Sumario
 Título / Autor(es)Página(s)
[R]Mechanisms of resistance to Qo. Fungicides in phytopathogenic fungi. / Fernández-Ortuño, Dolores / Torés, Juan. A. / de Vicente, Antonio / Pérez-García, Alejandro.
Summary. The major threat to crops posed by fungal diseases results in the use by growers of enormous amounts of chemicals. Of these, quinol oxydation inhibitors (QoIs) are probably the most successful class of agricultural fungicides. QoIs inhibit mitochondrial respiration in fungi by binding to the Qo site ofthe cytochrome bc] complex, blocking electron transfer and halting ATP synthesis. Unfortunately, the rapid development of resistance to these fungicides and consequent control failure has become increasingly problematic. The main mechanism conferring resistance to QoIs is target site mod¬ification, involving mutations in the cytochrome b gene CYTB, such as the substitution of glycine by alanine at position 143 (G143A) that occurs in several phytopathogenic fungi. The impact of other mechanisms, including alternative respiration and efflux transporters, on resistance seems to be limited. Interestingly, in some species QoI resistance is not supported by mutations in CYTB, while in others the structure ofthe gene is such that it is unlikely to undergo G l43A mutations. Better understanding of the biological basis of QoI resistance in a single pathogen species will facilitate the development of resist¬ance diagnostic tools as well as proper anti-resistance strategies aimed at maintaining the high efficacy of these fungicides. [Int Microbiol 2008; 11 (1): 1-9]
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[R]Modeling the combined effects of enterocins A and B, lactate, and EDTA on the growth of Salmanella at different temperatures. / Bover-Cid, Sara. / Jofré, Anna. / Ayrnerich, Teresa. / Garriga, Margarita.
Summary. The effects of enterocins A and B (produced by Enterococcus faecium CTC492), lactate, and ethylenediaminetetraacetic acid (EDTA) on the growth of Salmonella were modeled together with temperature using the response surface methodology. Six serovars of Salmonella enterica were inoculated (ca. 103 cells/ml) in brain-heart infusion broth with different levels of the studied factors and then incubated at different temperatures. The results showed that while Salmonella growth was affected by all the factors, temperature was the most important factor influencing the time to detection of the paihogen. All factors, including temperature, showed significant two-way interactions. The presence of enterocins A and B, lactate, and EDTA had an inhibitory effect that was enhanced at suboptimal temperatures for growth, thus delaying the time to detection. Moderate-low concentrations of lactate and EDTA increased the inhibitory effect of enterocins A and B. The effectiveness ofthese bacteriocins was not further enhanced by high concentrations oflactate (>3.6%) or EDTA (>200 mg/l). The mathematical model obtained from these analyses provides a useful tool to assess the effects of natural antimicrobials and their interactions with other growth-related factors on the growth response of Salmonella. The results can be applied to determine the most effective combination of hurdles to be used in the preservation of food products. [Int Microbiol 2008; 11(1): 11-16]
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[R]Heterologous protective immunization elicited in mice by Pasteurella multocida fur ompH. / Garrido, M. Elena / Bosch, Montserrat. / Bigas, Anna. / Badiola, Ignacio. / Barbé, Jordi. / Llagostera, Montserrat.
Summary. Different strategies have been developed to produce vaccines against Pasteurella multocida. The approach described herein involves overexpression on the bacterial cell surface of Fur-regulated IROMPs (iron-regulated outer-membrane proteins). Accordingly, the ability offur mutants to promote heterologous protection was examined in a Swiss mouse animal model. Two fur mutants derived from P multocida were isolated, one of which was also defective in the OmpH protein. In mice challenged with virulent P multocida, outer-membrane protein (OMP) extracts offur cells conferred the same protection as obtained with wild-type cells grown in iron-depleted medium. Total protection was achieved with 40 /lg ofOMP extract from the fur ompH mutant. Mice administered heat-inactivated fur ompH cells were 60% cross-protectéd. The presence of a galE mutation in these cells did not further increase the protection level. Additionally, cell disruption by sonication provoked a higher level of protection than conferred by heat-treated cells. Taken together, the results showed that P multocida fur ompH cells offer a simple and suitable approach for cross-protecting animals against infection with P multocida. [Int Microbio12008; 11(1): 17-24]
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[R]Influence of a Streptomyces lividans SecG functional analogue on protein secretion. / Palomino, Carmen. / Mellado, Rafael. P.
Summary. The membrane protein complex translocase mediates the translocation of bacterial proteins. In this complex, the Sec Y, SecE, and SecG proteins constitute an integral membrane domain. Sequence comparison revealed a potential secG¬like gene in the gram-positive soil bacterium Streptomyces lividans. Chromosomal deletion of this gene resulted in a sporulation defect and an overall deficiency in secretion. The SecG-depleted strain was able to overproduce and secrete a-amylase, but the appearance ofthe oversynthesized protein outside the cell was delayed compared to the protein produced by the wildtype strain. SecG deficiency was found to result in more pronounced effects in S. Lividans than in Bacillus subtilis or Escherichia coli. [Int Microbiol 2008; 11 (1): 25-31]
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[R]Value of recN sequences for species identification and as a phylogenetic markerwithin the family 11 Leuconostocaceae". / Arabal, David. R. / Sanchez, Ester. / Macián, M. Carmen. / Garay, Esperanza.
