Typical metabolic traits of two Oenococcus oeni strains isolated from Valpolicella wines

AIMS

Physiological comparison of two indigenous Oenococcus oeni strains, U1 and F3 isolated in the same area (Valpolicella, Italy) in order to select a performant starter for MLF in wine.

METHODS AND RESULTS

Growth rate, sugar and malate metabolism in FT80 media at pH 5.3 and 3.5 were analysed. The amount of total protein synthesized and the level of expression of the small Hsp Lo18 were evaluated by radiolabelling and immunodetection experiments after heat (42 degrees C), acid (pH 3.5) and ethanol (12% v/v) stresses. Strain U1 showed significantly lower specific growth rate and growth yield in acid conditions than strain F3. However, strain U1 had a higher malate consumption capacity at pH 3.5 than strain F3, in relation with an higher malolactic activity determined on whole cells. Strain U1 exhibited about half the total protein synthesis level than strain F3, but both strains expressed Lo18 similarly. Evaluation of malolactic fermentation (MLF) performance by microvinification trials was carried out. Strain U1 was able to complete MLF, whereas strain F3 degraded malic acid partially when inoculated in Amarone wine.

CONCLUSIONS

Considering its performances in microvinifications experiments, strain U1 could be a good candidate for malolactic starter as an alternative to deficient commercial starters.

Reclassification of Leuconostoc argentinum as a later synonym of Leuconostoc lactis

Leuconostoc argentinum, Leuconostoc lactis and ten related strains from Romanian dairy products formed a single cluster, clearly separated from other Leuconostoc species, after numerical analysis of repetitive extragenic palindromic-PCR patterns, whole-cell protein profiles (SDS-PAGE) and fluorescent amplified fragment length polymorphism (FAFLP) band patterns. 16S rRNA gene sequence analysis confirmed a very high similarity between both type strains and representative dairy isolates (>99.6 %). DNA-DNA hybridization experiments revealed high relatedness values between the type strains of L. argentinum and L. lactis and between these strains and representative Romanian strains. These data and the lack of phenotypic distinctive characteristics demonstrate that L. argentinum and L. lactis are synonymous.

Growth modelling of Listeria monocytogenes and Yersinia enterocolitica in food model systems and dairy products

The growth potential of Listeria monocytogenes, measured with a gaschromatographic method, was evaluated in model systems simulating dairy products in which NaCl concentration, pH and lipid concentration ranged from values corresponding to matured hard cheeses to some light cheeses and other dairy products. The growth data from the model systems, calculated on the basis of the polynomial models obtained, were compared with values observed for dairy products. Growth parameters of Yersinia enterocolitica in traditional and light cheeses were also available. The comparison between predicted and observed data suggested that individual or interactive effects of chemicophysical variables such as pH, salt and lipid concentration are not sufficient to predict the fate of L. monocytogenes in dairy products. Microstructural factors as well as the pH effect on water binding capacity of proteins could also be implicated.

Reclassification of Lactobacillus thermotolerans Niamsup et al. 2003 as a later synonym of Lactobacillus ingluviei Baele et al. 2003

The relatedness of the speciesLactobacillus ingluvieiandLactobacillus thermotoleranswas investigated by comparing partial sequences of the 16S rRNA gene (99·9 % similarity over 1504 bp), thehsp60gene (98·8 % similarity over 954 bp) and therecAgene (98·5 % similarity over 452 bp) and by determining DNA–DNA binding levels (79±3 %) and genomic DNA G+C contents (50 and 49 mol%, respectively). These data, in addition to their similar biochemical characteristics, suggest that the two taxa constitute a single species. According to Rules 38 and 42 of theBacteriological Code, they should be united under the nameLactobacillus ingluviei, with the nameLactobacillus thermotoleransas a later heterotypic synonym.

Amarone: a modern wine coming from an ancient production technology

Amarone wine is a renowned dry red wine produced in Valpolicella (Verona, Northern Italy). It is made from local grapes varieties (Corvina, Rondinella, and Molinara) that are slowly dried under natural conditions during the fall into winter. After the postharvest drying, carried out for several weeks in dedicated lofts called fruttaio, the grapes are vinified: crushed, given prefermentative cold maceration, undergo alcoholic fermentation on the skins, malolactic fermentation, and finally maturation. The partially dried grapes are traditionally crushed during the second half of January to February. Because cellar conditions are unfavorable for either alcohol or malolactic fermentation, selected microbial cultures (yeasts and malolactic bacteria) are often necessary to correctly manage fermentation. The progress of both fermentation processes needs constant surveillance. During maturation conducted in vessels or wooden containers (tonneau in durmast oak), clarification and stabilization lead to improvements in quality. Product specifications require that Amarone not be bottled before the wine has been aged for 2years (Anonymous (2010). Disciplinare di produzione dei vini a denominazione di Origine Controllata e Garantita "Amarone della Valpolicella". Gazzetta Ufficiale della Repubblica Italiana. Serie generale n. 84. April 12). Amarone achieved its DOCG (Controlled and Guaranteed Denomination) status in 2010.

