Journal articles on the topic 'Microcosm'
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Gagliardi, Joel V., J. Scott Angle, James J. Germida, R. Campbell Wyndham, Christopher P. Chanway, Robert J. Watson, Charles W. Greer, et al. "Intact soil-core microcosms compared with multi-site field releases for pre-release testing of microbes in diverse soils and climates." Canadian Journal of Microbiology 47, no. 3 (March 1, 2001): 237–52. http://dx.doi.org/10.1139/w00-142.
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Intact soil-core microcosms were used to compare persistence of Pseudomonas chlororaphis 3732RN-L11 in fallow soil and on wheat roots with field releases at diverse sites. Parallel field and microcosm releases at four sites in 1996 were repeated with addition of one site in 1997. Microcosms were obtained fresh and maintained at 60% soil water holding capacity in a growth chamber at 70% relative humidity, a 12-hour photoperiod, and constant temperature. Persistence of 3732RN-L11 was measured at each site in field plots and microcosms at 721 day intervals, and in duplicate microcosms sampled at an independent laboratory. Linear regression slopes of field plot and microcosm persistence were compared for each site, and between identical microcosms sampled at different sites, using log10transformed plate counts. Microcosm persistence closely matched field plots for wheat roots, but persistence in fallow soil differed significantly in several instances where persistence in field plots was lower than in microcosms. Analysis of weather variations at each site indicated that rainfall events of 3040 mm caused decreased persistence in fallow soil. Cooler temperatures enhanced persistence in field plots at later time points. Inter-laboratory comparison of regression slopes showed good agreement for data generated at different sites, though in two instances, longer sampling periods at one site caused significant differences between the sites. Soil characteristics were compared and it was found that fertility, namely the carbon to nitrogen ratio, and the presence of expanding clays, were related to persistence. These microcosm protocols produced reliable data at low cost, and were useable for pre-release risk analyses for microorganisms.Key words: microcosm, soil, microbiology, risk assessment, 3732RN-L11.
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Kim, Youngjun, Sangeun Park, and Seungdae Oh. "Machine Learning Approach Reveals the Assembly of Activated Sludge Microbiome with Different Carbon Sources during Microcosm Startup." Microorganisms 9, no. 7 (June 25, 2021): 1387. http://dx.doi.org/10.3390/microorganisms9071387.
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Activated sludge (AS) microcosm experiments usually begin with inoculating a bioreactor with an AS mixed culture. During the bioreactor startup, AS communities undergo, to some extent, a distortion in their characteristics (e.g., loss of diversity). This work aimed to provide a predictive understanding of the dynamic changes in the community structure and diversity occurring during aerobic AS microcosm startups. AS microcosms were developed using three frequently used carbon sources: acetate (A), glucose (G), and starch (S), respectively. A mathematical modeling approach quantitatively determined that 1.7–2.4 times the solid retention time (SRT) was minimally required for the microcosm startups, during which substantial divergences in the community biomass and diversity (33–45% reduction in species richness and diversity) were observed. A machine learning modeling application using AS microbiome data could successfully (>95% accuracy) predict the assembly pattern of aerobic AS microcosm communities responsive to each carbon source. A feature importance analysis pinpointed specific taxa that were highly indicative of a microcosm feed source (A, G, or S) and significantly contributed for the ML-based predictive classification. The results of this study have important implications on the interpretation and validity of microcosm experiments using AS.
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Ohno, Akira, Naoyuki Kato, Koji Yamada, and Keizo Yamaguchi. "Factors Influencing Survival of Legionella pneumophila Serotype 1 in Hot Spring Water and Tap Water." Applied and Environmental Microbiology 69, no. 5 (May 2003): 2540–47. http://dx.doi.org/10.1128/aem.69.5.2540-2547.2003.
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ABSTRACT The factors involved in the survival of Legionella pneumophila in the microcosms of both hot spring water and tap water were studied by examining cultivability and metabolic activity. L. pneumophila could survive by maintaining metabolic activity but was noncultivable in all microcosms at 42°C, except for one microcosm with a pH of <2.0. Lower temperatures supported survival without loss of cultivability. The cultivability declined with increasing temperature, although metabolic activity was observed at temperatures of up to 45°C. The optimal range of pH for survival was between 6.0 and 8. The metabolic activity could be maintained for long periods even in microcosms with high concentrations of salt. The cultivability of organisms in the post-exponential phase in a tap water microcosm with a low inoculum size was more rapidly reduced than that of organisms in the exponential phase. In contrast, the loss of cultivability in microcosms of a high inoculum size was significant in the exponential phase. Random(ly) amplified polymorphic DNA analysis of microcosms where cultivability was lost but metabolic activity was retained showed no change compared to cells grown freshly, although an effect on the amplified DNA band pattern by production of stress proteins was expected. Resuscitation by the addition of Acanthamoeba castellanii to the microcosm in which cultivability was completely lost but metabolic activity was maintained was observed only in part of the cell population. Our results suggest that L. pneumophila cell populations can potentially survive as free organisms for long periods by maintaining metabolic activity but temporarily losing cultivability under strict environments and requiring resuscitation by ingestion by amoebas.
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Taylor, Barry, and Dennis Parkinson. "A new microcosm approach to litter decomposition studies." Canadian Journal of Botany 66, no. 10 (October 1, 1988): 1933–39. http://dx.doi.org/10.1139/b88-265.
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Microcosms, simplified analogues of natural ecosystems, are a useful tool for studies of litter decomposition. A literature review shows that if microcosms are carefully constructed to mimic nature accurately, they allow researchers to control and independently vary normally covarying environmental factors (temperature, moisture, soil animals) that influence decomposition rates, while maintaining a sufficiently natural situation so that results of laboratory tests may be extrapolated to the field situation with confidence. A simple, inexpensive system of laboratory microcosms for decomposition studies is described and evaluated in this paper. The microcosm, housed within an airtight PVC chamber, consists of a litter layer overlying a core of forest floor strata collected with a minimum of disturbance to physical structure and populations of soil organisms. The microcosms have been tested with soil and litter from an aspen woodland and a pine forest, at temperatures ranging from −6 to +26 °C, and have been maintained in the laboratory for up to 6 months without significant deterioration. The microcosm system provided decomposition estimates that were precise, replicable, and rapidly obtained by measuring either mass loss or CO2 efflux from litter samples. Problems with the method include rapid increases in populations of some soil animals, difficulty in controlling relative humidity, and acceleration of decay rates compared with those in litter in the field.
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Rebecca Cook. "MICROCOSM." Antioch Review 71, no. 4 (2013): 695. http://dx.doi.org/10.7723/antiochreview.71.4.0695.
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Nataro, James P. "Microcosm." Journal of Clinical Investigation 118, no. 12 (December 1, 2008): 3818. http://dx.doi.org/10.1172/jci37541.
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Tkaczynska, A. "Removal of As from groundwater by in situ bioprecipitation and zero-valent iron." Water Science and Technology 68, no. 9 (October 19, 2013): 2055–60. http://dx.doi.org/10.2166/wst.2013.462.
