Biology subjects

Leitner, G.

Publications and source records attributed to Leitner, G..

3 recordsLinked to original sources

bioRxiv2019

The physiological response in the mammary gland to Escherichia coli infection reflects a conflict between glucose need for milk production and immune response

Upon entry into the mammary gland, mammary pathogenic strains of Escherichia coli rapidly grow using milk as a nutrient source, in a manner highly dependent on the expression of the ferric-dicitrate system by these bacteria. Intra-mammary challenge with distinct mammary pathogenic E. coli (MPEC) strains result in development of clinical acute mastitis, with peak bacterial counts in milk at 16-24 h post-challenged and profound immune changes found in the milk. The main biochemical changes measured in milk were partially in accord with lipopolysaccharide-induced mastitis, with increased glucose-6-phosphate and lactate dehydrogenase activity or prolonged lactate dehydrogenase, and Glu6P/Glu alterations. Changes also reflect physiological responses to inflammation in the mammary gland, as in the balance between aerobic and anaerobic metabolism (citrate to lactate ratios). Some alterations measured in milk resolved with days after challenge but other remained for above one month, regardless of bacterial clearance. The results suggest that E. coli mastitits can be divided into two stages: an acute, clinical phase, as an immediate response to bacterial infection in the mammary gland and a chronic phase, independent of bacteria clearance, and in response to the tissue damage caused in the first phase.

physiology↗

bioRxiv2019

Increasing the value of raw bulk milk quality based on mammary glands as production units vs. the udder in dairy cows with mastitis

The current study measured the influence of milk of subclinically infected glands by different bacteria species on the cows milk and suggests different parameters for milk payment. The effects of bacterial infection or inflammation on gland milk yield were related to the bacteria species that caused the infection. The volume of milk of the inflamed gland from the cows milk yield was significantly lower (P<0.001) for the glands previously infected by Escherichia coli (PIEc) and those infected with Streptococcus dysgalactiae. Coagulation properties, rennet clotting time (RCT) and curd firmness (CF) also depended on the bacteria causing the infection. RCT values of all the inflamed glands were significantly longer (P<0.001) and CF values were significantly lower than that of the healthy ones. Moreover, in the whole milk, CF was also significantly lower and not proportional to the volume of the milk from the inflamed gland of the cows milk. Calculating the predicted 40% dry matter curd weight (PCW) on the cow level, including the healthy and inflamed glands or the healthy glands alone, found that for 9 of 13 PIEc cows, the presence of the affected glands milk in the whole cow milk resulted in a negative PCW value. Likewise, 5 of 20 cows infected by S. dysgalactiae had negative delta values. Unlike the latter bacteria, PCW from milk of glands infected with CNS increased, although in a lower magnitude than in the healthy glands. No correlation was found between logSCC in the whole cow milk (healthy and inflamed glands) and PCW.

systems biology↗

bioRxiv2018

Fermentation characteristics of mead and wine generated by yeasts isolated from beehives of two Austrian regions

Mead is a traditional alcoholic beverage that is produced by fermentation of diluted honey. The mead quality is primarily influenced by the honey variety, although the yeast microflora as the main catalyst of alcoholic fermentation also plays a significant role in the organoleptic and chemical quality of the final product. The impact of the indigenous honey associated-yeasts on the mead properties has scarcely been investigated. To fill this gap the main objective of this work was to assess the metabolic properties of the yeasts isolated from honey and pollen from beehives of northeast Austria.\n\nThe biodiversity was low and only two yeast species were identified, Zygosaccharomyces rouxii and Candida apicola. The fermentation potentials of these yeasts were estimated in two media, grape juice (since yeasts isolated from honey may be useful for sweet wine production) and diluted honey of similar sugar concentration, and compared with those of the reference strains Saccharomyces cerevisiae; S. uvarum and S. eubayanus. Depending on the fermentation substrate, yeasts differed with respect to their metabolic power, fermentation rate, sugar utilization and production of glycerol and organic acids. During mead fermentation Saccharomyces species showed the highest metabolic turnover, while the fermentation rate did not differ significantly. Addition of assimilable nitrogen to the diluted honey enhanced fermentation rate of S. cerevisiae, but not of the other species. Fermentation of grape juice occurred much faster than that of diluted honey and differences between yeasts were more pronounced. The S. cerevisiae commercial wine strain, adapted to high alcohol concentrations, and S. eubayanus outperformed the others, S. uvarum was comparable with Z. rouxii, while C. apicola had the lowest fermentation rate. Fructophily of Z. rouxii and to a lesser degree of C. apicola was observed in both media. An increased production of glycerol was achieved by S. eubayanus in both media and by C. apicola during the fermentation of honey must. A commercial S. cerevisiae strain, S. eubayanus and Z. rouxii were able to metabolize malic acid in wine. In mead, the S. eubayanus and S. uvarum yeasts showed the tendency of increasing the level of malic acid. Aroma profile depended profoundly on yeast species. This study demonstrates that the composition and complexity of the fermentation substrate determines the activity and the final metabolic outcomes of the studied yeasts.

microbiology↗