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“Talaj – növény holobiont komplex – a megismeréstől az alkalmazásig”•

tudományos előadóülés (on-line), 2021. szeptember 16.

Agrokémia és Talajtan
Authors: Szili-Kovács Tibor and Márialigeti Károly
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In this study, changes in the bacterial community composition of the well waters of Harkány Spa were examined. Physical and chemical properties of mixing subsurface cold and thermal karst waters were correlated to shifts in bacterial community structures analyzed by denaturing gradient gel electrophoresis (DGGE) and principal component analysis (PCA). In addition, mineral components of the pellets were investigated by scanning electron microscopy. Samples from the effluent waters of Büdöstapolca I and II, Matty and Thermal VI wells were taken seasonally in 2007 and 2008. The comparison of the results of DGGE and PCA analyses showed that bacterial communities from the Büdöstapolca wells were distinct from those of Matty and Thermal VI, but seasonal changes were not detected. According to the phylogenetic analysis of the excised DGGE bands, presence of chemolithotrophic Proteobacteria (Thiobacillus, Thiothrix, and distant relatives of Sulfurospirillum) were typical in the Büdöstapolca wells, while members of Actinobacteria (Plantibacter, Actinobacterium, Microbacterium) and Firmicutes (Planococcus) were characteristic to the Matty and Thermal VI wells. In the pellets pyrite framboid crystals were observed by electron microscopy, which are minerals known to be biologically induced by dissimilatory iron- and sulfur (sulfate)-reducing bacteria.

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Because of the selectivity of the commonly used media it is very difficult to cultivate bacteria inhabiting ultrapure waters under laboratory conditions. In this study 5 new media (synthetic and complex) were developed to reveal bacterial community of the ultrapure water originated from the water purification system of a Hungarian power plant which was studied already with using traditional media. Composition of the new media tends to reproduce the nutrient deficient conditions of the investigated water, therefore media were highly oligotrophic. Altogether 122 bacterial strains were isolated from the 5 different media. Based on ARDRA grouping 27 strains were chosen for the partial 16S rRNA gene sequence analysis. The results showed that the applied media strongly influence the composition of the cultivable bacterial community. A larger scale of α-Proteobacteria (Mesorhizobium spp., Ancylobacter sp., Methylobacterium sp.) and many Actinobacteria (Leifsonia sp., Microbacterium spp., Mycobacterium spp.) could be isolated from the same ultrapure water system than with any other cultivation methods or media applied before. Moreover, two novel bacterial taxa could be isolated from the studied water purification system.

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Lake Hévíz is a unique thermal spa located in Hungary. Owing to the thermal springs nourishing the lake, it has a relatively rapid water turnover. In spring 2011 a comprehensive embankment reconstruction was performed to preserve the water supply of the surrounding wetland habitats. The physical and chemical parameters as well as the planktonic microbial communities were studied with special respect to the effect of the disturbance of the water of Lake Hévíz. According to the abiotic components, both temporal and spatial differences were revealed with the exception of autumn samples. The reconstruction resulted in a short term but dramatic alteration of the total planktonic bacterial and cyanobacterial community structures as revealed by denaturing gradient gel electrophoresis. In addition, greater seasonal than spatial differences of bacterial communities were also observed. Planktonic bacterial community composition of Lake Hévíz included mainly typical freshwater species within phylum Actinobacteria, Chloroflexi, Cyanobacteria and class Alpha-, Beta- and Gamma-proteobacteria. Most of them were aerobic or facultative anaerobic heterotrophic but chemolitotrophic (e.g. Thiobacillus) or photolithotrophic (e.g. Cyanobacteria and Chloroflexi) autotrophic microbes were also identified.

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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.

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Lake Hévíz is the largest natural warm water lake of Europe. The curative mud of the lake comprises volcanic and marsh components although their species composition is hardly known yet. The aim of the present study was to gain information about the distribution and species diversity of bacterial communities inhabiting the sediment of Lake Hévíz using cultivation-based and molecular cloning methods. Samples from two depths and locations were taken in 2004 and 2007. Representatives of the altogether 255 bacterial isolates were affiliated with the phyla Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes. The most abundant groups belonged to the genus Bacillus (Firmicutes). Many of Lake Hévíz isolates showed the highest sequence similarity to bacteria known to be plant associated or members of normal human microbiota as well as participating in decomposition of highly resistant organic materials. In the three clone libraries, phylotypes belonging to altogether different phyla (Firmicutes, Actinobacteria, Proteobacteria, Bacteroidetes, Cyanobacteria, Chlorobi, Chloroflexi, Deferribacteres, Nitrospirae, Spirochaetes and Verrucomicrobia) were revealed from which members of Gammaproteobacteria and Cyanobacteria proved to be the most abundant. Regardless of the sampling times and methodology used, high spatial heterogeneities of bacterial community structures were characteristic of the sediment of Lake Hévíz.