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The aim of this study was to evaluate the in situ bioprecipitation (ISBP) and zero-valent iron (ZVI) for removal of arsenic from groundwater. Batch experiments were set up to test the metal/oxyanion removal efficiency using the processes induced by ZVI, by ISBP and by combining both technologies. For the construction of microcosms in anaerobic condition, aquifer material was mixed with synthetic groundwater in serum bottles. Solutions that contained commercial iron (powder, filings), iron from foundry (chips) and lactate with the carbon concentration of 0.02% (w/v) were amended. After 57 days the pH increased to 7.9 in the microcosm with lactate + iron chips. In the microcosms amended with lactate + commercial iron (powder and filings), pH was between 6.9 and 7.5 The highest decrease in sulfate concentrations was observed in the microcosm supplied with lactate (from 1,976 to 630 mg/L), and with lactate + iron filings (from 1,985 to 1,280 mg/L). The results showed that ISBP and ZVI can be efficient in the removal of As from groundwater; however, it strongly depends on the type and particle size of ZVI. The most effective was commercial ZVI. The highest decrease in As concentration was observed in the microcosm supplied with ethanol and iron powder (from 4,832 to 131 μg/L).
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Cheriaa, Jihane, Mahmoud Rouabhia, Makaoui Maatallah, and Amina Bakhrouf. "Phenotypic stress response of Pseudomonas aeruginosa following culture in water microcosms." Journal of Water and Health 10, no. 1 (March 1, 2012): 130–39. http://dx.doi.org/10.2166/wh.2011.072.
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The purpose of the present study was to explore the potential behavioural changes of Pseudomonas aeruginosa following growth in different aquatic environmental conditions. To achieve this, P. aeruginosa was cultured in various water microcosms for 12 months under fixed (pH, nutrients and temperature) factors. P. aeruginosa responses to these conditions were investigated using colony morphotype, biochemical and enzymatic characterisation, pyocin typing, serotyping, sensitivity to different classes of antibiotics and molecular identification. Results show that starvation in water microcosms lead to unusual phenotypes. Of interest is that the pyocin changed from 24/n in the wild type to 83/a following culture in the water microcosms, and the serotype changed from O6 in the wild type to O1 in microcosm-cultured P. aeruginosa. Furthermore, the starvation period in various aquatic microcosms enhanced the resistance of P. aeruginosa against beta-lactam antibiotics. Compared to the other aquatic environments, the seawater microcosm produced the greatest amount of variations in P. aeruginosa. Overall, data demonstrated a high adaptability of P. aeruginosa to environmental changes. This may explain the unusual antibiotic-resistant phenotypes belonging to P. aeruginosa species, and their capacity for spreading that leads to human infections.
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Ch’ng, Boon-Lek, Che-Jung Hsu, Yu Ting, Ying-Lin Wang, Chi Chen, Tien-Chin Chang, and Hsing-Cheng Hsi. "Aqueous Mercury Removal with Carbonaceous and Iron Sulfide Sorbents and Their Applicability as Thin-Layer Caps in Mercury-Contaminated Estuary Sediment." Water 12, no. 7 (July 14, 2020): 1991. http://dx.doi.org/10.3390/w12071991.
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This study aimed to investigate the Hg removal efficiency of iron sulfide (FeS), sulfurized activated carbon (SAC), and raw activated carbon (AC) sorbents influenced by salinity and dissolved organic matter (DOM), and the effectiveness of these sorbents as thin layer caps on Hg-contaminated sediment remediation via microcosm experiments to decrease the risk of release. In the batch adsorption experiments, FeS showed the greatest Hg2+ removal efficiencies, followed by SAC and AC. The effect of salinity levels on FeS was insignificant. In contrast, the Hg2+ removal efficiency of AC and SAC increased as increasing the salinity levels. The presence of DOM tended to decrease Hg removal efficiency of sorbents. Microcosm studies also showed that FeS had the greatest Hg sorption in both freshwater and estuary water; furthermore, the methylmercury (MeHg) removal ability of sorbents was greater in the freshwater than that in the estuary water. Notably, for the microcosms without capping, the overlying water MeHg in the estuary microcosm (0.14−1.01 ng/L) was far lesser than that in the freshwater microcosms (2.26−11.35 ng/L). Therefore, Hg compounds in the freshwater may be more bioavailable to microorganisms in methylated phase as compared to those in the estuary water. Overall, FeS showed the best Hg removal efficiency, resistance to salinity, and only slightly affected by DOM in aqueous adsorption experiments. Additionally, in the microcosms, AC showed as the best MeHg adsorber that help inhibiting the release of MeHg into overlying and decreasing the risk to the aqueous system.
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Montmollin, Olivier de. "Tenam Rosario—A Political Microcosm." American Antiquity 53, no. 2 (April 1988): 351–70. http://dx.doi.org/10.2307/281024.
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Civic-ceremonial plaza planning is analyzed at Tenam Rosario, the capital center of a small Late/Terminal Classic period (A.D. 700-950) Maya polity, to shed light on political organization. When the capital's civic-ceremonial layout is compared with settlement patterns in its hinterland, the polity's hierarchical and territorial political arrangements appear to be reproduced in microcosm within the capital"s civic-ceremonial zone. Possible political microcosms of this kind at other mesoamerican capital sites are discussed, along with correlates of this variant of political organization.
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Guan, J., J. L. Spencer, M. Sampath, and J. Devenish. "The fate of a genetically modifiedPseudomonasstrain and its transgene during the composting of poultry manure." Canadian Journal of Microbiology 50, no. 6 (June 1, 2004): 415–21. http://dx.doi.org/10.1139/w04-030.
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The fate of the genetically modified (GM) Pseudomonas chlororaphis strain 3732 RN-L11 and its transgene (lacZ insert) during composting of chicken manure was studied using plate count and nested polymerase chain reaction (PCR) methods. The detection sensitivity of the nested PCR method was 165 copies of the modified gene per gram of moist compost or soil. Compost microcosms consisted of a 100-g mixture of chicken manure and peat, whereas soil microcosms were 100-g samples of sandy clay loam. Each microcosm was inoculated with 4 × 1010CFU of P. chlororaphis RN-L11. In controlled temperature studies, neither P. chlororaphis RN-L11 nor its transgene could be detected in compost microcosms after incubation temperature was elevated to 45 °C or above for one or more days. In contrast, in the compost microcosms incubated at 23 °C, the target organism was not detected by the plate count method after 6 days, but its transgene was detectable for at least 45 days. In compost bins, the target organism was not recovered from compost microcosms or soil microcosms at different levels in the bins for 29 days. However, the transgene was detected in 8 of the 9 soil microcosms and in only 1 of the 9 compost microcosms. The compost microcosm in which transgene was detected was at the lower level of the bin where temperatures remained below 45 °C. The findings indicated that composting of organic wastes could be used to reduce or degrade heat sensitive GM microorganisms and their transgenes.Key words: composting, genetically modified Pseudomonas strain, transgene, polymerase chain reaction.
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Jones, Elizabeth J. P., Mary A. Voytek, Margo D. Corum, and William H. Orem. "Stimulation of Methane Generation from Nonproductive Coal by Addition of Nutrients or a Microbial Consortium." Applied and Environmental Microbiology 76, no. 21 (September 3, 2010): 7013–22. http://dx.doi.org/10.1128/aem.00728-10.
