2,241 research outputs found
Noncanonical sortase-mediated assembly of pilus type 2b in group B Streptococcus
No full textGroup B Streptococcus (GBS) expresses 3 structurally distinct pilus types (1, 2a, and 2b) identified as important virulence factors and vaccine targets. These pili are heterotrimeric polymers, covalently assembled on the cell wall by sortase (Srt) enzymes. We investigated the pilus-2b biogenesis mechanism by using a multidisciplinary approach integrating genetic, biochemical, and structural studies to dissect the role of the 2 pilus-2b-associated Srts. We show that only 1 sortase (SrtC1-2b) is responsible for pilus protein polymerization, whereas the second one (Srt2-2b) does not act as a pilin polymerase, but similarly to the housekeeping class A Srt (SrtA), it is involved in cell-wall pilus anchoring by targeting the minor ancillary subunit. Based on its function and sequence features, Srt2-2b does not belong to class C Srts (SrtCs), nor is it a canonical member of any other known family of Srts. We also report the crystal structure of SrtC1-2b at 1.9 Å resolution. The overall fold resembles the typical structure of SrtCs except for the N-terminal lid region that appears in an open conformation displaced from the active site. Our findings reveal that GBS pilus type 2b biogenesis differs significantly from the current model of pilus assembly in gram-positive pathogens.-Lazzarin, M., Cozzi, R., Malito, E., Martinelli, M., D'Onofrio, M., Maione, D., Margarit, I., and Rinaudo, C. D. Noncanonical sortase-mediated assembly of pilus type 2b in group B Streptococcus
Structure analysis and site-directed mutagenesis of defined key residues and motives for pilus-related sortase C1 in group B Streptococcus
No full textIn group B Streptococcus (GBS), 3 structurally distinct types of pili have been discovered as potential virulence factors and vaccine candidates. The pilus-forming proteins are assembled into high-molecular-weight polymers via a transpeptidation mechanism mediated by specific class C sortases. Using a multidisciplinary approach including bioinformatics, structural and biochemical studies, and in vivo mutagenesis, we performed a broad characterization of GBS sortase C1 of pilus island 2a. The high-resolution X-ray structure of the enzyme revealed that the active site, into the β-barrel core of the enzyme, is made of the catalytic triad His157-Cys219-Arg228 and covered by a loop, known as the “lid.” We show that the catalytic triad and the predicted N- and C-terminal transmembrane regions are required for the enzyme activity. Interestingly, by in vivo complementation mutagenesis studies, we found that the deletion of the entire lid loop or mutations in specific lid key residues had no effect on catalytic activity of the enzyme. In addition, kinetic characterizations of recombinant enzymes indicate that the lid mutants can still recognize and cleave the substrate-mimicking peptide at least as well as the wild-type protein.—Cozzi, R., Malito, E., Nuccitelli, A., D’Onofrio, M., Martinelli, M., Ferlenghi, I., Grandi, G., Telford, J. L., Maione, D., Rinaudo, C. D. Structure analysis and site-directed mutagenesis of defined key residues and motives for pilus-related sortase C1 in group B Streptococcus
Spore di muffe e di Ustilago maydis in farine di mais : dati sperimentali e considerazioni igienico-sanitarie
No full textIsolamento di Burkholderia cepacia da prodotti lattiero caseari
No full textBatteri del genere Burkholderia sono organismi isolabili da numerosi siti ecologici. Questi batteri esercitano compiti di biocontrollo, biomediazione e favoriscono la crescita di vegetali. Possono uscire patogeni in particolare condizione e anche alterare i prodotti lattiero-caseari. In questo lavoro viene descritta una contaminazione di lattici da B. cepacia ed è riportata la sistematica dei ceppi appartenenti al genere
Dati sull'eventuale presenza di Ocratossina A in salumi
No full textUsing two different techniques of analysis it has been impossible to evidence the Ochratoxin A presence in Italian salami
Impacts of Wildlife on Agriculture: A Spatial-Based Analysis and Economic Assessment for Reducing Damage
No full textOver the last few years, the impacts of wildlife on agriculture have constantly been growing, in particular in areas close to woodland and in hunting ban zones (“refuge effect”). Public administrations have difficulty in meeting the growing requests for crop damage compensation. The development of appropriate measures to control this trend—starting from the understanding of the dynamics concerned—is crucial. The aim of this study was, therefore, to analyze damage at regional scale and define common local actions. In particular, the study involved different steps that define a spatial-based classification of risk levels, integrating statistical methods (principal component analysis and receiver operating characteristic) with multi-criteria evaluation (MCE) in a geographic information system (GIS). It turns out that, in the study area, the very high-risk zones affect 8.83% of used agricultural areas; about 97% of them concentrated in the first 400 m from the most suitable habitats. A selected cluster of 11 test areas within these zones allowed us to assess the cost-effectiveness of integrated prevention and control actions (IPCA) with respect to the compensation of the damage. The analysis shows cost of IPCA to be nearly twice the actual cost incurred by the public administration to compensate partially the damage. The comparison with the estimated damage shows the overall economic convenience of the proposed investment with significant differences depending on the areas. Thus, we suggest reaching an “agro-ecological” balance starting from actions on specific areas; if they produce the desired effects, they could be progressively extended to other areas with gradual investments (adaptive management)
Batteri pigmentati del Taleggio
No full textSome pigmented bacteria which are present on the surfaces of Taleggio cheese have been isolated and identified. They are Arthrobacter spp., Corynebacterium spp., Microbacterium, Brevibacterium linens, and Staphylococcus spp. The media of their isolation have been described
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