Staff member

Maria del Mar Cendra Gascón

Postdoctoral Researcher
Bacterial Infections: Antimicrobial Therapies
+34 934 034 678
Staff member publications

Campo-Pérez, Víctor, Cendra, Maria del Mar, Julián, Esther, Torrents, Eduard, (2021). Easily applicable modifications to electroporation conditions improve the transformation efficiency rates for rough morphotypes of fast-growing mycobacteria New Biotechnology 63, 10-18

Electroporation is the most widely used and efficient method to transform mycobacteria. Through this technique, fast- and slow-growing mycobacteria with smooth and rough morphotypes have been successfully transformed. However, transformation efficiencies differ widely between species and strains. In this study, the smooth and rough morphotypes of Mycobacteroides abscessus and Mycolicibacterium brumae were used to improve current electroporation procedures for fast-growing rough mycobacteria. The focus was on minimizing three well-known and challenging limitations: the mycobacterial restriction-modification systems, which degrade foreign DNA; clump formation of electrocompetent cells before electroporation; and electrical discharges during pulse delivery, which were reduced by using salt-free DNA solution. Herein, different strategies are presented that successfully address these three limitations and clearly improve the electroporation efficiencies over the current procedures. The results demonstrated that combining the developed strategies during electroporation is highly recommended for the transformation of fast-growing rough mycobacteria.

Keywords: Mycobacteria, Clump, Desalted DNA, Electroporation

Moya-Andérico, L., Vukomanovic, M., Cendra, M. D. M., Segura-Feliu, M., Gil, V., del Río, J. A., Torrents, E., (2021). Utility of Galleria mellonella larvae for evaluating nanoparticle toxicology Chemosphere 266

The use of nanoparticles in consumer products is currently on the rise, so it is important to have reliable methods to predict any associated toxicity effects. Traditional in vitro assays fail to mimic true physiological responses of living organisms against nanoparticles whereas murine in vivo models are costly and ethically controversial. For these reasons, this study aimed to evaluate the efficacy of Galleria mellonella as an alternative, non-rodent in vivo model for examining nanoparticle toxicity. Silver, selenium, and functionalized gold nanoparticles were synthesized, and their toxicity was assessed in G. mellonella larvae. The degree of acute toxicity effects caused by each type of NP was efficiently detected by an array of indicators within the larvae: LD50 calculation, hemocyte proliferation, NP distribution, behavioral changes, and histological alterations. G. mellonella larvae are proposed as a nanotoxicological model that can be used as a bridge between in vitro and in vivo murine assays in order to obtain better predictions of NP toxicity. © 2020 Elsevier Ltd

Keywords: Galleria mellonella, Hemocytes, Nanoparticles, Nanotoxicity, Non-rodent in vivo model, Toxicity screening

Cendra, Maria del Mar, Blanco-Cabra, Núria, Pedraz, Lucas, Torrents, Eduard, (2019). Optimal environmental and culture conditions allow the in vitro coexistence of Pseudomonas aeruginosa and Staphylococcus aureus in stable biofilms Scientific Reports 9, (1), 16284

The coexistence between species that occurs in some infections remains hard to achieve in vitro since bacterial fitness differences eventually lead to a single organism dominating the mixed culture. Pseudomonas aeruginosa and Staphylococcus aureus are major pathogens found growing together in biofilms in disease-affected lungs or wounds. Herein, we tested and analyzed different culture media, additives and environmental conditions to support P. aeruginosa and S. aureus coexistence in vitro. We have unraveled the potential of DMEM to support the growth of these two organisms in mature cocultured biofilms (three days old) in an environment that dampens the pH rise. Our conditions use equal initial inoculation ratios of both strains and allow the stable formation of separate S. aureus microcolonies that grow embedded in a P. aeruginosa biofilm, as well as S. aureus biofilm overgrowth when bovine serum albumin is added to the system. Remarkably, we also found that S. aureus survival is strictly dependent on a well-characterized phenomenon of oxygen stratification present in the coculture biofilm. An analysis of differential tolerance to gentamicin and ciprofloxacin treatment, depending on whether P. aeruginosa and S. aureus were growing in mono- or coculture biofilms, was used to validate our in vitro coculture conditions.

Keywords: Applied microbiology, Biofilms

Dreux, Nicolas, Cendra, Maria del Mar, Massier, Sébastien, Darfeuille-Michaud, Arlette, Barnich, Nicolas, Torrents, Eduard, (2015). Ribonucleotide reductase NrdR as a novel regulator for motility and chemotaxis during adherent-invasive Escherichia coli infection Infection and Immunity , 83, (4), 1305-1317

