Assessing the microbial communities inhabiting drinking water networks and nitrifying enrichments with special respect on nitrifying microorganisms

This study provides a comprehensive microbiological survey of three drinking water networks applying different water treatment processes. Variability of microbial communities was assessed by cultivation-based [nitrifying, denitrifying most probable number (MPN) heterotrophic plate count] and sequence-aided terminal restriction fragment length polymorphism (T-RFLP) analysis. The effect of microbial community composition on nitrifying MPN values was revealed. The non-treated well water samples showed remarkable differences to their corresponding distribution systems regarding low plate count, nitrifying MPN, and the composition of microbial communities, which increased and changed, respectively, in distribution systems. Environmental factors, such as pH, total inorganic nitrogen content (ammonium and nitrite concentration), and chlorine dioxide treatment had effect on microbial community compositions. The revealed heterogeneous nitrifying population achieved remarkable nitrification, which occurred at low ammonium concentration (14–51 μM) and slightly alkaline pH 7.7–7.9 in chlorine dioxide disinfected water networks. No change was observed in nitrification-generated nitrate concentration, although nitrate-reducing (and denitrifying) bacteria were present with low MPN and characterized by sequence-aided T-RFLP. The community structures of water samples partially changed in nitrifying enrichments and had influence on the generated nitrifying, especially nitrite-oxidizing MPN regarding the facilitated growth of nitrate-reducing bacteria and even methanogenic archaea beside ammonia-oxidizing microorganisms and nitrite-oxidizing bacteria

Isolation and characterization of yeast strains from Badacsony, Hungary

In modern winery, starter strains are used for wine making to avoid the risk of slow or incomplete fermentation.However, application of commercial starter yeasts sometimes leads to a uniform character of the wines. On the other hand, indigenous (“terroir”) strains are adapted better to local conditions highlighting the specific taste of wine. In this study, we isolated local yeast strains from Badacsony wine region of Hungary and investigated with microbiological and molecular biological tests in order to develop indigenous starter selection method. As many as 480 yeast strains were isolated and grouped using carbohydrate and nitrogen sources. Finally, 80 selected isolates were characterized for important oenological features, including tolerance of glucose, ethanol and acetic acid. Fermentation ability, killer toxin, hydrogen sulfide and acid production of 80 selected isolates were also tested. Isolates were studied by applying two molecular methods based on rRNA gene sequencing and analysis of Ty retrotransposon's delta elements in case of Saccharomyces strains. Our results have shown that the isolated strains belong to 15 yeast species of 8 genera, and the diversity of yeast population was significantly high in the investigated vineyard. We have found that selection for technological properties was a potential way to find suitable strains from the local microbiome, because a high proportion of isolated wild yeast strains show beneficial oenological properties for wine making. Further, we studied 35 available starter yeasts to avoid re-isolation and we identified only 3 starter yeasts from grape and must samples, which can be considered as very low incidenc

Isolation and characterization of yeast strains from Badacsony, Hungary

461-473In modern winery, starter strains are used for wine making to avoid the risk of slow or incomplete fermentation. However, application of commercial starter yeasts sometimes leads to a uniform character of the wines. On the other hand, indigenous (“terroir”) strains are adapted better to local conditions highlighting the specific taste of wine. In this study, we isolated local yeast strains from Badacsony wine region of Hungary and investigated with microbiological and molecular biological tests in order to develop indigenous starter selection method. As many as 480 yeast strains were isolated and grouped using carbohydrate and nitrogen sources. Finally, 80 selected isolates were characterized for important oenological features, including tolerance of glucose, ethanol and acetic acid. Fermentation ability, killer toxin, hydrogen sulfide and acid production of 80 selected isolates were also tested. Isolates were studied by applying two molecular methods based on rRNA gene sequencing and analysis of Ty retrotransposon's delta elements in case of Saccharomyces strains. Our results have shown that the isolated strains belong to 15 yeast species of 8 genera, and the diversity of yeast population was significantly high in the investigated vineyard. We have found that selection for technological properties was a potential way to find suitable strains from the local microbiome, because a high proportion of isolated wild yeast strains show beneficial oenological properties for wine making. Further, we studied 35 available starter yeasts to avoid re-isolation and we identified only 3 starter yeasts from grape and must samples, which can be considered as very low incidence

Creation of a Paenibacil lus larvae culture collection from the causative agent of American foulbrood of honey bees (Apis mellifera)

