadA and oadD single deletion mutants in citrate-supplemented medium indicated that the activity of the complex is essential for citrate utilization. Remarkably, the oadB-deficient strain was still capable of growing to wild-type levels but with a delay during the citrate-consuming phase, suggesting that the soluble Ef-AHD complex is functional in E. faecalis. These results suggest that the Ef-AHD complex is active in its soluble form, and that it is capable of interacting in a dynamic way with the membrane-bound Ef-B subunit to achieve its maximal alkalinization capacity during citrate fermentation.
Applied and Environmental Microbiology, Aug 1, 2013
The putative citrate metabolic pathway in Lactobacillus casei ATCC 334 consists of the transporte... more The putative citrate metabolic pathway in Lactobacillus casei ATCC 334 consists of the transporter CitH, a proton symporter of the citrate-divalent metal ion family of transporters CitMHS, citrate lyase, and the membrane-bound oxaloacetate decarboxylase complex OAD-ABDH. Resting cells of Lactobacillus casei ATCC 334 metabolized citrate in complex with Ca 2؉ and not as free citrate or the Mg 2؉-citrate complex, thereby identifying Ca 2؉-citrate as the substrate of the transporter CitH. The pathway was induced in the presence of Ca 2؉ and citrate during growth and repressed by the presence of glucose and of galactose, most likely by a carbon catabolite repression mechanism. The end products of Ca 2؉-citrate metabolism by resting cells of Lb. casei were pyruvate, acetate, and acetoin, demonstrating the activity of the membrane-bound oxaloacetate decarboxylase complex OAD-ABDH. Following pyruvate, the pathway splits into two branches. One branch is the classical citrate fermentation pathway producing acetoin by ␣-acetolactate synthase and ␣-acetolactate decarboxylase. The other branch yields acetate, for which the route is still obscure. Ca 2؉-citrate metabolism in a modified MRS medium lacking a carbohydrate did not significantly affect the growth characteristics, and generation of metabolic energy in the form of proton motive force (PMF) was not observed in resting cells. In contrast, carbohydrate/Ca 2؉-citrate cometabolism resulted in a higher biomass yield in batch culture. However, also with these cells, no generation of PMF was associated with Ca 2؉-citrate metabolism. It is concluded that citrate metabolism in Lb. casei is beneficial when it counteracts acidification by carbohydrate metabolism in later growth stages.
El interés por la genética en bacterias lácticas (BAL) surge en los años 70 a partir del interés ... more El interés por la genética en bacterias lácticas (BAL) surge en los años 70 a partir del interés industrial por este heterogéneo grupo de bacterias. El rápido desarrollo concomitante de la genética en BAL fue fruto del aporte de numerosos jóvenes investigadores en diversas partes del mundo inspirados por los trabajos de genética realizados tanto en Escherichia coli como Bacillus subtilis. Así, durante la primera década de la exploración de la genética en dichas bacterias, se identificaron los genes requeridos para el transporte y metabolismo de azúcares, sistemas proteolíticos, producción de bacteriocinas, caracterización y mecanismos de resistencia a fagos. Los estudios iniciales se focalizaron en estas propiedades que resultaban inestables cuando las bacterias lácticas eran sometidos al estrés asociado a los procesos industriales. La caracterización molecular de la pérdida de estos fenotipos permitió aislar numerosos plásmidos, además se encontraron asociadas a transposones y que elementos genéticos móviles determinaban la inestabilidad génica de las mismas. Un importante avance en la manipulación genética en BAL se produce con la posibilidad de introducir moléculas recombinantes a través de la técnica de electroporación, con ello se inició la construcción de numerosas herramientas que permitieron la expresión de proteínas y la posibilidad de manipular las vías metabólicas presentes en BAL. Si bien E. coli sigue siendo actualmente el hospedador de elección para la producción industrial de proteínas farmacéuticas ya que resulta genéticamente accesible y además resulta muy costoso en términos económicos el cambio de estrategia de producción una vez que un organismo ha sido establecido como hospedador en un desarrollo biotecnológico. En la búsqueda de un huésped alternativo para la producción