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Tom Fenchel - One of the best experts on this subject based on the ideXlab platform.
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what is a Protozoon
2020Co-Authors: Genoveva F. Esteban, Tom FenchelAbstract:The question as stated by the chapter heading is not trivial. Many standard textbooks define protozoa as “unicellular animals”, but this is not satisfactory. The idea that protozoa are unicellular in the sense that they correspond to a single cell of a multicellular organism was first conceived about 200 years after their discovery by Leeuwenhoek in 1674. The term “Protozoa” was coined by Goldfuss in 1817 to mean “original animals” and he included the coelenterates.
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an anaerobic Protozoon with symbiotic methanogens living in municipal landfill material
Fems Microbiology Letters, 1991Co-Authors: Bland J. Finlay, Tom FenchelAbstract:We have established that anaerobic protozoa do live in municipal landfill material although they probably spend much of the time encysted, especially in the drier (< 40% water) site. At least eight species were observed; they were readily isolated by adding anoxic water to dry landfill samples. The ciliate Metopus palaeformis was frequently i isolated; it appears to be ubiquitous in anaerobic landfills. It has a polymorphic life cycle, it is positive for hydrogenase, each ciliate contains about 500 bromoethanesulfonate-sensitive methanogen symbionts (probably Methanobacterium formicicum), and maximum cell densities in culture exceed 3000 per ml. The methanogens are not attached to the hydrogenosomes, neither do they undergo morphological transformation; the ciliate receives no measurable energetic advantage from its symbionts. The ciliate encysts in response to a shortage of food or water, and the methanogens remain viable within the cysts. When the Protozoon excysts, the methanogens resume growth and cell division within the trophic form of the ciliate. Unlike free-living methanogens, the M. palaeformis-methanogen consortium is not particularly sensitive to oxygen; the symbiotic methanogens remain viable following exposure of the consortium to atmospheric oxygen for several days. Dispersal of methanogen-bearing protozoan cysts through oxygenated environments is a potential mechanism of transfer between landfill sites and other anaerobic environments. Anaerobic protozoan consortia are theoretically capable of making a significant contribution to methane generation from wet landfill sites.
Aaron L. Mills - One of the best experts on this subject based on the ideXlab platform.
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impact of water column acidification on protozoan bacterivory at the lake sediment water interface
Applied and Environmental Microbiology, 1991Co-Authors: Sarah C. Tremaine, Aaron L. MillsAbstract:Although the impact of acidification on planktonic grazer food webs has been extensively studied, little is known about microbial food webs either in the water column or in the sediments. Protozoan-bacterium interactions were investigated in a chronically acidified (acid mine drainage) portion of a lake in Virginia. The authors determined the distribution, abundance, apparent specific grazing rate, and growth rate of protozoa over a pH range of 3.6 to 6.5. Protozoan abundance was lower at the most acidified site, while abundance, in general, was high compared with other systems. Specific grazing rates were uncorrelated with pH and ranged between 0.02 and 0.23 h{sup {minus}1}, values similar to those in unacidified systems. The protozoan community from an acidified station was not better adapted to low-pH conditions than a community from an unacidified site (multivariate analysis of variance on growth rates for each community incubated at pHs 4, 5, and 6). Both communities had significantly lower growth rates at pHs 4 and 5 than at pH 6. Reduced protozoan growth rates coupled with high grazing rates and relatively higher bacterial yields (ratio of bacterial-protozoan standing stock) at low pH indicate reduced net protozoan growth efficiency and a metabolic cost of acidification tomore » the protozoan community. However, the presence of an abundant, neutrophilic protozoan community and high bacterial grazing rates indicates that acidification of Lake Anna has not inhibited the bacterium-protozoan link of the sediment microbial food web.« less
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ImpactofWaterColumnAcidification on Protozoan Bacterivory at theLakeSediment-Water Interface
1991Co-Authors: Sarah C. Tremaine, Aaron L. MillsAbstract:Although theimpact ofacidification on planktonic grazer foodwebshasbeenextensively studied, little is knownaboutmicrobial foodwebseither inthewatercolumnor inthesediments. Protozoon-bacterium interactions were investigated ina chronically acidified (acid minedrainage) portion ofa lakeinVirginia. We determined thedistribution, abundance, apparent specific grazing rate,andgrowth rateofprotozoa over a pH rangeof3.6to6.5. Protozoan abundance was lower atthemostacidified site, while abundance, ingeneral, was highcompared withother systems. Specific grazing rates were uncorrelated withpH andrangedbetween0.02 and0.23h-1,values similar tothose inunacidified systems. Theprotozoan community froman acidified station was notbetter adapted (P= 0.95) tolow-pHconditions thanacommunity froman unacidified site (multivariate analysis ofvariance on growth rates foreachcommunity incubated atpHs4,5,and6).Bothcommunities had significantly lower(P< 0.05) growthratesatpHs4and5thanatpH 6.Reducedprotozoan growthrates coupled withhighgrazing ratesandrelatively higher bacterial yields (ratio ofbacterial-protozoan standing stock) atlowpHindicate reduced netprotozoan growthefficiency anda metabolic costofacidification tothe protozoan community. However, thepresenceofan abundant, neutrophilic protozoan community andhigh bacterial grazing rates indicates that acidification ofLakeAnnahasnotinhibited thebacterium-Protozoon link
Bland J. Finlay - One of the best experts on this subject based on the ideXlab platform.
