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In the last two decades the application of molecular techniques has had a major impact on the classification of yeasts. The nuclear DNA relatedness has become the basis of species delineation. Molecular fingerprinting methods such as analysis of restriction fragment length polymorphisms, random amplified polymorphic DNA, PCR-amplified sequences and fragments, pulsed field gel electrophoresis of chromosome DNA and others allow intraspecies differentiation and typing. The most far reaching method has been the sequencing of various parts of ribosomal DNA that has made for the first time possible to assess the phylogenetic relationships among yeasts at different taxonomic levels. Based on the molecular data obtained so far several changes have been introduced in the classification of yeasts, however, substantial restructuring of current taxonomic schemes with the consequence of numerous nomenclatural changes must await further studies.

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Current taxonomy of common foodborne bacteria

Part I. Gram-negative phyla of proteobacteria and bacteroidetes

Acta Alimentaria
Author:
T. Deák

Recent changes in classification of the four major groups of cultivable bacteria commonly encountered in foods are reviewed. Newly described species and genera as well as reassignment of former taxa belonging to Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria are considered. Taxonomic changes are surveyed derived from results of 16S rRNA gene analysis confirmed by other molecular techniques and traditional methods. The review is aimed to update relevant taxonomic information for those not directly involved in taxonomy, however, this kind of information will have significance in understanding the microbial ecology of food systems and promote improvement of preservation methods, fermentation technologies as well as enhance the safety of products.

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A survey of current taxonomy of common foodborne bacteria

Part II. Gram-positive phyla of Firmicutes and Actinobacteria

Acta Alimentaria
Author:
T. Deák

Recent changes in classification of the four major groups of cultivable bacteria commonly encountered in foods are reviewed. Newly described species and genera as well as reassignment of former taxa belonging to Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria are considered. Taxonomic changes are derived from results of 16S rRNA gene analysis confirmed by other molecular techniques and traditional methods. The review is aimed to update relevant taxonomic information for those not directly involved in taxonomy, however, this kind of information will have significance in understanding the microbial ecology of food systems and promote improvement of preservation methods, fermentation technologies as well as enhance the safety of products.

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Wine fermentation is a complex microbiological process in which yeasts predominate. It is long debated whether yeasts occurring on the surface of grapes or the resident yeasts on the winery equipment play the primary role in conducting the fermentation. The origin, development, changes and succession of various yeast species can be followed using specific molecular techniques allowing the differentiation and typing of yeast strains. Techniques such as pulsed field gel electrophoresis of chromosomal DNA, restriction fragment length polymorphism analysis, and polymerase chain reaction (PCR)-based methods have recently been employed in studying the microbiology of wine making. These shed new light on the dynamics of fermentation started spontaneously or directed by the inoculation of starter cultures.

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In April 2011 the new 5th edition of “The Yeasts, a Taxonomic Study” was published (Kurtzman et al., 2011). This prompted to give an overview to orientate the interested readers about the substantial changes having carried out in the classification of yeasts since the previous 4th edition (Kurtzman & Fell, 1998). In terms of figures, the number of approved yeast species has increased from about 700 in 93 genera (4th ed.) to about 1500 in 148 genera (5th ed.), and within the overall figures, the ratio of basidiomycetous yeast genera increased from 39% to 42% (Table 1).

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Comparison of eleven selective media for detecting and enumerating foodborne yeasts in blue-veined cheese showed that rose bengal chloramphenicol agar (RBC), dichloran rose bengal chloramphenicol agar (DRBC), oxytetracycline gentamycin glucose yeast extract agar (OGGY) and dichloran 18% glycerol agar (DG18) were the most efficient. Other examined media failed to be suitable for either inhibiting bacteria and suppressing the spread of moulds or supporting the growth of all yeasts present. Significant differences (P≯0.05) were obtained on different media, however counts obtained were overlapping on three groups of media. Yeast extract eugenol agar (YEE) medium significantly differed from all others.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
E. Kuzmann
,
M. Varsányi
,
L. Korecz
,
A. Vértes
,
T. Masumoto
,
F. Deák
,
Á. Kiss
, and
L. Kiss

Abstract  

Neutron, and Mössbauer spectroscopy were used to study the possibility of cold nuclear fusion in Fe90Zr10 amorphous ribbon having high hydrogen absorbing ability. No significant changes in the neutron and in the spectra were found at deuterization performed electrochemically at different cathodic potentials. The observed differences between the Mössbauer spectra of samples deuterized in air and in nitrogen atmosphere can be explained by decrease of deuterium uptake as well as by a small heat effect due to reaction of hydrogen with oxygen dissolved in water in the case of electrolysis carried out in air.

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We studied the early vegetation dynamics in former croplands (sunflower and cereal fields) sown with a low-diversity seed mixture (composed of 2 native grass species) in Egyek-Pusztakócs, Hortobágy National Park, East-Hungary. The percentage cover of vascular plants was recorded in 4 permanent plots per field on 7 restored fields between 2006 and 2009. Ten aboveground biomass samples per field were also collected in June in each year. We addressed two questions: (i) How do seed sowing and annual mowing affect the species richness, biomass and cover of weeds? (ii) How fast does the cover of sown grasses develop after seed sowing? Weedy species were characteristic in the first year after sowing. In the second and third year their cover and species richness decreased. From the second year onwards the cover of perennial grasses increased. Spontaneously immigrating species characteristic to the reference grasslands were also detected with low cover scores. Short-lived weeds were suppressed as their cover and biomass significantly decreased during the study. The amount of litter and sown grass biomass increased progressively. However, perennial weed cover, especially the cover of Cirsium arvense increased substantially. Our results suggest that grassland vegetation can be recovered by sowing low diversity mixtures followed up by yearly mowing. Suppression of perennial weed cover needs more frequent mowing (multiple times a year) or grazing.

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