Although fungicide resistance in crop pathogens is a global threat to food production, surprisingly little is known about the evolutionary processes associated with the emergence and spread of ...fungicide resistance. Early stages in the evolution of fungicide resistance were evaluated using the wheat pathogen Zymoseptoria tritici, taking advantage of an isolate collection spanning 20 years in Oregon, USA, and including two sites with differing intensity of fungicide use. Sequences of the mitochondrial cytb protein conferring single‐mutation resistance to QoI fungicides and the nuclear CYP51 gene implicated in multiple‐mutation resistance to azole fungicides were analysed. Mutations associated with resistance to both fungicides were absent in the 1992 isolates, but frequent in the 2012 collection, with higher frequencies of resistance alleles found at the field site with more intensive fungicide use. Results suggest that the QoI resistance evolved independently in several lineages, and resulted in significant mitochondrial genome bottlenecks. In contrast, the CYP51 gene showed signatures of diversifying selection and intragenic recombination among three phylogenetic clades. The findings support a recent emergence of resistance to the two fungicide classes in Oregon, facilitated by selection for mutations in the associated resistance genes.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In total, 230 single-conidial isolates of the fungal wheat pathogen Zymoseptoria tritici (formerly Septoria tritici, teleomorph: Mycosphaerella graminicola) were sampled in Morocco in 2008 and 2010 ...to assess resistance against quinone outside inhibitors (QoIs), a widely used group of fungicides in wheat pest management. All 134 isolates sampled in 2008 were QoI sensitive. In contrast, 9 of the 96 isolates from the 2010 collection were resistant, suggesting a recent emergence of the resistance. Mitochondrial (mt)DNA-sequence analyses identified four haplotypes among the resistant isolates. Wright's F statistics (F
) analyses from mtDNA sequences revealed a shallow population structure of Z. tritici within Morocco and a substantial asymmetric gene flow from Europe into Morocco. A phylogenetic reconstruction including Moroccan and European isolates clustered the haplotypes regardless of their geographic origin. The four Moroccan QoI-resistant mitochondrial haplotypes clustered in two distinct clades in the tree topology, suggesting at least two independent origins of the resistance. This study reported, for the first time, the occurrence of QoI-resistant genotypes of Z. tritici in Morocco. Our findings are consistent with the hypothesis that QoI resistance emerged very recently through parallel genetic adaptation in Morocco, although gene flow from Europe cannot be excluded.
Aims
The tyraminogenic potential of the strains Enterococcus faecalis EF37 and ATCC 29212 was investigated in a synthetic medium containing defined amounts of tyrosine and phenylalanine at different ...temperatures.
Methods and Results
Enterococci growth and the production of biogenic amines (BA) were evaluated in relation to their pre‐growth in medium containing tyrosine. Significant differences between the two strains were evidenced at metabolic level. Both the pre‐adapted strains grew faster in all the tested conditions, independently of the presence of the precursor. Temperatures of 30 and 40°C positively affected the growth parameters. The tyrosine decarboxylase (tyrDC) activity of the strain EF37 was positively affected by pre‐adaptation, while ATCC 29212 showed a faster and higher tyramine accumulation with not‐adapted cells. The expression analysis of the gene tyrDC confirmed the influence of the growth conditions on gene transcription.
Conclusions
The small differences found between the two strains in the maximum transcript level reached rapidly after the inoculum and the different behaviour in the tyramine accumulation suggested the possible involvement of complex regulation mechanisms on the tyrDC or on the membrane transport systems, which could affect the different BA accumulation trend.
Significance and Impact of the Study
This study gives deeper insight into the metabolic regulation of tyrDC activity of enterococci.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Aims
To investigate the Oenococcus oeni population occurring during spontaneous malolactic fermentation (MLF) of Amarone wine, a peculiar and hostile environment for malolactic bacteria.