A critical step in the life cycle of all organisms is the duplication of the genetic material during cell division. Ribonucleotide reductases (RNRs) are essential enzymes for this step because they control the de novo production of the deoxyribonucleotides required for DNA synthesis and repair. Enterobacteriaceae have three functional classes of RNRs (Ia, Ib and III), which are transcribed from separate operons and encoded, respectively by the genes nrdAB, nrdHIEF and nrdDG. Here, we investigated the role of RNRs in the virulence of adherent-invasive E. coli (AIEC) isolated from Crohn's disease (CD) patients. Interestingly, the LF82 strain of AIEC harbors four different RNRs (two class Ia, one class Ib and one class III). Although the E. coli RNR enzymes have been extensively characterized both biochemically and enzymatically, little is known about their roles during bacterial infection. We found that RNR expression was modified in AIEC LF82 bacteria during cell infection, suggesting that RNRs play an important role in AIEC virulence. Knockout of the nrdR and nrdD genes, which encodes a transcriptional regulator of RNRs and class III anaerobic RNR respectively, decreased AIEC LF82's ability to colonize the gut mucosa of transgenic mice that express human CEACAM6 (carcinoembryonic antigen-related cell-adhesion molecule 6). Microarray experiments demonstrated that NrdR plays an indirect role in AIEC virulence by interfering with bacterial motility and chemotaxis. Thus, the development of drugs targeting RNR classes, in particular NrdR and NrdD, could be a promising new strategy to control gut colonization by AIEC bacteria in CD patients.

Cendra, M. M., Torrents, E., (2014). Enzims essencials per a la vida Treballs de la Societat Catalana de Biologia , 65, 64-67

Les ribonucleòtid-reductases (RNR) són enzims essencials per a tota cèllula, perquè fan la transformació dels ribonucleòtids a desoxiribonucleòtids, els quals són necessaris per a la síntesi de l’àcid desoxiribonucleic (DNA). És evident que les RNR són enzims ancestrals i clau en l’evolució del material genètic que hi ha actualment, i són essencials per a l’evolució de tots els organismes que hi ha sobre la Terra. A causa de l’essencialitat de la reacció que fan aquests enzims, es poden considerar una diana ideal per al disseny de compostos que inhibeixen la replicació cel·lular, ja sigui en cèl·lules eucariòtiques (incloent-hi cèl·lules cancerígenes), com agents bacterians infecciosos.

Cendra, M. M., Juárez, A., Madrid, C., Torrents, E., (2013). H-NS is a novel transcriptional modulator of the ribonucleotide reductase genes in escherichia coli Journal of Bacteriology , 195, (18), 4255-4263

Ribonucleotide reductases (RNRs) are essential enzymes for DNA synthesis because they are responsible for the production of the four deoxyribonucleotides (dNTPs) from their corresponding ribonucleotides. Escherichia coli contains two classes of aerobic RNRs, encoded by the nrdAB (class Ia) and nrdHIEF (class Ib) operons, and a third RNR class, which is functional under anaerobic conditions and is encoded by the nrdDG (class III) operon. Because cellular imbalances in the amounts of the four dNTPs cause an increase in the rate of mutagenesis, the activity and the expression of RNRs must be tightly regulated during bacterial chromosome replication. The transcriptional regulation of these genes requires several transcription factors (including DnaA, IciA, FIS [factor for inversion stimulation], Fnr, Fur, and NrdR), depending on the RNR class; however, the factors that dictate the expression of some RNR genes in response to different environmental conditions are not known. We show that H-NS modulates the expression of the nrdAB and nrdDG operons. H-NS represses expression both in aerobically and in anaerobically growing cells. Under aerobic conditions, repression occurs at the exponential phase of growth as well as at the transition from the exponential to the stationary phase, a period when no dNTPs are needed. Under anoxic conditions, repression occurs mainly in exponentially growing cells. Electrophoretic mobility assays performed with two DNA fragments from the regulatory region of the nrdAB operon demonstrated the direct interaction of H-NS with these sequences.

Cendra, M. d M., Juárez, A., Torrents, E., (2012). Biofilm modifies expression of ribonucleotide reductase genes in Escherichia coli PLoS ONE 7, (9), e46350

Ribonucleotide reductase (RNR) is an essential enzyme for all living organisms since is the responsible for the last step in the synthesis of the four deoxyribonucleotides (dNTPs) necessary for DNA replication and repair. In this work, we have investigated the expression of the three-RNR classes (Ia, Ib and III) during Escherichia coli biofilm formation. We show the temporal and spatial importance of class Ib and III RNRs during this process in two different E. coli wild-type strains, the commensal MG1655 and the enteropathogenic and virulent E2348/69, the prototype for the enteropathogenic E. coli (EPEC). We have established that class Ib RNR, so far considered cryptic, play and important role during biofilm formation. The implication of this RNR class under the specific growth conditions of biofilm formation is discussed.

Garcia, J., Madrid, C., Cendra, M., Juarez, A., Pons, M., (2009). N9L and L9N mutations toggle Hha binding and hemolysin regulation by Escherichia coli and Vibrio cholerae H-NS FEBS Letters , 583, (17), 2911-2916

Proteins of the Hha/YmoA family co-regulate with H-NS the expression of virulence factors in Enterobacteriaceae. Vibrio cholerae lacks Hha-like proteins and its H-NS (vcH-NS) is unable to bind Hha, in spite of the conservation of a key residue for Hha binding by Escherichia coli H-NS (ecH-NS). Exchange of the residues in position 9 between vcH-NS and ecH-NS strongly reduces Hha binding by ecH-NS and introduces it in vcH- NS. These mutations strongly affect the repression of the hemolysin operon in E. coli and the electrophoretic mobility of complexes formed with a DNA fragment containing its regulatory region.

Keywords: Nucleoid associated protein, H-NS, Hha, Transcription repression, NMR, Electrophoretic mobility shift assays