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soil protozoa an intensive study of population dynamics and community structure in an upland grassland
Applied Soil Ecology, 2006Co-Authors: Genoveva F. Esteban, Ken J. Clarke, José L. Olmo, Bland J. FinlayAbstract:We focus on the key results from a 3-year intensive investigation of soil protozoan diversity sponsored by the Natural Environment Research Council (UK). The investigation enabled us to study simultaneously all major protozoan groups at a single site—the 1 ha area of upland grassland at the Macaulay Land Use Research Institute’s Sourhope Research Station in Southern Scotland. A total of 365 protozoan species were recorded, in four broad taxonomic groups—ciliates, testate amoebae, naked amoebae and flagellates. We explored the natural history of these groups, recording species richness, growth rates, and absolute abundance, as well as community structures within the context of the fractal character of the soil. We developed methods for estimating the abundance and growth potential of the soil protozoan community, plus seasonal variation in protozoan abundance within taxonomic groups. We isolated new species, re-described others, and produced a guide to the identification of testate amoebae in soil. We produced evidence for the ubiquitous random dispersal of soil protozoa, and we found no evidence for geographically restricted distributions at spatial scales ranging from 4 m 2 to global. Roughly one quarter of global free-living protozoan diversity was recorded from this 1 ha site. Local and global abundances were correlated—i.e. species that are locally rare tend to be globally rare, and those that are locally abundant tend to be globally abundant. # 2006 Elsevier B.V. All rights reserved.
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an anaerobic Protozoon with symbiotic methanogens living in municipal landfill material
Fems Microbiology Letters, 1991Co-Authors: Bland J. Finlay, Tom FenchelAbstract:We have established that anaerobic protozoa do live in municipal landfill material although they probably spend much of the time encysted, especially in the drier (< 40% water) site. At least eight species were observed; they were readily isolated by adding anoxic water to dry landfill samples. The ciliate Metopus palaeformis was frequently i isolated; it appears to be ubiquitous in anaerobic landfills. It has a polymorphic life cycle, it is positive for hydrogenase, each ciliate contains about 500 bromoethanesulfonate-sensitive methanogen symbionts (probably Methanobacterium formicicum), and maximum cell densities in culture exceed 3000 per ml. The methanogens are not attached to the hydrogenosomes, neither do they undergo morphological transformation; the ciliate receives no measurable energetic advantage from its symbionts. The ciliate encysts in response to a shortage of food or water, and the methanogens remain viable within the cysts. When the Protozoon excysts, the methanogens resume growth and cell division within the trophic form of the ciliate. Unlike free-living methanogens, the M. palaeformis-methanogen consortium is not particularly sensitive to oxygen; the symbiotic methanogens remain viable following exposure of the consortium to atmospheric oxygen for several days. Dispersal of methanogen-bearing protozoan cysts through oxygenated environments is a potential mechanism of transfer between landfill sites and other anaerobic environments. Anaerobic protozoan consortia are theoretically capable of making a significant contribution to methane generation from wet landfill sites.
Sarah C. Tremaine - One of the best experts on this subject based on the ideXlab platform.