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ABSTRACT Biogenic formation of methane from coal is of great interest as an underexploited source of clean energy. The goal of some coal bed producers is to extend coal bed methane productivity and to utilize hydrocarbon wastes such as coal slurry to generate new methane. However, the process and factors controlling the process, and thus ways to stimulate it, are poorly understood. Subbituminous coal from a nonproductive well in south Texas was stimulated to produce methane in microcosms when the native population was supplemented with nutrients (biostimulation) or when nutrients and a consortium of bacteria and methanogens enriched from wetland sediment were added (bioaugmentation). The native population enriched by nutrient addition included Pseudomonas spp., Veillonellaceae, and Methanosarcina barkeri. The bioaugmented microcosm generated methane more rapidly and to a higher concentration than the biostimulated microcosm. Dissolved organics, including long-chain fatty acids, single-ring aromatics, and long-chain alkanes accumulated in the first 39 days of the bioaugmented microcosm and were then degraded, accompanied by generation of methane. The bioaugmented microcosm was dominated by Geobacter sp., and most of the methane generation was associated with growth of Methanosaeta concilii. The ability of the bioaugmentation culture to produce methane from coal intermediates was confirmed in incubations of culture with representative organic compounds. This study indicates that methane production could be stimulated at the nonproductive field site and that low microbial biomass may be limiting in situ methane generation. In addition, the microcosm study suggests that the pathway for generating methane from coal involves complex microbial partnerships.
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Christison, Kathleen. "Macro Microcosm." Journal of Palestine Studies 21, no. 4 (1992): 98–100. http://dx.doi.org/10.2307/2537668.
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Wagner-Döbler, I., A. Bennasar, M. Vancanneyt, C. Strömpl, I. Brümmer, C. Eichner, I. Grammel, and E. R. B. Moore. "Microcosm Enrichment of Biphenyl-Degrading Microbial Communities from Soils and Sediments." Applied and Environmental Microbiology 64, no. 8 (August 1, 1998): 3014–22. http://dx.doi.org/10.1128/aem.64.8.3014-3022.1998.
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ABSTRACT A microcosm enrichment approach was employed to isolate bacteria which are representative of long-term biphenyl-adapted microbial communities. Growth of microorganisms was stimulated by incubating soil and sediment samples from polluted and nonpolluted sites with biphenyl crystals. After 6 months, stable population densities between 8 × 109 and 2 × 1011 CFU/ml were established in the microcosms, and a large percentage of the organisms were able to grow on biphenyl-containing minimal medium plates. A total of 177 biphenyl-degrading strains were subsequently isolated and characterized by their ability to grow on biphenyl in liquid culture and to accumulate a yellow meta cleavage product when they were sprayed with dihydroxybiphenyl. Isolates were identified by using a polyphasic approach, including fatty acid methyl ester (FAME) analysis, 16S rRNA gene sequence comparison, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins, and genomic fingerprinting based on sequence variability in the 16S-23S ribosomal DNA intergenic spacer region. In all of the microcosms, isolates identified as Rhodococcus opacus dominated the cultivable microbial community, comprising a cluster of 137 isolates with very similar FAME profiles (Euclidean distances, <10) and identical 16S rRNA gene sequences. The R. opacus isolates from the different microcosms studied could not be distinguished from each other by any of the fingerprint methods used. In addition, three other FAME clusters were found in one or two of the microcosms analyzed; these clusters could be assigned to Alcaligenessp., Terrabacter sp., and Bacillus thuringiensis on the basis of their FAME profiles and/or comparisons of the 16S rRNA gene sequences of representatives. Thus, the microcosm enrichments were strongly dominated by gram-positive bacteria, especially the species R. opacus, independent of the pollution history of the original sample. R. opacus, therefore, is a promising candidate for development of effective long-term inocula for polychlorinated biphenyl bioremediation.
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Duncan, Elliott G., William A. Maher, Simon D. Foster, Frank Krikowa, and Katarina M. Mikac. "The degradation of arsenoribosides from Ecklonia radiata tissues decomposed in natural and microbially manipulated microcosms." Environmental Chemistry 11, no. 3 (2014): 289. http://dx.doi.org/10.1071/en13155.
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Environmental context Arsenoribosides are the major arsenic species in marine macro-algae, yet inorganic arsenic is the major arsenic species found in seawater. We investigated the degradation of arsenoribosides associated with Ecklonia radiata by the use of microcosms containing both natural and autoclaved seawater and sand. The decomposition and persistence of arsenic species was linked to the use of autoclaved seawater and sand, which suggests that arsenoriboside degradation is governed by the microbial composition of microenvironments within marine systems. Abstract We investigated the influence of microbial communities on the degradation of arsenoribosides from E. radiata tissues decomposing in sand and seawater-based microcosms. During the first 30 days, arsenic was released from decomposing E. radiata tissues into seawater and sand porewaters in all microcosms. In microcosms containing autoclaved seawater and autoclaved sand, arsenic was shown to persist in soluble forms at concentrations (9–18µg per microcosm) far higher than those present initially (~3µg per microcosm). Arsenoribosides were lost from decomposing E. radiata tissues in all microcosms with previously established arsenoriboside degradation products, such as thio-arsenic species, dimethylarsinoylethanol (DMAE), dimethylarsenate (DMA) and arsenate (AsV) observed in all microcosms. DMAE and DMA persisted in the seawater and sand porewaters of microcosms containing autoclaved seawater and autoclaved sand. This suggests that the degradation step from arsenoribosides → DMAE occurs on algal surfaces, whereas the step from DMAE → AsV occurs predominantly in the water-column or sand–sediments. This study also demonstrates that disruptions to microbial connectivity (defined as the ability of microbes to recolonise vacant habitats) result in alterations to arsenic cycling. Thus, the re-cycling of arsenoribosides released from marine macro-algae is driven by microbial complexity plus microbial connectivity rather than species diversity as such, as previously assumed.
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Shi, Xiaoli, Xuhui Zhao, Min Zhang, Zhou Yang, Ping Xu, and Fanxiang Kong. "The responses of phytoplankton communities to elevated CO2 show seasonal variations in the highly eutrophic Lake Taihu." Canadian Journal of Fisheries and Aquatic Sciences 73, no. 5 (May 2016): 727–36. http://dx.doi.org/10.1139/cjfas-2015-0151.
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From April 2012 to January 2013 (over four seasons), in situ microcosm experiments were conducted in Lake Taihu, perturbed over a range of pCO2 scenarios (270, 380, and 750 μatm; 1 atm = 101.325 kPa). The influence of CO2 level on microcosms was greatest during the spring because of the high growth rate of phytoplankton. In this season, rising CO2 levels caused a pH reduction, and the maximum reduction was 0.6 units when CO2 level was enhanced from the present level to 750 μatm. The doubling of CO2 level could increase the net primary production (NPP) by 65% during spring when the concentrations of other nutrients were maintained. The rise of NPP could cause a decline of dissolved inorganic carbon (DIC) concentration, and CO2 enrichment might mitigate the extent of this decline. Meanwhile, higher CO2 may slow or prevent a loss of diversity of phytoplankton in microcosms in this season. During the other three seasons, Microcystis predominated, and the percentage of cyanobacteria did not alter with the change of CO2. We did not observe a significant increase in the abundance of any taxa with the rise of CO2 during the in situ microcosm experiments.
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Russo, Ferguson, Beckerman, and Pandhal. "Structural Equation Modelling Reveals That Nutrients and Physicochemistry Act Additively on the Dynamics of a Microcosm-Based Biotic Community." Biology 8, no. 4 (November 14, 2019): 87. http://dx.doi.org/10.3390/biology8040087.
