1,721,012 research outputs found
Genotypic typing of bacterial ecotypes significantly present in natural fermentation of italian dairy products
No full textThis PhD thesis dealt with the phenotypic and genotypic characterization of LAB strains through a polyphasic taxonomic approach, molecular analyses such as PCR, ITS, ARDRA, the study of housekeeping genes, search and classification of extracromosomal DNA. The integration of the phenotypic, biotechnological and genotypic results allowed the obtainment of fingerprinting specific at the strain-level and the possible discrimination of the strains in function of their ecological niches
The nematode Caenorhabditis elegans as an innovative tool for studying foodborne metabolites and emerging pathogens in the food industry
No full textIn the last few decades, various epidemiological evidence has reinforced the concept that diet plays an important role in human health, showing that the type, composition and amount of food consumed can all be linked to the promotion and/or maintenance of a healthy state of being. Traditional fermented functional foods are increasingly being considered healthy and interest in their nutritional and health impact, as well as demand for them, is continuously increasing. Their health benefits are linked to functional microorganisms. These microorganisms may contribute to food functionality exerting a biogenic effect due to the release of active metabolites and bioactive compounds during food processing. Fermented foods are complex and dynamic systems in which microbial populations interact. The technology for production and conservation of foods can influence the development or
inhibition of specific bacterial species which are difficult to detect applying the classical microbiological techniques. The nematode Caenorhabditis elegans represents an innovative tool for studying foodborne metabolites and emerging pathogens in the food industry. This free-living nematode provides several practical and experimental advantages, including a short life-cycle, and easy and economic cultivation in large numbers. Some of the characteristics of the C. elegans immune system are conserved in higher eukaryotic organisms. Together with high-performance functional metagenomic and metabolomic analyses, this nematode represents a good model to investigate the potential adverse effects of food-derived microbial bioactive compounds. The information obtained from these studies will open new avenues for the design of innovative biosensors, suitable for specific and rapid
bacterial metabolite detection
Genotypic characterization of non starter lactic acid bacteria involved in the ripening of artisanal Bitto PDO cheese
No full textBitto of Valchiavenna, an artisanal Italian cheese produced without the addition of any starter cultures, has been attributed a protected designation origin (PDO) cheese, but the strain composition of the natural microbial population colonizing this traditional dairy product is still unknown. To obtain preliminary information on the non starter lactic acid bacteria involved in its ripening, a total of 136 NSLAB isolates, randomly selected from MRS and M17 agar plates, were collected from three different cheese samples after 120 days of ripening. The new isolates were identified by combining PCR 16S–23S rDNA spacer analyses, partial 16S rRNA gene sequencing, species-specific probes and colony hybridization. Eighty-two isolates, representing 60% of the total strains selected, were homofermentative cocci: 83% of them were enterococci, with Enterococcus durans being the predominant species found. Pediococcus spp. were also isolated, together with strains of Streptococcus thermophilus. Within lactobacilli, 57% of the isolates were identified as Lactobacillus paracasei; Lact. curvatus, Lact. plantarum, Lact. fermentum, were present in a lower amount. The isolates were differentiated at strain-level by Rep-PCR analysis. This is the first effort to microbiological characterization of Valchiavenna’s Bitto; the results suggest the possibility of preserving the wild bacterial population in order to protect the typical organoleptic characteristics of this traditional raw milk cheese and to select new strains for the dairy industry
A Study of Lactose Metabolism in Lactococcus garvieae Reveals a Genetic Marker for Distinguishing between Dairy and Fish Biotypes
No full textDair y and fish isolates of Lactococcus garvieae were tested for their ability to utilize lactose and to grow in milk. Fish
isolates were unable to assimilate lactose, but unexpectedly, they possessed the ability to grow in milk. Genetic studies, carried
out constructing different vectorette libraries, provided evidence that in fish isolates, no genes involved in lactose utilization were present. For L. garvieae dair y isolates, a single system for the catabolism of lactose was found. It consists of a lactose
transport and hydrolysis depending on a phosphoenolpyruvate-dependent phosphotransferase system combined with a phospho
A genetic marker for Lactococcus garvieae ecotypes
No full textLactococcus garvieae is considered as an emerging pathogen of increasing clinical significance in the fields of fish farming (Eyngor et al. 2004; Kawanishi et al. 2006). It has also been isolated from clinical specimens of human blood, urine and skin, indicating the expanding importance of this bacterium in the fields of veterinary and human medicine. Few reports on pathogenicity of L. garvieae in yellowtails indicate the cell capsule as the most important virulence factor in this species. However, deepened studies on L. garvieae have not been carried out. This is an important point, principally after the detection of L. garvieae in many food products. Particularly, this organism has been isolated in the dairy environment either as nondominant species or as prevalent bacterial population (Fortina et al. 2003). For these reasons, the possibility to discriminate L. garvieae strains on the specific ecological niches is of great practical interest
Multilocus restriction typing : a tool for studying molecular diversity within Lactobacillus helveticus of dairy origin
No full textForty-two Lactobacillus helveticus strains isolated from whey starter cultures and cheeses were typed by multilocus restriction typing (MLRT), analyzing the restriction fragment-length polymorphism of PCR products generated from eight loci of housekeeping genes: b-galactosidase, lactose permease, UDP-galactose-4 epimerase, b-galactosidase transcriptional regulator, D-lactate dehydrogenase, peptidase N, stress-inducible protein and S-layer protein. MLRT analysis evidenced wide strain heterogeneity. Strains were grouped according to their source of isolation. The low infra-species polymorphism detected in the 16S rRNA gene did not enable to group the strains with the same sensitivity reached by MLRT of protein-coding genes. This is the first description of MLRT as a technique for the discrimination of L. helveticus strains; this technique seems a promising tool to evaluate genetic diversity of related strains from different ecological niches
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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