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Metabolic activity of heterotrophic bacteria isolated from coastal lake Łebsko was determined using the respirometric method. It has been shown that planktonie bacteria oxidized organic compounds with various intensity. Caseine hydrolyzate was the most intensively oxidized respiratory substrate, whereas cellobiose was oxidized the least intensively. In the studied lake, oxygen was taken up most actively by bacteria of the Flavobacterium-Cytophaga group and the genus Pseudomonas in their respiratory processes. The level of metabolic activity of bacteria from different parts of the lake was shown to differ. The oxygen uptake of bacterial mixtures was, as a rule, lower than the sum of oxygen uptake of single strains.
Studies were carried out on the utilization of various carbohydrates by planktonie bacteria isolated from the estuarine lakes Łebsko, Gardno and Jamno. The most actively utilized carbohydrates were glucose, fructose, lactose and saccharose; the least active was rhamnose. Pronounced seasonal variability in the utilization of carbohydrates was found. However, no significant differences were found at the particular research stations.
The investigation was conducted in the Kopački Rit Nature Park (eastern Croatia) which is established to protect the floodplain area of the Danube River. The samples were collected monthly in four sites (channels and lakes) with increasing distance from the river. The aim of investigation was to examine trophic structure of culturable bacterioplankton in relation to inundation-isolation cycles on sampling sites with unequal degree of connection with the Danube river. A change in the ratio of copiotrophs (r-strategists) to oligotrophs (K-strategists) was expected as the different organic carbon sources emerged. The composition of variables was revealed by Principal Component Analysis of abiotic water properties (temperature, water depth, transparency, pH, electrical conductivity, dissolved oxygen, nutrient concentrations) and the chlorophyll-a concentration. Scores of significant components were used in a Multiple Regression as independent variables and the relationship between the scores and abundance of colony forming units (CFUs) was examined. Regression model was significant only for copiotrophs, and their relative dominance was noticed in couple of samples on more isolated sampling sites. In all other samples oligotrophs were a dominant group, especially during the flood pulses or drainage after it. Their elevated abundance was equally distributed in all groups revealed by Principal Component Analysis, and corresponds to the fluvial action. Also concerning the η (eta) squared and R squared values from the two-way ANOVA (sites/samplings) oligotrophs are highly influenced by the sampling period i.e. inundation-isolation cycles. They are probably driven by the allochthonous organic matter provided by floods or have allochthonous origin itself. At the same time, copiotrophs are to some extent coupled with the established water properties, i. e. bottom-up controlled and their abundance is influenced by the localisation of sampling sites in the floodplain. These results describe the development of the conditions that promote habitat specific succession of the culturable bacterioplankton. Established differences had disappeared after additional inundation-isolation cycles.
The paper presents the results of the study of abundance and secondary production of neustonic and planktonic bacteria inhabiting estuarine Lake Gardno. The obtained data indicate that numbers of bacterioneuston were only slightly higher than of bacterioplankton. The rate of secondary production of bacteria was higher in the film layer than in the surface layer and subsurface water. Bacterial abundance and production were changing with seasons. Differences among studied bacteriological parameters were determined among sites across Lake Gardno.
The study was carried out in the estuarine part of the Słupia River, which, for the most part, comprises the harbour channel. The results of the present study showed that the total abundance of bacterioneuston was higher compared to bacterioplankton. In these two groups of bacteria, dead bacterial cells were dominant. The total number of bacteria, as well as the number of live and dead bacteria was similar in the entire horizontal profile. The abundance of live and dead bacteria showed distinct seasonal variation.
The object of study was the effect of metal ions Hg+2, Cu+2, Zn+2 on the development of neustonic and planktonie bacteria from Lake Jeziorak Maly. It was found that planktonie bacteria were moře susceptible to the heavy metal ions used in the experiment than neustonic bacteria. The bacteria showed higher tolerance to various concentrations of heavy metals in spring and summer than in autumn and winter. Neustonic bacteria isolated from sites exposed to municipal and industrial pollution showed higher tolerance to increased concentrations of heavy metals. Bacteria cultured in trophically rich medium were less susceptible to various concentrations of heavy metals than those cultured in trophically poor medium. The effect of toxicity of heavy metal ions on bacteria increased with the increase in their concentration and decreased in the following succession: Hg>Cu>Zn.