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Anthropogenic eutrophication has caused widespread environmental problems in freshwater lakes, reducing biodiversity and disrupting the classic pelagic food chain. Increasing our understanding of the exact role of nutrients and physicochemical variables on microbial dynamics, and subsequent microalgal and cyanobacterial blooms, has involved numerous studies ranging from replicate microcosm-based studies through to temporal studies of real lake data. In a previous experimental microcosm study, we utilised metaproteomics to investigate the functional changes of a microalgal-bacterial community under oligotrophic and eutrophic nutrient levels. Here, we analyse the time series data from this experiment with a combination of typically used univariate analyses and a more modern multivariate approach, structural equation modelling. Our aim was to test, using these modern methods, whether physicochemical variables and nutrient dynamics acted additively, synergistically, or antagonistically on the specific biotic community used in the microcosms. We found that nutrients (nitrogen and phosphorus) and temperature acted additively on the interactions between the microalgae and bacteria present, with the temperature effects elevated in the eutrophic conditions we applied. The data suggests that there may be no synergistic interaction between nutrients and temperature in the tested microcosms. Our approach demonstrates how the application of multivariate methods to existing datasets, in our case from nutrient-enriched freshwater microcosms, enables new information to be extracted, enhancing interpretations as well as allowing more reliable comparisons to similar published studies.
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Furtak, Karolina, Jarosław Grządziel, and Anna Gałązka. "Can Model Experiments Give Insight into the Response of the Soil Environment to Flooding? A Comparison of Microcosm and Natural Event." Biology 11, no. 3 (March 1, 2022): 386. http://dx.doi.org/10.3390/biology11030386.
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Studies using soil microcosms are very common, but few involve flooded soils, and comparing the results from such an experiment with natural conditions is unheard of. In the present study, we investigated the biological activity of soil (pH value, dehydrogenases and phosphatase activities) and the metabolic potential (EcoPlate™ Biolog®) of soil microorganisms in three fluvisol subjected to flooding under laboratory and natural conditions. The results indicate that soil flooding under both natural and laboratory conditions affected soil pH, enzymatic activity and metabolic potential (AWCD, average well colour development) of soil microorganisms. Changes in these parameters are more pronounced in the microcosmic experiment than in the field conditions. Furthermore, depending on the characteristics of the soil (i.e., its type, structure, vegetation) some of the soil quality parameters may return to their preflood state. Microcosm studies are needed in environmental ecology and microbiology to predict changes due to various factors, but their scale and course must be carefully planned.
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Yoshida, Naoko, Nobutaka Takahashi, and Akira Hiraishi. "Phylogenetic Characterization of a Polychlorinated-Dioxin- Dechlorinating Microbial Community by Use of Microcosm Studies." Applied and Environmental Microbiology 71, no. 8 (August 2005): 4325–34. http://dx.doi.org/10.1128/aem.71.8.4325-4334.2005.
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ABSTRACT Microcosms capable of reductive dechlorination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) were constructed in glass bottles by seeding them with a polluted river sediment and incubating them anaerobically with an organic medium. All of the PCDD/F congeners detected were equally reduced without the accumulation of significant amounts of less-chlorinated congeners as the intermediate or end products. Alternatively, large amounts of catechol and salicylic acid were produced in the upper aqueous phase. Thus, the dechlorination of PCDD/Fs and the oxidative degradation of the dechlorinated products seemed to take place simultaneously in the microcosm. Denaturing gel gradient electrophoresis and clone library analyses of PCR-amplified 16S rRNA genes from the microcosm showed that members of the phyla Firmicutes, Proteobacteria, and Bacteroidetes predominated. A significant number of Chloroflexi clones were also detected. Quantitative real-time PCR with specific primer sets showed that the 16S rRNA genes of a putative dechlorinator, “Dehalococcoides,” and its relatives accounted for 0.1% of the total rRNA gene copies of the microcosm. Most of the clones thus obtained formed a cluster distinct from the typical “Dehalococcoides” group. Quinone profiling indicated that ubiquinones accounted for 18 to 25% of the total quinone content, suggesting the coexistence and activity of ubiquinone-containing aerobic bacteria. These results suggest that the apparent complete dechlorination of PCDD/Fs found in the microcosm was due to a combination of the dechlorinating activity of the “Dehalococcoides”-like organisms and the oxidative degradation of the dechlorinated products by aerobic bacteria with aromatic hydrocarbon dioxygenases.
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Maïga, Ynoussa, Joseph Wethe, Kokou Denyigba, and Aboubakar Sidiki Ouattara. "The impact of pond depth and environmental conditions on sunlight inactivation of Escherichia coli and enterococci in wastewater in a warm climate." Canadian Journal of Microbiology 55, no. 12 (December 2009): 1364–74. http://dx.doi.org/10.1139/w09-104.
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Microcosm experiments were carried out under dark and real sunlight conditions in Ouagadougou (Burkina Faso) to investigate the survival of faecal indicators ( Escherichia coli and enterococci) in secondary wastewater. Light damage was estimated by loss of bacterial culturability. The results clearly show that sunlight has a deleterious effect on the survival of both indicators. The mean dark inactivation coefficients for E. coli and enterococci were 0.045 and 0.047 h–1,respectively, whereas inactivation coefficients in the shallowest microcosm (0.1 m) in illuminated conditions were 0.796 and 0.559 h–1, respectively. No significant effect of pond depth (0.1–0.9 m) on the inactivation of both indicators was observed in the dark. However, the effect of depth was significant in the microcosms exposed to sunlight, probably because of attenuation. In illuminated conditions, enterococci were broadly inactivated more rapidly than E. coli (T90 = 26.81 h for E. coli and 15.67 h for enterococci in the 0.4 m microcosm). However, E. coli presented greater variability in the survival capabilities, suggesting difficulties in interpreting data using only E. coli as an indicator. Therefore, the use of both indicators together should be advisable for the assessment of effluent quality from waste stabilization ponds in the Sahelian region.
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Wang, Kai, and Xiaozhen Mou. "Coordinated Diel Gene Expression of Cyanobacteria and Their Microbiome." Microorganisms 9, no. 8 (August 5, 2021): 1670. http://dx.doi.org/10.3390/microorganisms9081670.
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Diel rhythms have been well recognized in cyanobacterial metabolisms. However, whether this programmed activity of cyanobacteria could elicit coordinated diel gene expressions in microorganisms (microbiome) that co-occur with cyanobacteria and how such responses in turn impact cyanobacterial metabolism are unknown. To address these questions, a microcosm experiment was set up using Lake Erie water to compare the metatranscriptomic variations of Microcystis cells alone, the microbiome alone, and these two together (whole water) over two day-night cycles. A total of 1205 Microcystis genes and 4779 microbiome genes exhibited significant diel expression patterns in the whole-water microcosm. However, when Microcystis and the microbiome were separated, only 515 Microcystis genes showed diel expression patterns. A significant structural change was not observed for the microbiome communities between the whole-water and microbiome microcosms. Correlation analyses further showed that diel expressions of carbon, nitrogen, phosphorous, and micronutrient (iron and vitamin B12) metabolizing genes were significantly coordinated between Microcystis and the microbiome in the whole-water microcosm. Our results suggest that diel fluxes of organic carbon and vitamin B12 (cobalamin) in Microcystis could cause the diel expression of microbiome genes. Meanwhile, the microbiome communities may support the growth of Microcystis by supplying them with recycled nutrients, but compete with Microcystis for iron.