Methods and ...Results
Pulsed‐field gel electrophoresis (PFGE) analysis showed a high level of genetic heterogeneity within the O. oeni population involved in MLF throughout an industrial vinification of Amarone wine. The 13 strains with distinct PFGE profile displayed different capability to hydrolyse esters and glycosides, as well as great variability to growth under stress parameters, such as high ethanol content (15% v/v), low pH (3·0) and temperature (15°C), and presence of SO2. Moreover, polymorphism in the gene sacB involved in exopolysaccharide production was observed among the strains. The strains showed differences to convert l‐malic acid into l‐lactic acid in wine.
Conclusions
The occurrence of spontaneous MLF in stressful ecosystems such as Amarone wine is related to the heterogeneity of O. oeni community; biodiversity indexes and strain evolution analyses suggested that its success depends on its initial strain evenness.
Significance and Impact of the Study
Remarkable intraspecies complexity within the O. oeni natural population could explain the great versatility of this species as key of successful adaptation to harsh winemaking conditions.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The microbiota of Serrano dry-cured ham of different chemical composition, subjected or not to high-pressure processing (HPP), was investigated using culture-dependent and culture-independent ...methods. Microbial counts were submitted to analysis of variance with physicochemical parameters (aw, NaCl concentration, salt-in-lean ratio and intramuscular fat content) or HPP as main effects. In untreated hams, physicochemical parameters significantly affected counts of aerobic mesophiles, psychrotrophs, and moulds and yeasts. NaCl concentration and fat content influenced the levels of four and three of the five studied microbial groups, respectively, whereas no influence of aw was stated. The HPP treatment had a significant effect on counts of all investigated microbial groups. Culture-independent methods showed the presence of bacteria such as Staphylococcus equorum, Staphylococcus succinus, Bacillus subtilis and Cellulosimicrobium sp., moulds like Penicillium commune, Aspergillus fumigatus, Sclerotinia sclerotiorum, Eurotium athecium and Moniliella mellis, and yeasts like Debaryomyces hansenii and Candida glucosophila. Absence of B. subtilis bands and weaker bands of E. athecium were recorded for HPP-treated hams.
The higher microbial levels found in lean ham might result in a quicker deterioration. HPP treatment confirmed its suitability as a procedure to control spoilage microorganisms. DGGE did not seem to be sensitive enough to highlight changes caused by HPP treatment in the microbiota of ham, but contributed to the detection of microbial species not previously found in ham.
•Microbiota of Serrano ham of different chemical composition was investigated.•Microbial counts were higher in hams of high salt content and low intramuscular fat.•Culture-independent methods contributed to the detection of microbial species not previously found in ham.•High-pressure-processing significantly lowered the counts of all microbial groups.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Diet-related modulation of gut microbiota and its metabolic activity represents an intriguing research context, particularly in the case of disorders related to imbalances in gut microbial ...communities. We here explored the effects of Bacillus coagulans GBI-30, 6086 (BC30), β-glucans, and innovative whole-grain pastas, with or without these functional ingredients, on gut microbiota from three groups of children, presenting different susceptibility to type 1 diabetes, by using the well-controlled TNO in vitro model of the proximal colon (TIM-2). Short- and branched-chain fatty acids production and microbiota composition were assessed by means of gas chromatography and 16S rRNA gene profiling, respectively. In most cases, in vitro dietary interventions caused microbiota-dependent modulations as a result of intergroup variability, but also specific changes in microbial groups were shared between the three microbiotas, highlighting specific diet-microbial taxa connections.
