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Regin Rønn - One of the best experts on this subject based on the ideXlab platform.

  • a role for copper in Protozoan grazing two billion years selecting for bacterial copper resistance
    Molecular Microbiology, 2016
    Co-Authors: Xiuli Hao, Regin Rønn, Freja Lea Luthje, Nadezhda German, Fuyi Huang, Javan Kisaka, David L Huffman, Hend A Alwathnani, Yongguan Zhu, Christopher Rensing
    Abstract:

    The Great Oxidation Event resulted in integration of soft metals in a wide range of biochemical processes including, in our opinion, killing of bacteria by protozoa. Compared to pressure from anthropologic copper contamination, little is known on impacts of Protozoan predation on maintenance of copper resistance determinants in bacteria. To evaluate the role of copper and other soft metals in predatory mechanisms of protozoa, we examined survival of bacteria mutated in different transition metal efflux or uptake systems in the social amoeba Dictyostelium discoideum. Our data demonstrated a strong correlation between the presence of copper/zinc efflux as well as iron/manganese uptake, and bacterial survival in amoebae. The growth of protozoa, in turn, was dependent on bacterial copper sensitivity. The phagocytosis of bacteria induced upregulation of Dictyostelium genes encoding the copper uptake transporter p80 and a triad of Cu(I)-translocating PIB -type ATPases. Accumulated Cu(I) in Dictyostelium was monitored using a copper biosensor bacterial strain. Altogether, our data demonstrate that Cu(I) is ultimately involved in Protozoan predation of bacteria, supporting our hypothesis that Protozoan grazing selected for the presence of copper resistance determinants for about two billion years.

  • Response of free-living soil protozoa and microorganisms to elevated atmospheric CO2 and presence of mycorrhiza
    Soil Biology and Biochemistry, 2002
    Co-Authors: Regin Rønn, Mayra E. Gavito, John Larsen, Iver Jakobsen, Helle B. Frederiksen, Soren Christensen
    Abstract:

    Abstract Possible interactions between mycorrhiza, atmospheric CO 2 , free-living soil microorganisms and protozoa were investigated in pot experimental systems. Pea plants ( Pisum sativum L. cv. Solara) were grown under ambient (360 μl l −1 ) or elevated (700 μl l −1 ) atmospheric CO 2 concentration with or without the presence of the arbuscular mycorrhizal (AM) fungus Glomus caledonium . It was hypothesised that (1) the populations of free-living soil protozoa would increase as a response to elevated CO 2 , (2) the effect of elevated CO 2 on protozoa would be moderated by the presence of mycorrhiza and (3) the presence of arbuscular mycorrhiza would affect soil Protozoan numbers regardless of atmospheric CO 2 . After 3 weeks growth there was no difference in bacterial numbers (direct counts) in soil, but the number of free-living bacterial-feeding protozoa was significantly higher under elevated CO 2 and was significantly reduced in the mycorrhizal treatments. These effects on protozoa disappeared after 5 and 9 weeks. Neither mycorrhiza nor CO 2 concentration had any substantial effect on the microbial community structure as evaluated by phospholipid fatty acid analysis. The increased Protozoan populations under elevated CO 2 suggest increased bacterial production, whereas the lower populations in response to presence of mycorrhiza suggest a depressing effect on bacterial production by AM colonisation.

  • Impact of Protozoan Grazing on Bacterial Community Structure in Soil Microcosms
    Applied and environmental microbiology, 2002
    Co-Authors: Regin Rønn, Bryan S. Griffiths, A. E. Mccaig, James I. Prosser
    Abstract:

    The influence of grazing by a mixed assemblage of soil protozoa (seven flagellates and one amoeba) on bacterial community structure was studied in soil microcosms amended with a particulate resource (sterile wheat roots) or a soluble resource (a solution of various organic compounds). Sterilized soil was reinoculated with mixed soil bacteria (obtained by filtering and dilution) or with bacteria and protozoa. Denaturing gradient gel electrophoresis (DGGE) of PCR amplifications of 16S rRNA gene fragments, as well as community level physiological profiling (Biolog plates), suggested that the mixed Protozoan community had significant effects on the bacterial community structure. Excising and sequencing of bands from the DGGE gels indicated that high-G+C gram-positive bacteria closely related to Arthrobacter spp. were favored by grazing, whereas the excised bands that decreased in intensity were related to gram-negative bacteria. The percentages of intensity found in bands related to high G+C gram positives increased from 4.5 and 12.6% in the ungrazed microcosms amended with roots and nutrient solution, respectively, to 19.3 and 32.9% in the grazed microcosms. Protozoa reduced the average bacterial cell size in microcosms amended with nutrient solution but not in the treatment amended with roots. Hence, size-selective feeding may explain some but not all of the changes in bacterial community structure. Five different Protozoan isolates (Acanthamoeba sp., two species of Cercomonas, Thaumatomonas sp., and Spumella sp.) had different effects on the bacterial communities. This suggests that the composition of Protozoan communities is important for the effect of Protozoan grazing on bacterial communities.

  • distribution with depth of protozoa bacteria and fungi in soil profiles from three danish forest sites
    Soil Biology & Biochemistry, 2001
    Co-Authors: Flemming Ekelund, Regin Rønn, Soren Christensen
    Abstract:

    Abstract The numbers and biomass of protozoa, bacteria and fungi were measured at various depths (1.5–122.5 cm) in the unsaturated zone of three contrasting pristine Danish forest site profiles: a dry beech (Fagus silvatica) forest on mor, a wet peaty spruce (Picea abies)/birch (Betula pubescens) forest and a dry spruce (P. abies) forest on mor. All sites were situated on a Weichel moraine. Except for a bacterial peak at 42.5 cm in the peat profile, the general tendency was a decrease in biomass with increasing depth for all groups examined. Protozoa decreased more rapidly with increasing depth than the other two groups of organisms examined. An evaluation of the bacterial–Protozoan relationship by a simple mathematical model indicated that the subsurface Protozoan populations are active and not accidental percolated cysts. The low Protozoan numbers found in shallow subsurface sites contrast markedly with the results from contaminated sites where much larger Protozoan populations have been reported even at considerable depths. Consequently, the results suggest that protozoa are good indicators of organic pollution in subsurface soils; however, more work involving the comparison of polluted and unpolluted soils is needed to confirm this suggestion.

  • Protozoan response to addition of the bacteria Mycobacterium chlorophenolicum and Pseudomonas chlororaphis to soil microcosms
    Biology and Fertility of Soils, 2001
    Co-Authors: Regin Rønn, J. Grunert, Fleming Ekelund
    Abstract:

    Protozoa are important predators of bacteria in soil and Protozoan predation is one of the main factors responsible for the decline of bacterial populations introduced into soil. Bacteria, however, are not equally susceptible to Protozoan predation. We have studied the response of indigenous Protozoan populations to the introduction of the polychlorophenol-degrading bacterium Mycobacterium chlorophenolicum PCP-1 (DSM 43826), and Pseudomonas chlororaphis (ATCC 43928), into soil microcosms. Introduction of P. chlororaphis to the soil resulted in a huge increase in the numbers of heterotrophic flagellates and naked amoebae during the first 8 days of the experiment. Addition of M. chlorophenolicum to soil caused only a slight increase in Protozoan numbers, which was similar to the increase caused by addition of water. There was no indication that addition of M. chlorophenolicum to soil resulted in any increase in the number of protozoa able to feed on this bacterium. The number of colony forming units (CFU) decreased rapidly in the treatment amended with P. chlororaphis cells, whereas there was no decrease in CFUs in the M. chlorophenolicum treatment. The only slight increase in Protozoan numbers in the M. chlorophenolicum treatment, as well as the apparently low mortality rate of M. chlorophenolicum in the soil microcosms, coincided with significantly lower soil respiration in the soil microcosms amended with M. chlorophenolicum compared to those amended with P. chlororaphis. The results suggest that the indigenous soil protozoa did not graze on M. chlorophenolicum at all, presumably because it is not a suitable food source.

J. M. Pemberton - One of the best experts on this subject based on the ideXlab platform.

  • epidemiology of parasitic Protozoan infections in soay sheep ovis aries l on st kilda
    Parasitology, 2007
    Co-Authors: B. H. Craig, J. G. Pilkington, L. E. B. Kruuk, J. M. Pemberton
    Abstract:

    The feral Soay sheep (Ovis aries L.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the Protozoan species comprising Cryptosporidium parvum, Giardia duodenalis and 11 species of Eimeria in Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception of E. granulosa, which increased in prevalence with host age. The prevalence of C. parvum appeared to vary positively with host population density but that of G. duodenalis did not vary significantly with density. Most species of Eimeria showed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. Mixed Eimeria species intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.