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Lebaron, P., P. Bauda, N. Frank, M. C. Lett, B. Roux, J. C. Hubert, Y. Duval-Iflah, et al. "Recombinant plasmid mobilization betweenE.colistrains in seven sterile microcosms." Canadian Journal of Microbiology 43, no. 6 (June 1, 1997): 534–40. http://dx.doi.org/10.1139/m97-076.
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Transfer by mobilization of a pBR derivative recombinant plasmid lacking transfer functions (oriT+, tra−, mob−) from one E. coli K12 strain to another was investigated in seven sterile microcosms corresponding to different environments. These microcosms were chosen as representative of environments that genetically engineered microorganisms (GEMOs) encounter after accidental release, namely attached biomass in aquatic environments (biofilm), soil, seawater, freshwater, wastewater, mouse gut, and mussel gut. GEMOs survived in the same way as the host strains in all microcosms. Recombinant DNA mobilization occurred in the mouse gut, in sterile soil, and in biofilm. The plasmid transfer rates principally reflected the environmental conditions encountered in each microcosm.Key words: recombinant DNA, plasmid transfer, mobilization, conjugation, microcosm.
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Schmidt, K. R., and A. Tiehm. "Natural attenuation of chloroethenes: identification of sequential reductive/oxidative biodegradation by microcosm studies." Water Science and Technology 58, no. 5 (September 1, 2008): 1137–45. http://dx.doi.org/10.2166/wst.2008.729.
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A different lines of evidence approach for investigation of biodegradation processes at a chloroethene contaminated site showed well corresponding results of pollutant profiles, redox zonation, characterisation of autochthonic microflora and microcosm studies. In particular microcosm studies allowed identification of the predominating degradation pathways. Perchloroethene and trichloroethene are reductively chlorinated to mainly cis-1,2-dichloroethene (cDCE) under anaerobic conditions. Further reductive degradation to vinyl chloride (VC) is restricted to a distinct strongly anaerobic zone in the plume. Addition of high amounts of sediment material (80 vol%) to groundwater microcosms enabled reductive dechlorination without amendment with further auxiliary substrates. Reductive dechlorination was not irreversibly hindered by initially high nitrate concentrations and initially high oxidation–reduction potential. The products of anaerobic degradation cDCE and VC are subsequently aerobically mineralised, even when only low oxygen concentrations are available. Anaerobic oxidative degradation could not be proven in this study.
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Stringfellow, William T., M. Ekrem Karpuzcu, Chelsea Spier, Jeremy S. Hanlon, and Justin Graham. "Sizing mitigation wetlands in agricultural watersheds." Water Science and Technology 67, no. 1 (January 1, 2013): 40–46. http://dx.doi.org/10.2166/wst.2012.527.
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In this study, we investigated use of microcosms to supplement field studies for establishing the size of wetlands required to mitigate nitrate pollution in agricultural watersheds. Wetlands investigated in this study were located in San Joaquin Valley (California, USA) and demonstrated mean nitrate-nitrogen mass removal efficiencies ranging between 10 and 34%. Mean areal nitrate removal rates (J) ranged from 142 to 380 mg-N m−2 d−1. First-order rate constants determined from field data had a high variance, with confidence intervals greater than 57% of mean values. Sediments and rooted plants from one site were placed in a flow-through microcosm and measurements of nitrate removal kinetics were made and compared with field results. The apparent half-saturation constant (Km) and maximum removal rate (Jmax) for nitrate-nitrogen were 43.8 mg/L and 4.11 g m−2 d−1 in the microcosm. The first-order rate constant from the microcosm (10.4 cm d−1) was in close agreement with the value for the field site (11.9 cm d−1) and had a confidence interval of less than 16%. Using this improved first-order rate constant, it was determined that between 1.3 and 3.6% of the land in the watershed should be managed as mitigation wetland, with the area required dependent on the level of nitrate reduction desired and how closely the wetland design approximates plug-flow.
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Karunarathna, A. K., N. Tanaka, and K. B. S. N. Jinadasa. "Effect of external organic matter on nutrient removal and growth of Phragmites australis in a laboratory-scale subsurface-flow treatment wetland." Water Science and Technology 55, no. 1-2 (January 1, 2007): 121–28. http://dx.doi.org/10.2166/wst.2007.030.
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Coconut dust, which is used intensively in horticultural applications, was tested as an external organic additive in a series of laboratory-scale subsurface-flow constructed wetlands planted with Phragmites australis. The systems were fed with a mixture of NO−3-N, NH+4-N, and SRP in tap water to simulate high nutrient loads. In the absence of plants, TN removal efficiency was 66%, and the efficiency increased to >80% in the microcosm wetlands. TN and NO−3 removal efficiencies were marginally increased by coconut-dust treatment in comparison with sand-bed microcosms. Analysis by ANOVA showed that the TN removal from a coconut dust-supplemented sand-bed microcosm was significantly different from a sand-bed microcosm (0.0437 < p<0.05). All the systems showed an equal capacity to treat NH+4 nitrogen under low influent concentration levels. Phosphorus removal efficiencies were >98% in all three systems, and a difference between planted and unplanted systems was not observed. Shoot height and shoot densities of P. australis grown in the coconut dust-supplemented medium were significantly higher than those grown in the sand-bed medium. The difference in P. australis growth in response to the coconut dust addition revealed that the added material has the potential to create favourable conditions for plant growth.
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Kikkawa, J. "Microcosm food webs." Trends in Ecology & Evolution 16, no. 6 (June 1, 2001): 322. http://dx.doi.org/10.1016/s0169-5347(01)02129-2.
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Halmi, Nicholas. "Mind as microcosm." European Romantic Review 12, no. 1 (January 2001): 43–52. http://dx.doi.org/10.1080/10509580108570126.
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Nercessian, Olivier, Emma Noyes, Marina G. Kalyuzhnaya, Mary E. Lidstrom, and Ludmila Chistoserdova. "Bacterial Populations Active in Metabolism of C1 Compounds in the Sediment of Lake Washington, a Freshwater Lake." Applied and Environmental Microbiology 71, no. 11 (November 2005): 6885–99. http://dx.doi.org/10.1128/aem.71.11.6885-6899.2005.
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ABSTRACT Active members of the bacterial community in the sediment of Lake Washington, with special emphasis on C1 utilizers, were identified by employing two complementary culture-independent approaches: reverse transcription of environmental mRNA and 16S rRNA combined with PCR (RT-PCR) and stable-isotope probing (SIP) of DNA with the 13C-labeled C1 substrates methanol, methylamine, formaldehyde, and formate. Analysis of RT-PCR-amplified fragments of 16S rRNA-encoding genes revealed that gammaproteobacterial methanotrophs belonging to Methylobacter and Methylomonas dominate the active methylotroph population, while only one other known methylotrophic lineage, Methylophilaceae, was detected via this approach. Analysis of RT-PCR-amplified functional genes, pmoA and fae, allowed detection of alphaproteobacterial (Methylosinus) and gammaproteobacterial (Methylobacter, Methylomonas, and Methylomicrobium) methanotrophs, methylotrophs of the genus Methylobacterium, and yet-unidentified proteobacteria. SIP experiments allowed detection of a broad variety of groups actively metabolizing C1 compounds. Comparisons between 16S rRNA gene pools amplified from [13C]DNA and from [12C]DNA revealed that the proportion of Methylophilus-related sequences increased in the presence of [13C]methanol, [13C]methylamine, and [13C]formaldehyde; Novosphingobium-related sequences were enriched in the presence of [13C]methanol; Gemmatimonadaceae-related sequences were enriched in the presence of [13C]formaldehyde and [13C]formate; and Xanthomonadaceae-related sequences were enriched in the presence of [13C]formate. Analysis of fae genes amplified from [13C]DNAs isolated from different microcosms revealed specific shifts in populations in response to a specific C1 compound: Methylosinus sequences dominated the [13C]methanol microcosm pool, and beta- and gammaproteobacterial sequences dominated the [13C]methylamine microcosm pool. The [13C]formaldehyde microcosm was dominated by betaproteobacterial sequences and by sequences of a nonaffiliated group, while the [13C]formate microcosm was dominated by alpha- and betaproteobacterial sequences. Overall, these data point toward the presence of a diverse population of active methylotrophs in Lake Washington sediments and toward the existence of yet-uncultivated organisms.