Development of the Specific and Random Amplification (SARA)-PCR for both species identification of enterococci and detection of the vanA gene

A rapid and reliable polymerase chain reaction (Specific and Random Amplification (SARA)-PCR) has been developed to identify enterococcal species and to detect the vanA gene in one single reaction. This technique was based on the use of the primer set previously designed to amplify a part of the vanA gene (Dutka-Malen et al., J. Clin. Microbiol., 33 (1995) 24-27). In the chosen low stringency conditions complex patterns were obtained, with a sharp band of approximately 700 bp in cases where the vanA gene was present. Discrimination at the species and strain level was achieved by applying the SARA-PCR assay to a collection of 55 enterococcal isolates and type strains. Simultaneously the vanA gene was detected in all strains showing high resistance to vancomycin.

Should names reflect the evolution of bacterial species?

Systematics is the process of characterizing and arranging bacterial diversity in an orderly manner, recognizing groups of similar organisms in a hierarchical scheme whose basic entity is the species. To allow the exchange of scientific knowledge, taxa have to be named. Taxa are not static entities since they are subject to evolution, the direction of which can be inferred by using a wide range of techniques targeting specific traits. However, it is not clear how this dynamism should be reflected in taxonomic nomenclature. In the present report, several considerations are presented that deal with the relationship between the evolution of taxa and their nomenclature; an example is given which concerns the nomenclature of the species Lactobacillus delbrueckii.

The status of the species Lactobacillus rogosae Holdeman and Moore 1974. Request for an Opinion

A brief history of the species Lactobacillus rogosae is presented. It was ascertained that the type strain and other existing strains are not available in any established culture collection; therefore, they cannot be included in any scientific study. This matter is referred to the Judicial Commission, asking for an Opinion on the status of the species.

Taxonomy of Lactobacilli and Bifidobacteria

Genera Lactobacillus and Bifidobacterium include a large number of species and strains exhibiting important properties in an applied context, especially in the area of food and probiotics. An updated list of species belonging to those two genera, their phylogenetic relationships and other relevant taxonomic information are reviewed in this paper. The conventional nature of taxonomy is explained and some basic concepts and terms will be presented for readers not familiar with this important and fast-evolving area, which importance is often underestimated. The analysis of biodiversity and its cataloguing, i.e. taxonomy, constitute the basis for applications and scientific communication: reliable identification and correct naming of bacterial strains are not only primary aims of taxonomic studies, but also fundamental elements in an applied context, for the tracking of probiotic strains and a non fraudulent labelling of fermented milks and pharmaceutical products containing probiotic microorganisms. A number of resources freely available have been listed and their use is suggested for people concerned with different aspects of taxonomy. Some perspectives in taxonomy have been outlined, in particular considering the role of culture independent analyses to reveal the still unknown and uncultured microorganisms. Finally, the impact of the availability of whole-genome sequences in taxonomy is briefly explained: they have already begun to give insights on bacterial evolution, which will surely have implications on taxonomy, even if the analysis of data for lactic acid bacteria is still limited to few species.

Identification of vaginal lactobacilli from asymptomatic women

In the present work, carried out by means of phenotypic and genotypic tests, it has been demonstrated that none of the vaginal lactobacilli isolated from asymptomatic women were genetically close to L. acidophilus ATCC 4356. Strains of homofermentative lactobacilli were identified as Lactobacillus gasseri, L. jensenii and L. crispatus, while in the heterofermentative only one strain was classified as L. fermentum. Moreover a genetically homologous group of heterofermentative lactobacilli, that could represent a new species, were evidenced.

Colonization of a human intestine by four different genotypes of Lactobacillus acidophilus

To understand the effect on a human host suffering from intestinal disorders we supplied non fat milk cultures of Lactobacillus acidophilus for 25 days. The picture of the faeces bacterial count was completely different before and after treatment and we noticed increases in lactobacilli, bifidobacteria and coliforms while the clostridia decreased. The lactobacilli treatment solved the diarrohea problem. Of the four genetic lines of L. acidophilus supplied only D179, isolated from calf faeces, and ATCC 4356 of human origin were found able to colonize the intestine of the little girl, while 255S isolated from swine and D328 isolated from calf faeces, did not find favourable growth conditions.

Lactobacillus lactis as dominant lactobacilli flora in human intestine

The presence of Lactobacillus lactis, as a dominant lactic acid microflora, has been demonstrated in human feces by means of phenotypic and genotypic tests. This unusual fecal bacteria allows some considerations on the ubiquity and environmental specificity of the lactobacilli.

A novel bioengineering clinical device testing cellular homeostatic potentials to customize and monitor nutritional-related age-management interventional strategies

Most devices assessing body composition harbor a number of drawbacks and hardly assess the phenomena taking place at a cellular membrane level. The present single-frequency bioelectrical potential homeostatic structure analysis (PHoSA) technology requires only a proper hands contact on fixed electrodes and determines the phase displacement between tested current and voltage by using a 50-KHz alternate sinusoidal current. This allows quick testing time with high degree of precision, sensitivity, and specificity of sectorial functional body compartments analysis. Such assessment may prove to be an integrated part of either a diagnostic workup or monitoring tool in tailoring nutritional/nutraceutical, pharmacological, and exercise activity, all being framed within a proactive, preventive, age-intervention management strategy.