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Agrokémia és Talajtan
Authors: Gergely Ujvári, Andrea Borsodi, Júlia Margit Aszalós, Melinda Megyes, Márton Mucsi, Attila Szabó, and Károly Márialigeti

E tanulmány célja egy martonvásári hosszútávú tartamkísérlet trágyázás nélkül művelt kukorica monokultúra talajában fellelhető baktériumközösségek filogenetikai diverzitásának és anyagcsere potenciáljának a felmérése volt. A kutatás során NGS és MicroResp™ technikával vizsgáltuk a művelt és a természeteshez közeli állapotú talajok mikrobiális jellemzőit.

Az NGS adatai alapján a kukorica monokultúra szántott rétegének mintáinak baktériumközösség szerkezete nagyfokú hasonlóságot mutatott egymással, és elkülönült a löszpusztagyep A és C rétegéből formálódó csoporttól, míg a kukorica monokultúra C szintjéből származó minta élesen elvált a többitől. A gyepek talajában nem találtunk nagyobb bakteriális taxonómiai diverzitást, mint a művelt talajokban.

A MicroResp™ mérés alapján megállapítottuk, hogy a természeteshez közeli állapotú talajok felszínhez közeli (A) rétegében kiugró a mikrobiális aktivitás mértéke. A kukorica monokultúrából származó A szint minták mikrobiális aktivitási mintázata egymáshoz hasonló volt, a C rétegből származó minták külön csoportot képeztek.

Eredményeink alapján tehát a hosszú távú tartamkísérletbe vont művelt talajok baktériumközösségeinek filogenetikai diverzitása és metabolikus potenciálja jelentősen eltért a löszpusztagyep mintákétól.

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Acta Microbiologica et Immunologica Hungarica
Authors: Sára Szuróczki, Zsuzsa Kéki, Szandra Káli, Anett Lippai, Károly Márialigeti, and Erika Tóth

Thermal baths are unique aquatic environments combining a wide variety of natural and anthropogenic ecological factors, which also appear in their microbiological state. There is limited information on the microbiology of thermal baths in their complexity, tracking community shifts from the thermal wells to the pools. In the present study, the natural microbial community of well and pool waters in Gellért bath was studied in detail by cultivation-based techniques. To isolate bacteria, 10% R2A and minimal synthetic media (with “bath water”) with agar–agar and gellan gum were used after prolonged incubation time; moreover, polyurethane blocks covered with media were also applied. Strains were identified by sequencing their 16S rRNA gene after grouping them by amplified rDNA restriction analysis. From each sample, the dominance of Alphaproteobacteria was characteristic though their diversity differed among samples. Members of Actinobacteria, Firmicutes, Beta- and Gamma-proteobacteria, Deinococcus–Thermus, and Bacteroidetes were also identified. Representatives of Deinococcus–Thermus phylum appeared only in the pool water. The largest groups in the pool water belonged to the Tistrella and Chelatococcus genera. The most dominant member in the well water was a new taxon, its similarity to Hartmannibacter diazotrophicus as closest relative was 93.93%.

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Acta Microbiologica et Immunologica Hungarica
Authors: Mónika Knáb, Tibor Szili-Kovács, Károly Márialigeti, János Móga, and Andrea K. Borsodi

Karst areas have great environmental importance as sources of subsurface water and often maintain very sensitive ecosystems. In recent years, increasing number of microbiological studies focused on the bacterial communities of karst soils. In this study, diversity examinations on two distinct Hungarian karst areas, Aggtelek and Tapolca, were performed using parallel cultivation and molecular cloning methods. The phylogenetic affiliation of bacterial strains and molecular clones was determined based on their 16S rRNA gene sequences. Bacterial isolates were identified as members of the phyla Actinobacteria, Firmicutes, Proteobacteria, and Bacteroidetes. Besides the taxa identified by cultivation, members of the phyla Chloroflexi, Cyanobacteria, Acidobacteria, Verrucomicrobia, and Gemmatimonadetes were detected by the cloning. The difference in the composition of soil bacterial communities was related to geographic locations and soil types. Both the highest and the lowest bacterial diversities were detected in samples from Aggtelek National Park, characterized by Leptic Luvisol and Rendzic Leptosol soil types. The difference in the composition of bacterial communities between Rendzic Leptosol and Leptic Phaeozem soil types at Tapolca could be the result of human impacts.

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A preliminary study was conducted to compare the community level physiological profile (CLPP) and genetic diversity of rhizosphere microbial communities of four plant species growing nearby Kiskunság soda ponds, namely Böddi-szék, Kelemen-szék and Zab-szék. CLPP was assessed by MicroResp method using 15 different substrates while Denaturing Gradient Gel Electrophoresis (DGGE) was used to analyse genetic diversity of bacterial communities. The soil physical and chemical properties were quite different at the three sampling sites. Multivariate statistics (PCA and UPGMA) revealed that Zab-szék samples could be separated according to their genetic profile from the two others which might be attributed to the geographical location and perhaps the differences in soil physical properties. Böddi-szék samples could be separated from the two others considering the metabolic activity which could be explained by their high salt and low humus contents. The number of bands in DGGE gels was related to the metabolic activity, and positively correlated with soil humus content, but negatively with soil salt content. The main finding was that geographical location, soil physical and chemical properties and the type of vegetation were all important factors influencing the metabolic activity and genetic diversity of rhizosphere microbial communities.

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