SUMMARY Background: American foulbrood caused by P. larvae has great economic impact among the bacterial honey bee diseases. The causative agent and the notifiable disease occur worldwide, also in Hungary. P. larvae is a Gram-posi tive spore-forming bacterium species. The resistance of its spore is very high, accordingly it can survive for decades. American foulbrood is a disease of the bee brood and the infection may spread fast in the colony and between colo nies. Currently there is no effective treatment of the disease. Prevention from the clinical form of the disease might be aimed by the reduction of the number of spores in the bee hive. Using antibiotic treatment for honey bee colonies is forbidden in Hungary. The colonies showing clinical signs have to be killed, and the apiary gets quarantined. Objectives: Our purpose was to create a representative bacterial culture col lection of P. larvae in Hungary, in order to study the features of the Hungarian isolates (e.g. phenotypic and genotypic characters, susceptibility against disin fectants and so on). Materials and Methods: A total of 297 honey samples were collected from different parts of Hungary (19 counties, 143 settlements), and different cultural methods were used for the isolation of the causative agent. Based on the cul tural, morphological and biochemical features 82 isolates were cultured and stored in freezer at −80 °C till use. Identification of the isolates on species level was carried out using MALDI-TOF mass spectrometry, which identified all iso lates as P. larvae. Results and Discussion: As a result of our work on the one part the partici pating apiaries gained information about the infection of their colonies with the causative agent of American foulbrood, and on the other part a representative bacterial culture collection was set up, which comprise 82 P. larvae isolates from different parts of Hungary (17 counties, 49 settlements). This bacterial culture collection serves a basis for further research

Characterisation of in vitro antibacterial effect of a veterinary medical product called NAF against the caus ative agent (Paenibacillus larvae) of American foul brood of honey bee (Apis mellifera)

SUMMARY Background: American foulbrood (AFB) is the most important bacterial dis ease of honeybees with worldwide distribution, which causes high economic losses. The causative agent is P. larvae a Gram-positive, rod-shaped, motile, spore forming bacterium species. Usage of antibiotics for treatment of this dis ease is not allowed in most countries because of the residues in honey and other bee-products. Therefore, there is a great interest to find alternative and effective AFB-controlling natural substances, such as plant essential oils, which have natural antibacterial effect. Objectives: Antibacterial activity (Minimal Inhibitory Concentration) of a veteri nary medical product called „NAF” (Chemor Ltd., Hungary) against 30 P. larvae strains isolated from different area of Hungary was determined. Strains originat ing from Hungarian apiaries were isolated and identified in 2015. Materials and Methods: Vegetative cells of P. larvae were grown on Columbia Agar supplemented with 10% defibrinated sheep blood. Bacterial suspension was set to MacFarland standard 0.5 that corresponds with 105 CFU/ml bacterial density. Determination of MIC-values were carried out using broth dilution method in 48-well tissue culture plates. After the inoculation of the bacteria the tissue cul ture plates were incubated at 37 ºC for 48 hours. After the incubation period the bacterial growth was evaluated with naked eye. Results and Discussion: MIC range of NAF veterinary medical product was between 0.015 and 1.953 µl/ml in case of the investigated P. larvae strains. MIC50 and MIC90 values were both determined as 0.997 µl/ml. In vivo effect of the product should be carefully evaluated due to the poor infor mation about the concentration of the active ingredients in the royal jelly. There fore, conclusion about in vivo efficacy of the product should not be deducted, based on the in vitro susceptibility of the vegetative from of the pathogen

Characterization of Saccharomyces Strains Isolated from “Kéknyelű” Grape Must and Their Potential for Wine Production

Novel wine yeast strains have the potential to satisfy customer demand for new sensorial experiences and to ensure that wine producers have strains that can produce wine as efficiently as possible. In this respect, hybrid yeast strains have recently been the subject of intense research, as they are able to combine the favourable characteristics of both parental strains. In this study, two Saccharomyces “Kéknyelű” grape juice isolates were identified by species-specific PCR and PCR-RFLP methods and investigated with respect to their wine fermentation potential. Physiological characterization of the isolated strains was performed and included assessment of ethanol, sulphur dioxide, temperature and glucose (osmotic stress) tolerance, killer-toxin production, glucose fermentation ability at 16 °C and 24 °C, and laboratory-scale fermentation using sterile “Kéknyelű” must. Volatile components of the final product were studied by gas chromatography (GC) and mass spectrometry (MS). One isolate was identified as a S. cerevisiae × S. kudriavzevii hybrid and the other was S. cerevisiae. Both strains were characterized by high ethanol, sulphur dioxide and glucose tolerance, and the S. cerevisiae strain exhibited the killer phenotype. The hybrid isolate showed good glucose fermentation ability and achieved the lowest residual sugar content in wine. The ester production of the hybrid strain was high compared to the control S. cerevisiae starter strain, and this contributed to the fruity aroma of the wine. Both strains have good oenological characteristics, but only the hybrid yeast has the potential for use in wine fermentation.</p