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Shi, Y., M. D. Zwolinski, M. E. Schreiber, J. M. Bahr, G. W. Sewell, and W. J. Hickey. "Molecular Analysis of Microbial Community Structures in Pristine and Contaminated Aquifers: Field and Laboratory Microcosm Experiments." Applied and Environmental Microbiology 65, no. 5 (May 1, 1999): 2143–50. http://dx.doi.org/10.1128/aem.65.5.2143-2150.1999.
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ABSTRACT This study used phylogenetic probes in hybridization analysis to (i) determine in situ microbial community structures in regions of a shallow sand aquifer that were oxygen depleted and fuel contaminated (FC) or aerobic and noncontaminated (NC) and (ii) examine alterations in microbial community structures resulting from exposure to toluene and/or electron acceptor supplementation (nitrate). The latter objective was addressed by using the NC and FC aquifer materials for anaerobic microcosm studies in which phylogenetic probe analysis was complemented by microbial activity assays. Domain probe analysis of the aquifer samples showed that the communities were predominantlyBacteria; Eucarya and Archaea were not detectable. At the phylum and subclass levels, the FC and NC aquifer material had similar relative abundance distributions of 43 to 65% β- and γ-Proteobacteria (B+G), 31 to 35% α-Proteobacteria (ALF), 15 to 18% sulfate-reducing bacteria, and 5 to 10% high G+C gram positive bacteria. Compared to that of the NC region, the community structure of the FC material differed mainly in an increased abundance of B+G relative to that of ALF. The microcosm communities were like those of the field samples in that they were predominantly Bacteria (83 to 101%) and lacked detectable Archaea but differed in that a small fraction (2 to 8%) of Eucarya was detected regardless of the treatment applied. The latter result was hypothesized to reflect enrichment of anaerobic protozoa. Addition of nitrate and/or toluene stimulated microbial activity in the microcosms, but only supplementation of toluene alone significantly altered community structures. For the NC material, the dominant subclass shifted from B+G to ALF, while in the FC microcosms 55 to 65% of theBacteria community was no longer identifiable by the phylum or subclass probes used. The latter result suggested that toluene exposure fostered the proliferation of phylotype(s) that were otherwise minor constituents of the FC aquifer community. These studies demonstrated that alterations in aquifer microbial communities resulting from specific anthropogenic perturbances can be inferred from microcosm studies integrating chemical and phylogenetic probe analysis and in the case of hydrocarbon contamination may facilitate the identification of organisms important for in situ biodegradation processes. Further work integrating and coordinating microcosm and field experiments is needed to explore how differences in scale, substrate complexity, and other hydrogeological conditions may affect patterns observed in these systems.
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Anderson, Sally A., Christopher H. Sissons, Megan J. Coleman, and Lisa Wong. "Application of Carbon Source Utilization Patterns To Measure the Metabolic Similarity of Complex Dental Plaque Biofilm Microcosms." Applied and Environmental Microbiology 68, no. 11 (November 2002): 5779–83. http://dx.doi.org/10.1128/aem.68.11.5779-5783.2002.
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ABSTRACT Biolog technology was applied to measure the metabolic similarity of plaque biofilm microcosms, which model the complex properties of dental plaque in vivo. The choice of Biolog plate, incubation time, and incubation conditions strongly influenced utilization profiles. For plaque biofilm microcosms, Biolog GP2 plates incubated anaerobically in an H2-free atmosphere gave the clearest profile. To test the application of the Biolog GP2 assay, plaque microcosms were developed under different nutrient conditions in which the frequency of sucrose application was varied. Cluster analysis of Biolog GP2 data from 10 microcosm biofilms correlated with sucrose frequency. Aciduric bacteria (Streptococcus mutans plus lactobacilli) predominated in the plaques receiving high-frequency sucrose applications. Agreement between the Biolog GP2 groupings with nutrient and compositional changes suggests that Biolog analysis is a valuable technique for analyzing the metabolic similarity of dental plaque biofilm microcosms and other high-nutrient or predominantly anaerobic ecosystems.
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Janke, H., TM Yamada, DAS Beraldo, CMR Botta, MRL Nascimento, and AA Mozeto. "Assessment of the acute toxicity of eutrophic sediments after the addition of calcium nitrate (Ibirité reservoir, Minas Gerais-SE Brazil): initial laboratory experiments." Brazilian Journal of Biology 71, no. 4 (November 2011): 903–14. http://dx.doi.org/10.1590/s1519-69842011000500011.
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This study evaluated the acute toxicity of sediment in a eutrophic reservoir after remediation with a calcium nitrate solution to retain phosphorus. The study involved microcosms of surface sediments and water from the sediment-water interface in the Ibirité reservoir. This reservoir, located in the vicinity of metropolitan Belo Horizonte (Minas Gerais, SE Brazil), is a water body that receives treated effluents from an oil refinery (REGAP-Petrobras), as well as high loads of untreated urban effluents from the city of Ibirité and surrounding areas and industrial effluents from a major industrial park. Incubation times of the treatment experiments were: t = 0, t = 5, t = 10, t = 25, t = 50, t = 85 and t = 135 days. One control microcosm and three treated microcosms were analysed in each time interval. Acute toxicity of water samples was assessed with Ceriodaphnia silvestrii Daday, 1902 and that of bulk sediment samples with Chironomus xanthus Rempel, 1939. Toxicity tests were carried out concomitantly with chemical analyses of dissolved inorganic nitrogen species (ammonia, nitrate and nitrite), sulfate and metals in the water samples of the microcosms. Acid volatile sulfides (AVS), simultaneously extracted metal (SEM) and potentially bioavailable metal were analyzed in bulk sediment samples. Neither of the tested organisms showed toxicity in the control microcosm samples. The water column of the treated microcosm showed toxicity to C. silvestrii, starting at t = 10 days, while the sediment pore water toxicity started at t = 0 day. However, toxicity was found to decline from t = 85 days to t = 135 days. Sediments showed toxicity to C. xanthus during the entire experiment, except at the longest incubation time (t = 135 days). The overall results indicate that nitrate, which reached concentrations exceeding 1,200 mg N-NO3- L-1 in the sediment pore water of the treated microcosms, was most probably responsible for the toxicity of the samples. Although the calcium nitrate technology proved effective in retaining phosphorus, promoting sediment oxidation via denitrification, from the ecotoxicological standpoint and under the experimental conditions of this study, the application of nitrate for remediation of the sediments in the Ibirité reservoir did not prove effective up to a period of 135 days of incubation. However, we presume that after longer periods of incubation, treated sediments may recover their ability to sustain a benthic community. More advanced experiments are planned involving longer incubation times, thus extending the denitrification process, which may lead to a higher phosphorus retention capacity and to more complete abatement of sediment toxicity.