de proteínas recombinantes, las BAL se presentan como una opción atractiva ofreciendo varias ventajas. Las mismas poseen un estatus de seguras para el consumo humano (GRAS) por lo que pueden ser utilizadas para la producción de proteínas de uso en humanos. A partir de la publicación de la secuencia completa del genoma de Lactococcus lactis en el año 2001 se avanzó en la posibilidad de modificar esta bacteria destinada a la producción de proteínas recombinantes y en la redirección de sus vías metabólicas. De esta manera en las últimas décadas se logró la producción de metabolitos de alto valor, enzimas hidrolíticas, péptidos terapéuticos, interleuquinas y diversas vitaminas (tablas 1, 2 y 3) (2, 6, 7, 9, 20-23, 30, 31, 34, 35). En los próximos párrafos describiremos las herramientas frecuentemente utilizadas para la manipulación genética de BAL. Debido a la importancia de este grupo de bacterias en la producción de alimentos. Se espera que el dominio de esta tecnología permita en el futuro desarrollar alimentos con nuevas propiedades nutricionales y farmacológicas accesibles para toda la población.Fil: Blancato, Victor Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Marelli, Belkis Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Espariz, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Suárez, Cristian Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Repizo, Guillermo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Magni, Christian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentin
Acta Tropica, May 1, 2023
International Dairy Journal, 2016
International Journal of Food Microbiology, 2016
Fems Microbiology Letters, Mar 1, 1996
Plasmid pCIT264 from Luctococcus lactis subsp. lactis biovar diacetylactis (L. diacetylactis) con... more Plasmid pCIT264 from Luctococcus lactis subsp. lactis biovar diacetylactis (L. diacetylactis) contains an insertion sequence (IS&like element located in the citrate utilization (citQRP) cluster. This 967-nucleotide long element is bounded by 17 bp perfect inverted repeats and contains an open reading frame (ORFl) composed of 296 codons, which could encode a transposase. Expression of the IS from pCIT264 generates two mRNAs of 2900 and 1900 nucleotides. The transcription is driven by the P3 promoter, composed of a-10 region located at the right end of the IS and of a-35 region positioned downstream of this element. The IS-like element (IS982) is present in seven copies in the L. diacetylactis genome. The copy present in pCIT264 is highly stable and does not promote rearrangements of the tit cluster. We suggest that the stable maintenance of the IS-like element in pCIT264 could be due to a translational control of the putative transposase by an antisense RNA.
Food Research International
Journal of Bacteriology, Jan 15, 2012
Frontiers in Microbiology
Enterococcus is able to grow in media at pH from 5.0 to 9.0 and a high concentration of NaCl (8%)... more Enterococcus is able to grow in media at pH from 5.0 to 9.0 and a high concentration of NaCl (8%). The ability to respond to these extreme conditions requires the rapid movement of three critical ions: proton (H+), sodium (Na+), and potassium (K+). The activity of the proton F0F1 ATPase and the sodium Na+ V0V1 type ATPase under acidic or alkaline conditions, respectively, is well established in these microorganisms. The potassium uptake transporters KtrI and KtrII were described in Enterococcus hirae, which were associated with growth in acidic and alkaline conditions, respectively. In Enterococcus faecalis, the presence of the Kdp (potassium ATPase) system was early established. However, the homeostasis of potassium in this microorganism is not completely explored. In this study, we demonstrate that Kup and KimA are high-affinity potassium transporters, and the inactivation of these genes in E. faecalis JH2-2 (a Kdp laboratory natural deficient strain) had no effect on the growth p...
Molecular Aspects of …, 2008
This article cites 57 articles, 34 of which can be accessed free
Genome announcements, Jan 8, 2013
Lactococcus lactis subsp. lactis strain YF11 is a food preservative bacterium with a high capacit... more Lactococcus lactis subsp. lactis strain YF11 is a food preservative bacterium with a high capacity to produce nisin. Here, we announce the draft genome sequence of Lactococcus lactis subsp. lactis YF11 (2,527,433 bp with a G+C content of 34.81%).
