Comparison of phytoplankton of 80s and late 90s in a large side arm of the Danube River (Soroksár-Danube/Hungary)

The chlorophyll-a content, abundance and taxonomic composition of phytoplankton were studied in the Soroksár-Danube between 1984-87 and 1999. Samples were taken biweekly in the 80’s, monthly in 1999 at Dunaharaszti (the upper part of the side arm) and at Ráckeve (the lower part of the side arm) and from the main arm of the Danube River to compare the qualitative and quantitative composition of phytoplankton. The potential trophic state of Soroksár-Danube is hypertrophic, the actual trophic level is meso-, eutrophic in winter and eu- hypertrophic in other seasons. When the annual water discharge was low, the phytoplankton abundance became higher int he Soroksár Danube compared to the main arm, caused by a high abundance of centric diatoms. When the annual water discharge was high, the abundance of phytoplankton was similar to the main arm. In the other cases, the abundance of phytoplankton of the upper part of the Soroksár-Danube was similar to the main arm, but that of the lower part was different from it (two-three times higher). The much abundant phytoplankton of the side arm flowing back to the main arm can increase the trophic level of the river

Silver- and sulfadiazine-loaded nanostructured silica materials as potential replacement of silver sulfadiazine

Silver sulfadiazine (AgSD) is the leading topical antibacterial agent for the treatment of burn wound infections. Antibacterial effect of AgSD is limited by its poor aqueous solubility, and antibacterial activity develops only by decomposition of AgSD to silver ions and sulfadiazine. In this study, it is for the first time that application of silver-modified nanoporous silica carriers (MCM-41 or SBA-15) loaded with sulfadiazine (SD), instead of silver sulfadiazine, overcoming the abovementioned disadvantages has been demonstrated. By direct or post synthesis methods, 5–15 nm sized silver nanoparticles can be stabilized in the channels or on the outer surface of nanoporous silica supports; moreover, the empty channels can be loaded by SD molecules. The SD-loaded, silver-modified materials show sustained release properties and similar or even better antimicrobial properties than AgSD. Adsorption of AgSD on nanoporous silica particles significantly improves its water solubility

Critical point analysis and biocide treatment in a microbiologically contaminated water purification system of a power plant

Many industries use ultrapure water (UPW) for their operation. In spite of purification efforts, microbial contaminations are the major cause of manufacturing problems in these systems. In our experiments, the water purification system of a power plant was investigated: the microbiologically critical points of the ultrapure water purification system were located by checking the number and diversity of bacteria to determine the optimum operational unit for chemical intervention: the most contaminated site was the mixed-bed ion-exchange resin containing unit. Biocides were tested against bacteria previously isolated from the same system; effect of biocides was checked also in laboratory model systems, and based on the results, a biocide treatment was carried out in the mixed-bed ion-exchange resin columns of the working power plant. Kathon WT was the most effective from the studied chemicals, being effective already in low concentration against most studied microorganisms. In case of the handling of the mixed-bed ion-exchange resin, 8-h treatment with 25ppm biocide concentration was effective. Following the treatment, the quality of the produced UPW met the standards (specific electric conductivity was<1.0x10(-3)mu Scm(-1) at 25 degrees C) and water production capacity increased; moreover, the run-down time of the mixed-bed ion-exchange resin significantly grew

Short-term colonization sequence of periphyton on glass slides in a large river (River Danube, near Budapest)