The present paper reports the first application of FTIR microspectroscopy in the mid-infrared range to study the major biochemical changes associated with autolysis in yeast cells. Measurements were ...done both in transmission and in attenuated total reflection (ATR) mode on cells of
Saccharomyces cerevisiae strain EC1118 before and after induction of the autolytic process in a model wine medium and in a
Chardonnay base wine. Unsupervised multivariate statistical analysis (Hierarchical Cluster Analysis and Principal Component Analysis), as well as accurate spectral analysis based on curve fitting, were applied to the acquired spectra. The spectral behaviour of
S. cerevisiae in the model and base wines was found to be the same. A detailed interpretation of absorption bands was given by reference to the literature and through comparison of transmission and ATR spectra. It was shown that FTIR microspectroscopy is a rapid and accurate tool to simultaneously probe the major biochemical events associated with the autolytic process. Moreover, the intrinsically higher sensitivity of ATR with respect to transmission spectra in analyzing autolysis was also demonstrated.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The aims of this work were to identify and characterize for some important technological properties the yeast species present throughout the ripening process of Pecorino Crotonese, a traditional ...cheese produced in a well defined area of Southern Italy. In particular, the strain technological properties considered include fermentation/assimilation of galactose and lactose, assimilation of lactate and citrate in the presence of different NaCl concentrations, hydrolysis of butter fat, skim milk, gelatine and casein, production of brown pigments in cheese agar and ability to produce biogenic amines. High yeast levels were recorded in cheese samples already after 5
h of brining (about 5
log
cfu/g) and these concentration remained constant during ripening. The yeast isolates belonged to restrict number of yeast species. While
Kluyveromyces lactis and
Saccharomyces cerevisiae were isolated prevalently in the first stages of Pecorino Crotonese production,
Yarrowia lipolytica and
Debaryomyces hansenii dominated during the later stages of maturation. Otherwise, the latter two were very NaCl resistant species. In fact,
D. hansenii strains conserved the ability to assimilate lactose and galactose in the presence of 10% NaCl, while almost all the strains of
Y. lipolytica isolated assimilated citrate and lactate up to 7.5% NaCl.
Y. lipolytica isolates evidenced also the highest proteolytic and lipolytic activities and the capability to catabolize tyrosine producing brown pigment. In addition they resulted in the highest aminobiogenic potential decarboxylating ornithine, phenylalanine, tyrosine and lysine. However, they were not able to produce histamine, biogenic amine produced by three strains of
D. hansenii.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The production of biogenic amines (BA) during the manufacturing and ripening of sheep milk Pecorino Abruzzese cheeses prepared from raw milk without starter culture (A) and from pasteurized milk with ...added starter (B) were compared. At the end of ripening (60 days), the total BA contents of cheeses of batches A and B were 697 and 1086
mg
kg
−1, respectively; the dominant BA were different. Single isolates of enterococci, pseudomonads and
Enterobacteriaceae were screened for their potential to produce BA. Qualitative tests indicated a large spread of BA-forming cultures among the members of the
Enterobacteriaceae and lactic acid bacteria (LAB). Differences among the levels of BA produced in UHT milk by representative isolates of coliforms,
Pseudomonas and LAB were observed in relation to the microbial group or the isolate. The results emphasize the need to improve the general hygienic conditions of Pecorino Abruzzese cheese manufacture and control the indigenous bacterial population.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
To evaluate the concomitant effects of three technological variables (fermentation temperature, NaCl and glucose added to the meat batter) on diamines (cadaverine, putrescine and histamine) ...accumulation and microbial changes during ripening of dry fermented sausages. The variables were modulated according to an experimental design and predictive mathematical models were obtained. The models indicated that the sausages were characterized by low histamine amount independently on the applied conditions. In contrast, putrescine and cadaverine accumulation was considerable and significantly affected by the three variables. The microbial population dynamics suggest that lactic acid bacteria (LAB) and microstaphylococci are favoured by increasing glucose concentration until 0·7 g kg⁻¹, while Enterobacteriaceae are negatively influenced by NaCl concentration and, to a lesser extent, by fermentation temperature. Data obtained showed a relationship between Enterobacteriaceae growth and cadaverine and putrescine accumulation in sausages during ripening. The conditions more favourable for LAB and microstaphylococci induced a reduced growth of Enterobacteriaceae with a consequent reduced accumulation of putrescine and cadaverine. The use of systematic experimental designs allows to individuate the technological conditions suitable to keep the aminogenic microflora under control, thus reducing the risk of diamines production during traditional fermented food manufacture.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
PDF