Neustonic (film layer ~ 90 µm, surface layer ~ 240 µm) and planktonic bacteria (subsurface layer ~ 10–15 cm) participating in the processes of decomposition of organic macromolecular compounds, and their potential capability to synthesise extracellular enzymes were studied in a shallow estuarine lake (Lake Gardno – Baltic coast). The studied bacteria were capable of decomposing a wide spectrum of organic macromolecular compounds. Most bacteria inhabiting surface and subsurface water layers hydrolysed lipids, proteins and DNA. The microflora hydrolysing cellulose was represented by the least abundant group of organisms. Of the studied enzymes, alkaline and acid phosphatases, leucine arylaminase, esterase, and esterase lipase were synthesised most actively while β-glucouronidase (βGl) and α-fucosidase (αFu) were synthesized least actively. It can be clearly seen that enzymatic activity was stratified, and there were differences between studied water layers. Bacterial strains isolated from surface and subsurface layers were more active in synthesizing extracellular enzymes than bacteria inhabiting the film layer. Bacteria isolated from various parts of Lake Gardno synthesized the tested hydrolytic enzymes with a similar intensity.
The effect of two different reservoirs on some parameters of river water quality has been studied. The Antoninek Reservoir (wetland-type, mean depth 0.4 m, area 7.2 ha, mean residence time 0.5 day) and the Maltański Reservoir (also not stratified but plankton-type, mean depth 3.1 m, area 64 ha, mean residence time 34 days) are situated on the same river (mean discharge 0.67 m³ s⁻¹). Water of this river, which leaves the hypertrophic Swarzędzkie Lake upstream from the reservoirs, is rich in nutrients and plankton. As it flows through the Antoninek Reservoir it loses most of the phytoplanktonic organisms, measured as chlorophyll-a (70%), mostly due to the shading effect of emergent vegetation. The fraction autotrophic picoplankton (APP) also decreased considerably, both in numbers and biomass (about 68% and 54% on average, respectively). A similar reduction was recorded for the numbers of bacterioplankton (39% on average) and suspended solids (66%). Phytoplankton growth was observed again in the Maltański Reservoir, due to the longer residence time of water and lack of macrophytes. Chlorophyll-a increased by 37%, APP numbers by 120%, their biomass by 154%, while the numbers of bacterioplankton only by 31%. Changes in plankton abundance and biomass as a result of retention of water in a shallow reservoir influenced the quality of outflowing water. Their range strongly depended on the presence of macrophytes within the reservoir.
This paper presents the results of resarch on impact of humic substances (HS) on bacterioplancton in eutrophic Lake Jeziorak (north-eastern Poland). In cultures of natural bacteria from the lake water, enriched with 0, 5, 10, 25 and 50 mg dm⁻³ of HS (natural HS – isolated from lake water or commercial HS – sodium salt of humic substance; Sigma-Aldrich), were determined the following parameters: total number of bacteria (TNB), number of heterotrophic bacteria (CFU), bacterial production (BP) (measured with [³H]methyl thymidine method) and general activity of esterases. Natural HS had a more positive impact on bacterial growth, bacterial production and activity of esterases than the commercial preparation HS. The highest TNB and CFU was observed when the water was enriched with 25 mg dm⁻³ of natural HS. All concentrations of the natural HS stimulated bacterial production. The activity of hydrolytic enzymes increased with rising concentrations of natural HS.
The total numbers and biomass of bacterioplankton in two Arctic glacial fjords off west Spitsbergen were studied. Samples were collected from different water depth layers - from the surface to 80-90 m depth. Total bacterial number (TBN), biomass and morphological structure (shape of bacteria) were determined using the acridine orange direct count method. The highest values of TBN and biomass in the water column were found in Kongsfjorden in the stations adjacent to Kongsbreen Glacier, and the lowest values in the outer part of the Krossfjorden. The local maxima of bacterioplankton were observed in water layers around pycnocline. The morphological structure was similar in all samples - the bacteria were dominated by rods (over 65%), followed by cocci (16-20%) and vibrios (11-15%).
The mathematical model that described the relationship between cell-count decay and storage time in fixed bacterioplankton samples from three Antarctic lakes of differing trophic status was determined after a one-year experiment. Bacterial density was estimated by epifluorescence microscopy. Cell count data fitted a negative exponential model in all three cases (p < 0.00001). However, the slopes of their curves were significantly different (p < 0.01), as well as the percentage of bacterial loss after a period of two months. This fact might be related to the limnological characteristics of the water bodies, though the individual genetic variability of their bacterioplankton should not be left aside. Original bacterial numbers in the samples could also be a reason of the differences observed in the pattern of decay in cell counts. Thus, applying a general decay function to any sample and assuming the idea that freshwater bacterioplankton samples can be stored for a two month-period before the bacterial counts decay, can lead to an erroneous estimation of bacterial numbers with direct consequences in ecological investigations.