Summary. The genera Leuconostoc, Oenococcus, and Weissella (family "Leuconostocaceae") constitute a group oflactic acid bacteria of great interest in food microbiology. From the taxonomic point of view, they are considered phylogenetically coherent according to their 16S rRNA gene sequences and other macromolecules. These three genera were the focus of the present study; specifically, the resolution and discriminatory power of recN (encoding a DNA repair and genetic recombination protein) as a molecular marker at the species level were investigated. For this purpose, partial sequences (about 1200 nt) were obtained from 23 type strains and from several additional strains following direct amplification of recN and subsequent sequencing. Phylogeny was evaluated according to different treeing methods (neighbor joining, maximum likelihood, and maximum parsimony) and the inclusion ofvariability filters. The results showed that recN, used either alone or in combination with 16S rRNA data, can serve as a phylogenetic marker as well as a tool for species identification. (Int Microbiol 2008; 1l(1): 33-39]
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[R]Massive presence of insertion sequences in the genome of SOPE, the primary endosymbiont of the rice weevil Sitophilus oryzae. / Gil, Rosario. / Belda, Eugeni. / Gosalbes, María J. / Delaye, Luis. / Vallier, Agnes. / Vincent-Monégat, Carole. / Heddi, Abdelaziz. / Silva, Francisco J. / Moya, Andrés. / Latorre, Amparo.
Summary. Bacteria that establish an obligate intracellular relationship with eukaryotic hosts undergo an evolutionary genomic reductive process. Recent studies have shown an increase in the number of mobile elements in the first stage of the adaptive process towards intracellular life, although these elements are absent in ancient endosymbionts. Rere, the genome of SOPE, the obligate mutualistic endosymbiont of rice weevils, was used as a model to analyze the initial events that occur after symbiotic integration. During the first phases of the SOPE genome project, four different types of insertion sequence (IS) elements, belonging to well-characterized IS families from y-proteobacteria, were identified. In the present study, these elements, which may represent more than 20% of the complete genome, were completely characterized; their relevance as a source of gene inactivation, chromosomal rearrangements, and as participants in the genome reductive process are discussed herein. [Iot Microbiol 2008; 11 (1): 41-48]
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[R]Fumarate and nitrate reduction (FNR) dependent activation of the Escherichia coli anaerobic ribonucleotide reductase nrdDG promoter. / Roca, Ignasi. / Ballana, Ester. / Panosa, Anais. / Torrents, Eduard. / Gibert, Isidre.
Summary. The nrdDG promoter regulates transcriptional expression of the anaerobic ribonucleotide reductase of Escherichia coli, an essential enzyme required to supply the building blocks for DNA synthesis. In this work, binding ofthe pleiotropic FNR ([umarate and nitrate reduction) transcriptional regulator to the nrdDG promoter region and the effects of binding on transcription were investigated. Gel retardation analysis with purified FNR * demonstrated FNR interaction at two FNR sites, terrned FNR-2 and FNR-l, while studies with altered FNR boxes indicated that the upstream FNR-2 site was essential for anaerobic activation of the nrdDG promoter. Although the FNR-l site was not absolutely required, it allowed maximal expression of this promoter. These results suggest that the two sites have an additive effect in coordinating nrdDG expression in response to shifting oxygen concentrations. [Int Microbio) 2008; 11(1): 49-56]
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[R]Saccharomyces cerevisiae Rds2 transcription factor involvement in cell wall composition and architecture. / Moreno, Inmaculada. / Tutrone, Nunzia. / Sentandreu, Rafael. / Valentín, Eulogio.
Summary. Although the cell wall is very important in yeasts, relatively little is known about the relationship between its structure and function. In Saccharomyces cerevisiae, a family of 55 transcription factor proteins unique to fungi, so-called zinc cluster proteins, has been described. Of these, Rds2 has been identified as an activator/inhibitor of gluconeogenesis. However, previous studies have pointed out additional roles for this protein, specifically, in the modulation of cell-wall architecture and drug sensitivity. In this work, evidence regarding the role ofRds2 as a regulator of cell-wall architecture and composition is presented based on phenotypical analysis of the cell walls prepared ITom a S. Cerevisiae Rds2 niutant strain. Analyses ofthe sensitivity ofthis rds2¡j mutant to different drugs and to osmotic stress showed that Rds2 is indeed involved in the drug-sensitivity response and plays a role in determining osmotic sensitivity. [Int Microbio12008; 11(1): 57-63]
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