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impact of water column acidification on protozoan bacterivory at the lake sediment water interface
Applied and Environmental Microbiology, 1991Co-Authors: Sarah C. Tremaine, Aaron L. MillsAbstract:Although the impact of acidification on planktonic grazer food webs has been extensively studied, little is known about microbial food webs either in the water column or in the sediments. Protozoan-bacterium interactions were investigated in a chronically acidified (acid mine drainage) portion of a lake in Virginia. The authors determined the distribution, abundance, apparent specific grazing rate, and growth rate of protozoa over a pH range of 3.6 to 6.5. Protozoan abundance was lower at the most acidified site, while abundance, in general, was high compared with other systems. Specific grazing rates were uncorrelated with pH and ranged between 0.02 and 0.23 h{sup {minus}1}, values similar to those in unacidified systems. The protozoan community from an acidified station was not better adapted to low-pH conditions than a community from an unacidified site (multivariate analysis of variance on growth rates for each community incubated at pHs 4, 5, and 6). Both communities had significantly lower growth rates at pHs 4 and 5 than at pH 6. Reduced protozoan growth rates coupled with high grazing rates and relatively higher bacterial yields (ratio of bacterial-protozoan standing stock) at low pH indicate reduced net protozoan growth efficiency and a metabolic cost of acidification tomore » the protozoan community. However, the presence of an abundant, neutrophilic protozoan community and high bacterial grazing rates indicates that acidification of Lake Anna has not inhibited the bacterium-protozoan link of the sediment microbial food web.« less
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ImpactofWaterColumnAcidification on Protozoan Bacterivory at theLakeSediment-Water Interface
1991Co-Authors: Sarah C. Tremaine, Aaron L. MillsAbstract:Although theimpact ofacidification on planktonic grazer foodwebshasbeenextensively studied, little is knownaboutmicrobial foodwebseither inthewatercolumnor inthesediments. Protozoon-bacterium interactions were investigated ina chronically acidified (acid minedrainage) portion ofa lakeinVirginia. We determined thedistribution, abundance, apparent specific grazing rate,andgrowth rateofprotozoa over a pH rangeof3.6to6.5. Protozoan abundance was lower atthemostacidified site, while abundance, ingeneral, was highcompared withother systems. Specific grazing rates were uncorrelated withpH andrangedbetween0.02 and0.23h-1,values similar tothose inunacidified systems. Theprotozoan community froman acidified station was notbetter adapted (P= 0.95) tolow-pHconditions thanacommunity froman unacidified site (multivariate analysis ofvariance on growth rates foreachcommunity incubated atpHs4,5,and6).Bothcommunities had significantly lower(P< 0.05) growthratesatpHs4and5thanatpH 6.Reducedprotozoan growthrates coupled withhighgrazing ratesandrelatively higher bacterial yields (ratio ofbacterial-protozoan standing stock) atlowpHindicate reduced netprotozoan growthefficiency anda metabolic costofacidification tothe protozoan community. However, thepresenceofan abundant, neutrophilic protozoan community andhigh bacterial grazing rates indicates that acidification ofLakeAnnahasnotinhibited thebacterium-Protozoon link
A. Koutselinis - One of the best experts on this subject based on the ideXlab platform.
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phagocytosis of the Protozoon tetrahymena pyriformis as an endpoint in the estimation of cocaine salt and cocaine freebase toxicity
Addiction Biology, 1999Co-Authors: Maria Stefanidou, C. Maravelias, G Alevisopoulos, C Loutsidis, A. KoutselinisAbstract:Cells of the ciliated Protozoon Tetrahymena pyriformis strain W, grown in a peptone-yeast medium, usually contain many phagocytic vacuoles. The phagocytic activity of this Protozoon was studied in vivo using heat-inactivated yeast stained with carmine after exposing the cultures for 1 hour to different doses of cocaine hydrochloride or cocaine freebase (crack) (0.5, 1 or 2 mg/100 ml of protozoan culture).The number of vacuoles formed indicated the phagocytic activity. Cocaine hydrochloride and crack caused a decrease of the phagocytic activity of the Protozoon (p < 0.05) when compared to the control cultures. Furthermore, the two chemical forms of cocaine, salt and free-base respectively, caused quantitatively different effects on the phagocytic activity. Crack produced an extensive decrease in phagocytosis, compared to equal concentrations of cocaine hydrochloride. These results suggest a possible relationship between cocaine abuse and the suppression of phagocytosis that may contribute to the impairment of immunity in drug misusers.