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McBain, Andrew J., Robert G. Bartolo, Carl E. Catrenich, Duane Charbonneau, Ruth G. Ledder, and Peter Gilbert. "Effects of Triclosan-Containing Rinse on the Dynamics and Antimicrobial Susceptibility of In Vitro Plaque Ecosystems." Antimicrobial Agents and Chemotherapy 47, no. 11 (November 2003): 3531–38. http://dx.doi.org/10.1128/aac.47.11.3531-3538.2003.
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ABSTRACT Dental plaque microcosms were established under a feast-famine regimen within constant-depth film fermentors and exposed four times daily postfeeding to a triclosan (TR)-containing rinse (dentifrice) (TRD). This was diluted so that the antimicrobial content was 0.6 mg/ml. Microcosms were characterized by heterotrophic plate counts and PCR-denaturing gradient gel electrophoresis (DGGE) with primers specific for the V2-V3 region of the eubacterial 16S rRNA gene (rDNA). Dominant isolates and PCR amplicons were identified by partial sequencing of 16S rDNA. TRD caused considerable decreases in the counts of both gram-negative organisms and total anaerobic cells, transiently lowered the numbers of streptococci and actinomycetes, and markedly increased the proportion of lactobacilli. DGGE indicated the presence of putatively unculturable bacteria and showed that a Porphyromonas sp. and Selenomonas infelix had been inhibited by TRD. Pure culture studies of 10 oral bacteria (eight genera) showed that Neisseria subflava, Prevotella nigrescens, and Porphyromonas gingivalis were highly susceptible to TR, while the lactobacilli and streptococci were the least susceptible. Clonal expansion of the lactobacilli in the pulsed microcosm could be explained on the basis of TR activity. The mean MICs of TR, chlorhexidine, erythromycin, penicillin V, and vancomycin for the population before and after 5 days of exposure to TRD showed few significant changes. In conclusion, changes in plaque microcosm populations following repeated exposure to TRD showed inhibition of the most susceptible flora and clonal expansion of less susceptible species.
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Zatsarnaya, N. A. "Microcosm of Ecologic Taxation in Russia." Vestnik of the Plekhanov Russian University of Economics, no. 1 (February 14, 2022): 42–54. http://dx.doi.org/10.21686/2413-2829-2022-1-42-54.
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The article analyzes wordings of the category ‘ecosystem’ as a form of interaction in economics. Drawbacks of the current definitions of the term were identified and the wording of the category ‘ecosystem’, which is the most substantiated for the present research, was presented. The term ‘microcosm of ecologic taxation’ was introduced and defined. Common features and differences, the structure, elements and the internal set-up of the ecosystem and microcosm were described. The author underlined the strategic importance of the ecosystem approach in view of possible evolution of the ecosystem (microcosm) value (principle idea) in conditions of instability, the place of microcosm of ecologic taxation was identified in the economic system of Russia. The key part in microcosm being studied is assigned not to economic entities and administrative agents but to the network of interrelations, tools and control levers integrating them. The forms of its actors’ interaction are shown, i. e. persons united by their involvement in ecologic tax payment (beneficiaries, tax payers and bearers). The idea and definition of the cluster as an association underlying microcosm were given. The cluster was shown as a complicated association of simple entities of economic relations, working in similar social-demographic, climatic and natural-resource conditions. The cluster structure was depicted as an element of the structure of ecologic taxation microcosm. The article substantiated the possibility to use microcosm of ecologic taxation as a management tool aimed at providing ecologic security of the country.
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LeJeune, Jeffrey T., Thomas E. Besser, and Dale D. Hancock. "Cattle Water Troughs as Reservoirs ofEscherichia coli O157." Applied and Environmental Microbiology 67, no. 7 (July 1, 2001): 3053–57. http://dx.doi.org/10.1128/aem.67.7.3053-3057.2001.
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ABSTRACT Environmental survival of Escherichia coli O157 may play an important role in the persistence and dissemination of this organism on farms. The survival of culturable and infectious E. coli O157 was studied using microcosms simulating cattle water troughs. Culturable E. coli O157 survived for at least 245 days in the microcosm sediments. Furthermore, E. coli O157 strains surviving more than 6 months in contaminated microcosms were infectious to a group of 10-week-old calves. Fecal excretion ofE. coli O157 by these calves persisted for 87 days after challenge. Water trough sediments contaminated with feces from cattle excreting E. coli O157 may serve as a long-term reservoir of this organism on farms and a source of infection for cattle.
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Li, Fangru, Shang Wang, Qing He, Wenhui Zhang, Dongyi Guo, Yidi Zhang, Wanming Hai, Yuxuan Sun, Hailiang Dong, and Weiguo Hou. "Minerals Determined a Special Ecological Niche and Selectively Enriched Microbial Species from Bulk Water Communities in Hot Springs." Microorganisms 9, no. 5 (May 10, 2021): 1020. http://dx.doi.org/10.3390/microorganisms9051020.
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Minerals provide physical niches and supply nutrients or serve as electron donors/acceptors for microorganism survival and growth, and thus minerals and microbes co-evolved. Yet, little is known about how sediment minerals impact microbial community assembly in hot springs and to what extent mineralogical composition influences microbial community composition and diversity. Here the influences of minerals on thermophiles in Tengchong hot springs were revealed by network analysis of field samples, as well as in-situ microcosm experiments with minerals. A molecular ecological network was constructed based on high throughput sequencing data of 16S rRNA gene, with a combination of water geochemistry and sedimentary mineralogical compositions. Six modules were identified and this highly modular network structure represents the microbial preference to different abiotic factors, consequently resulting in niche partitioning in sedimentary communities in hot springs. Diverse mineralogical compositions generated special niches for microbial species. Subsequently, the in-situ microcosm experiments with four minerals (aragonite, albite, K-feldspar, and quartz) and spring water were conducted in a silicate-hosted alkaline spring (i.e., Gmq) and a carbonate-hosted neutral hot spring (i.e., Gxs) for 70 days. Different microbial preferences were observed among different mineral types (carbonate versus silicate). Aragonite microcosms in Gmq spring enriched archaeal genera Sulfophobococcus and Aeropyrum within the order Desulfurococcales by comparison with both in-situ water and silicate microcosms. Sulfophobococcus was also accumulated in Gxs aragonite microcosms, but the contribution to overall dissimilarity is much lower than that in Gmq spring. Besides, Caldimicrobium was a bacterial genus enriched in Gxs aragonite microcosms, in contrast to in-situ water and silicate microcosms, whereas Candidatus Kryptobacter and Thermus were more abundant in silicate microcosms. The differences in microbial accumulations among different mineral types in the same spring implied that mineral chemistry may exert extra deterministic selective pressure in drawing certain species from the bulk water communities, in addition to stochastic absorption on mineral surface. Taken together, our results highlight the special niche partitioning determined by mineralogical compositions and further confirm that minerals could be used as “fishing bait” to enrich certain rare microbial species.