The colonization, structure and composition of the periphyton which developed on the artificial substratum (sand-blasted matglass-slides) positioned into current line were studied in the main arm of the River Danube at Göd (1669 riv. km) in the summer of 1997, during a low water period. Five replicates were taken on the first day in the 3rd, 6th, 9th and 24th hour, after that every day for a week, then every three days for another two weeks. Phytoplankton samples were taken four times during the study (on the 1st, 6th, 13th and 20th day) to compare the composition of benthic and planktic algae. Altogether 222 taxa were identified 95 taxa from the phytoplankton and 176 from the periphyton. The number of common species was 50. after three hours from the immersion, only coccoid bacteria (mainly colineforms) were found on the substratum but after 6 hours the first algae. The first colonizer was Diatoma vulgaris, which adheres with on apical pad. In the first few hours only a few species formed the community and low diversity and low evenness was the consequence. After 24 hours the community was already diverse with a total of 35 species. During the first week of colonization the periphyton was composed almost exclusively of quick reproduction rate R (ruderal strategy) selected species, the evenness showed an increase parallel to species richness. The basal-layer of the Danube periphyton developed at that time, where diatoms attached to the substratum mainly with on apical pad. From the second week there was a small decrease in the evenness, when the rate of slower multiplying C, C-S (competitive strategy, stress tolerant strategy) selected species increased. In the second week stalk forming species formed an intermediate layer adhering with long, branching gelatinous stalk. The thick periphyton cover filtered out planktic species from the water like a net, and more and more euplanktic Centrales species were found in the samples

Biofilm forming bacteria and archaea in thermal karst springs of Gellért Hill discharge area (Hungary)

The Buda Thermal Karst System (BTKS) is an extensive active hypogenic cave system located beneath the residential area of the Hungarian capital. At the river Danube, several thermal springs discharge forming spring caves. To reveal and compare the morphological structure and prokaryotic diversity of reddish-brown biofilms developed on the carbonate rock surfaces of the springs, scanning electron microscopy (SEM), and molecular cloning were applied. Microbial networks formed by filamentous bacteria and other cells with mineral crystals embedded in extracellular polymeric substances were observed in the SEM images. Biofilms were dominated by prokaryotes belonging to phyla Proteobacteria, Chloroflexi and Nitrospirae (Bacteria) and Thaumarchaeota (Archaea) but their abundance showed differences according to the type of the host rock, geographic distance, and different water exchange. In addition, representatives of phyla Acidobacteria, Actinobacteria, Caldithrix, Cyanobacteria, Firmicutes Gemmatimonadetes, and several candidate divisions of Bacteria as well as Crenarchaeota and Euryarchaeota were detected in sample-dependent higher abundance. The results indicate that thermophilic, anaerobic sulfur-, sulfate-, nitrate-, and iron(III)-reducing chemoorganotrophic as well as sulfur-, ammonia-, and nitrite-oxidizing chemolithotrophic prokaryotes can interact in the studied biofilms adapted to the unique and extreme circumstances (e.g., aphotic and nearly anoxic conditions, oligotrophy, and radionuclide accumulation) in the thermal karst springs

Bacterial and abiogenic carbonates formed in caves–no vital effect on clumped isotope compositions

Speleothems (dominated by cave-hosted carbonate deposits) are valuable archives of paleoclimate conditions. As such, they are potential targets of clumped isotope analyses that may yield quantified data about past temperature variations. Clumped isotope analyses of stalagmites, however, seldom provide useful temperature values due to various isotope fractionation processes. This study focuses on the determination of the microbially induced vital effect, i.e., the isotope fractionation processes related to bacterial carbonate production. A cave site with biologically mediated amorphous calcium carbonate precitation was selected as a natural laboratory. Calcite deposits were farmed under a UV lamp to prevent bacterial activity, as well as under control conditions. Microbiological analyses and morphological investigations using scanning electron microscopy showed that the UV lamp treatment effectively reduced the number of bacterial cells, and that bacterial carbonate production strongly influenced the carbonate's morphology. Stable oxygen isotope analyses of calcite and drip waters, as well as clumped isotope measurements revealed that, although most of the studied carbonates formed close to oxygen isotope equilibrium, clumped isotope Δ47 values varied widely from equilibrium to strongly fractionated data. Site-specific kinetic fractionations played a dominant role in the distribution of Δ47 values, whereas bacterial carbonate production did not result in a detectable clumped isotope effect