This study compared the outcome of photosensitization on the viability of four different cariogens in planktonic form as well as biofilms in human dentine. Photodynamic therapy was carried out with a gallium aluminium arsenide laser (670 nm wavelength) using Toluidine blue O (TBO) as the photosensitizer. Cariogenic bacteria (Streptococcus mutans, Lactobacillus casei, Streptococcus salivarius and Actinomyces viscosus) were exposed to TBO and then to the laser for 1 minute in planktonic suspension. Then, tooth slices previously incubated for 24 hours with broth cultures of broth culture of the four cariogenic organisms were exposed to antimicrobial photosensitization. The control samples consisted of planktonic and sessile cells that were exposed to TBO alone, laser alone and the bacterial cells that were not treated with TBO or laser. The results showed significant reductions in the viability of S. mutans, L.casei and A. viscosus in both planktonic form (to 13%, 30%, and 55%, respectively) and sessile form hosted in dentinal tubules (to 19%, 13% and 52%, respectively), relative to the controls. S.salivarius was the least affected in planktonic (94% viability) and sessile form (86% viability). In conclusion, sensitivity to photosensitization is species-dependent and sessile biofilm cells are affected to the same extent as their planktonic counterparts.
Antibiotic resistance of heterotrophic bacteria isolated from the surface microlayer and subsurface water of downtown pond was determined. The levels of resistance of bacteria to various antibiotics differed considerably. It follows from the results that bacteria were most resistant to penicillin and sensitive to gentamycin, neomycin and oxytetracycline. Majority of bacterial strains were characterised by resistance to 6-8 of 18 antibiotics tested. As a rule, there were no significant differences in antibiotic resistance between neustonic and planktonic bacteria. Pigmented bacteria were more antibiotic resistant than non-pigmented ones.
Floodplains are lateral river extensions in which lotic, semi-lotic and lentic habitats are formed resulting in high habitat heterogeniety. Consequently biota development is highely influenced by its location within the floodplain and by the hydrological cycle. In the present paper the development of planktonic and biofilm bacteria associated with artificial substrates were investigated in the floodplain lake of the Danube River (Lake Sakadaš, Croatia) during different hydrological situations. The aim of the study was to investigate if there was any difference in the bacterial development between two compartments – plankton and biofilm, and how the floods influence these communities. The samples were taken monthly (July–November 2007) from surface and bottom water layer (plankton) and exposed glass slides (biofilm) at two sampling stations. For these purposes bacterial abundance was estimated by the determination of number of colony forming units (CFUs). The development of bacterioplankton was equal between the sites and had its maximum at the time of falling water after the flood pulse. Bacterioplankton abundance correlated significantly with water properties, and it had predictable dynamics comparable with the previous results established in the same floodplain area (Kopački Rit). The development of biofilm bacteria differed between the sites, and had its maximum prior to the flood pulse, or during the flood. The abundance of attached bacteria correlated with biofilm biomass while it was not significantly correlated with the water properties. Such results describe different development of planktonic and biofilm bacteria. Biofilm bacteria are more independent, compared to bacterioplankton, from the floodplain hydrology.
The research was carried out in Lake Piecki and Lake Nawionek, two lobelia lakes located within the Zaborski Landscape Park. Water samples were collected from the surface and bottom water layers in spring, summer and autumn 2009. The analysis reveals that the total number of planktonic bacteria (TNB) in Lake Nawionek ranged between 8.83 and 36.22·10⁵ cells/cm³ and between 15.77 and 44.93·10⁵ cells/cm³ in Lake Piecki. The highest counts of bacteria were noted in spring. In a majority of tests heterotrophic psychrophilic bacteria (CFU 22℃) were more abundant in the surface water layer while heterotrophic mesophilic bacteria were always more abundant in the bottom water layer. Rods were prevailing morphological forms in both lakes, followed by pleomorphic forms, whereas cocci and bacilli constituted the least abundant microbial groups. Furthermore, ammonifying and nitrifying bacteria were the most common physiological forms in both lakes. Higher physiological activities of bacterial strains were observed in Lake Piecki with the exception of pectinolytic and ureolytic bacteria, which were more active in Lake Nawionek.
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