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Rand, Gary M., James R. Clark, and Catherine M. Holmes. "USE of outdoor freshwater pond microcosms: I. Microcosm design and fate of pyridaben." Environmental Toxicology and Chemistry 19, no. 2 (February 2000): 387–95. http://dx.doi.org/10.1002/etc.5620190219.
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Hornsby, D. C., B. G. Lockaby, and A. H. Chappelka. "Influence of microclimate on decomposition in loblolly pine stands: a field microcosm approach." Canadian Journal of Forest Research 25, no. 10 (October 1, 1995): 1570–77. http://dx.doi.org/10.1139/x95-171.
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The effect of climatic variation on decomposition was studied in a field experiment. Plexiglas microcosms were used to elevate temperatures and allow implementation of varied precipitation rates. The study was conducted in a loblolly pine (Pinustaeda L.) stand near Auburn, Alabama. Temperatures were elevated (1–8 °C depending on the season) and precipitation was varied (±30% of ambient). A litterbag approach was used to examine decomposition dynamics within the microcosms. Elevated temperatures significantly increased decomposition rates within microcosm treatments. Enhanced moisture stimulated decomposition above that associated with ambient levels of precipitation while decreased precipitation produced no significant decrease in decomposition within our temperature range. In general, litter N concentrations increased, carbon content decreased, and C/N ratios decreased over time, and these effects were accelerated when temperature was increased. Within our range of environmental factors, increases in temperature could result in accelerated decomposition and alterations in nutrient cycling regardless of the precipitation change. However, should precipitation increase as well, litter decomposition will be further stimulated.
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KURIHARA, Yasushi. "Stability in ecological microcosm." Proceedings of the Japan Academy, Series B 80, no. 7 (2004): 327–35. http://dx.doi.org/10.2183/pjab.80.327.
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Wemmer, Chris. "The elephant-wallahs' microcosm." Elephant 2, no. 4 (January 1, 2000): 55–60. http://dx.doi.org/10.22237/elephant/1521732231.
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McArthur, Tom. "A microcosm of English." English Today 11, no. 1 (January 1995): 2. http://dx.doi.org/10.1017/s0266078400007987.
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Ramsey, Matthew. "A microcosm of society." Nature 410, no. 6826 (March 2001): 303–4. http://dx.doi.org/10.1038/35066623.
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Marchiò, Caterina, Francesca Pietribiasi, Roberta Castiglione, Nicola Fusco, and Anna Sapino. "“Giants in a Microcosm”." International Journal of Surgical Pathology 23, no. 8 (September 13, 2015): 654–55. http://dx.doi.org/10.1177/1066896915605616.
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Cornejo, Carlos. "Searching for the microcosm." History of the Human Sciences 28, no. 2 (April 2015): 72–92. http://dx.doi.org/10.1177/0952695114563842.
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Kaldis, Byron. "The University as Microcosm." Educational Philosophy and Theory 41, no. 5 (January 2009): 553–74. http://dx.doi.org/10.1111/j.1469-5812.2008.00431.x.
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McCaffery, Peter. "Catholic Newcastle as Microcosm." New Blackfriars 68, no. 802 (February 1987): 80–89. http://dx.doi.org/10.1111/j.1741-2005.1987.tb01227.x.
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Donnelly, Warren H. "Microcosm of energy policy." Energy Policy 17, no. 2 (April 1989): 139–40. http://dx.doi.org/10.1016/0301-4215(89)90094-3.
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Margulis, Lynn. "From Gaia to microcosm." Biosystems 31, no. 2-3 (January 1993): 83. http://dx.doi.org/10.1016/0303-2647(93)90034-a.
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Robichaud, AnnMarie. "A microcosm for learning." Journal of Professional Nursing 8, no. 6 (November 1992): 320. http://dx.doi.org/10.1016/8755-7223(92)90093-e.
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Astolfi, Stefania, Sabrina Zuchi, Fabrizio De Cesare, Luigi Badalucco, and Stefano Grego. "Cadmium-induced changes in soil biochemical characteristics of oat (Avena sativa L.) rhizosphere during early growth stages." Soil Research 49, no. 7 (2011): 642. http://dx.doi.org/10.1071/sr11158.
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A microcosm was assembled to physically separate soil from roots and was used to study both the impact of living roots on the soil–plant system during early stages of growth and plant responses to abiotic stress. Oat (Avena sativa L.) seedlings were grown in the microcosm unit for 44 days. Twenty-three days after planting, 0.154 mg CdSO4/g dry soil was added. Plants grown in Cd-treated microcosms showed considerable inhibition of shoot growth rates, and leaf chlorophyll content. Soil microbial biomass C and respiration increased with plant age, and most of the measured biochemical indicators decreased with increasing distance from the soil–root interface, thus demonstrating the rhizosphere effect, likely due to the quick assimilation of rhizodeposits by rhizosphere microflora. On the other hand, short-term Cd contamination sometimes had an inhibitory effect on soil respiration, qCO2, ATP content, and phosphatase activity, while stimulating microbial biomass, mainly at the rhizosphere level. The decrease in rhizosphere microbial activity observed after Cd application to soil may be due to a synergic effect of the metal directly on microbial cells and indirectly on plants, which reduced shoot growth rate and chlorophyll content, resulting in decreased availability of root exudates.
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McBain, Andrew J., Ruth G. Ledder, Louise E. Moore, Carl E. Catrenich, and Peter Gilbert. "Effects of Quaternary-Ammonium-Based Formulations on Bacterial Community Dynamics and Antimicrobial Susceptibility." Applied and Environmental Microbiology 70, no. 6 (June 2004): 3449–56. http://dx.doi.org/10.1128/aem.70.6.3449-3456.2004.
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ABSTRACT Quaternary ammonium compounds (QACs) are widely used as adjuncts to hygiene in domestic cleaning products. Current concern that the increased use of such biocides in consumer products might contribute to the emergence of antibiotic resistance has led us to examine the effects of a QAC-containing domestic cleaning fluid on the population dynamics and antimicrobial susceptibility of domestic sink drain biofilm communities. QAC susceptibilities of numerically dominant, culturable drain bacteria (15 genera, 17 species) were determined in vitro before and after repeated QAC exposure (14 passages). A fully characterized drain microcosm was then exposed to short-term (12 days) and long-term (3 months) dosing with a QAC-containing domestic detergent (QD). QAC exposure of isolated cultures caused both increases (three species) and circa twofold decreases (six species) in QAC susceptibility. The susceptibility of Ralstonia sp. was considerably decreased following 14 consecutive QAC passages. Control drain microcosm biofilms maintained dynamic stability, as evidenced by culture and denaturing gradient gel electrophoresis (DGGE) analysis. Bacterial population densities were largely unaffected during short-term exposure to use levels of QD, although 50% QD caused circa 10-fold viability reductions. DGGE analysis supported these observations; identified the major microcosm genera as Pseudomonas, Pseudoalteromonas, Erwinia, and Enterobacter, and showed that aeromonads increased in abundance under 10 to 50% QD. Long-term exposure of the microcosms to QD did not significantly alter the pattern of antimicrobial susceptibility. These data demonstrate the recalcitrance of domestic drain biofilms toward QAC and that although repeated QAC exposure of drain isolates in pure culture results in susceptibility change in some test bacteria, such changes do not necessarily occur within complex communities.