Antonie van Leeuwenhoek, 2020
We study the effects of the Kaluza-Klein gravitons in the Randall-Sundrum model on the recent BNL... more We study the effects of the Kaluza-Klein gravitons in the Randall-Sundrum model on the recent BNL measurements of the muon (g -2) deviation from the standard model prediction. By examining the J-partial wave unitarity bounds of the elastic process γγ → γγ, the cut-off on the number of massive KK gravitons, n c , has been introduced. We found that the recently measured ∆a µ can be accommodated in the RS model, within the natural parameter space allowed by the perturbative unitarity. For example, dozens (hundreds) of the n c for Λ π = 1 ∼ 2 TeV (3 TeV) can explain the reported ∆a µ .
Molecular Microbiology, 2019
Enterococci are gram‐positive pathogens and lead to cause hospital‐acquired infections worldwide.... more Enterococci are gram‐positive pathogens and lead to cause hospital‐acquired infections worldwide. Central carbon metabolism was shown as highly induced in Enterococcus faecalis during infection context. Metabolism of α‐polysaccharides was previously described as an important factor for host colonisation and biofilm formation. A better characterisation of the adaptation of this bacterium to carbohydrate availabilities may lead to a better understanding of the link between carbohydrate metabolism and the infection process of E. faecalis. Here we show that MalR, a LacI/GalR transcriptional regulator, is the main factor in the regulation of the two divergent operons involved in maltose metabolism in this bacterium. The malR gene is transcribed from the malP promoter, but also from an internal promoter inside the gene located upstream of malR. In the absence of maltose, MalR acts as a repressor and in the presence of glucose, it exerts efficient CcpA‐independent carbon catabolite repression. The central PTS protein P‐Ser‐HPr interacts directly with MalR and enhances its DNA binding capacity, which allows E. faecalis to adapt its metabolism to environmental conditions.
International journal of food microbiology, Jan 20, 2018
The members of the Enterococcus genus are widely distributed in nature. Its strains have been ext... more The members of the Enterococcus genus are widely distributed in nature. Its strains have been extensively reported to be present in plant surfaces, soil, water and food. In an attempt to assess their potential application in food industry, four Enterococcus faecium group-strains recently isolated from Argentinean regional cheese products were evaluated using a combination of whole genome analyses and in vivo assays. In order to identify these microorganisms at species level, in silico analyses using their newly reported sequences were conducted. The average nucleotide identity (ANI), in silico DNA-DNA hybridization, and phylogenomic trees constructed using core genome data allowed IQ110, GM70 and GM75 strains to be classified as E. faecium while IQ23 strain was identified as E. durans. Besides their common origin, the strains showed differences in their genetic structure and mobile genetic element content. Furthermore, it was possible to determine the absence or presence of specific...
International journal of food microbiology, Jan 14, 2015
Enterococcus is one of the most controversial genera belonging to Lactic Acid Bacteria. Research ... more Enterococcus is one of the most controversial genera belonging to Lactic Acid Bacteria. Research involving this microorganism reflects its dual behavior as regards its safety. Although it has also been associated to nosocomial infections, natural occurrence of Enterococcus faecium in food contributes to the final quality of cheese. This bacterium is capable of fermenting citrate, which is metabolized to pyruvate and finally derives in the production of the aroma compounds diacetyl, acetoin and 2,3 butanediol. Citrate metabolism was studied in E. faecium but no data about genes related to these pathways have been described. A bioinformatic approach allowed us to differentiate cit(-) (no citrate metabolism genes) from cit(+) strains in E. faecium. Furthermore, we could classify them according to genes encoding for the transcriptional regulator, the oxaloacetate decarboxylase and the citrate transporter. Thus we defined type I organization having CitI regulator (DeoR family), CitM cyto...
Uploads
Papers by Christian Magni