  • Epidemiology of parasitic Protozoan infections in Soay sheep (Ovis ariesL.) on St Kilda
    Parasitology, 2006
    Co-Authors: B. H. Craig, J. G. Pilkington, L. E. B. Kruuk, J. M. Pemberton
    Abstract:

    The feral Soay sheep (Ovis ariesL.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the Protozoan species comprisingCryptosporidium parvum,Giardia duodenalisand 11 species ofEimeriain Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception ofE. granulosa, which increased in prevalence with host age. The prevalence ofC. parvumappeared to vary positively with host population density but that ofG. duodenalisdid not vary significantly with density. Most species ofEimeriashowed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. MixedEimeriaspecies intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.

B. H. Craig - One of the best experts on this subject based on the ideXlab platform.

  • epidemiology of parasitic Protozoan infections in soay sheep ovis aries l on st kilda
    Parasitology, 2007
    Co-Authors: B. H. Craig, J. G. Pilkington, L. E. B. Kruuk, J. M. Pemberton
    Abstract:

    The feral Soay sheep (Ovis aries L.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the Protozoan species comprising Cryptosporidium parvum, Giardia duodenalis and 11 species of Eimeria in Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception of E. granulosa, which increased in prevalence with host age. The prevalence of C. parvum appeared to vary positively with host population density but that of G. duodenalis did not vary significantly with density. Most species of Eimeria showed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. Mixed Eimeria species intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.

  • Epidemiology of parasitic Protozoan infections in Soay sheep (Ovis ariesL.) on St Kilda
    Parasitology, 2006
    Co-Authors: B. H. Craig, J. G. Pilkington, L. E. B. Kruuk, J. M. Pemberton
    Abstract:

    The feral Soay sheep (Ovis ariesL.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the Protozoan species comprisingCryptosporidium parvum,Giardia duodenalisand 11 species ofEimeriain Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception ofE. granulosa, which increased in prevalence with host age. The prevalence ofC. parvumappeared to vary positively with host population density but that ofG. duodenalisdid not vary significantly with density. Most species ofEimeriashowed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. MixedEimeriaspecies intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.

L. E. B. Kruuk - One of the best experts on this subject based on the ideXlab platform.

  • epidemiology of parasitic Protozoan infections in soay sheep ovis aries l on st kilda
    Parasitology, 2007
    Co-Authors: B. H. Craig, J. G. Pilkington, L. E. B. Kruuk, J. M. Pemberton
    Abstract:

    The feral Soay sheep (Ovis aries L.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the Protozoan species comprising Cryptosporidium parvum, Giardia duodenalis and 11 species of Eimeria in Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception of E. granulosa, which increased in prevalence with host age. The prevalence of C. parvum appeared to vary positively with host population density but that of G. duodenalis did not vary significantly with density. Most species of Eimeria showed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. Mixed Eimeria species intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.

  • Epidemiology of parasitic Protozoan infections in Soay sheep (Ovis ariesL.) on St Kilda
    Parasitology, 2006
    Co-Authors: B. H. Craig, J. G. Pilkington, L. E. B. Kruuk, J. M. Pemberton
    Abstract:

    The feral Soay sheep (Ovis ariesL.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the Protozoan species comprisingCryptosporidium parvum,Giardia duodenalisand 11 species ofEimeriain Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception ofE. granulosa, which increased in prevalence with host age. The prevalence ofC. parvumappeared to vary positively with host population density but that ofG. duodenalisdid not vary significantly with density. Most species ofEimeriashowed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. MixedEimeriaspecies intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.

J. G. Pilkington - One of the best experts on this subject based on the ideXlab platform.

  • epidemiology of parasitic Protozoan infections in soay sheep ovis aries l on st kilda
    Parasitology, 2007
    Co-Authors: B. H. Craig, J. G. Pilkington, L. E. B. Kruuk, J. M. Pemberton
    Abstract:

    The feral Soay sheep (Ovis aries L.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the Protozoan species comprising Cryptosporidium parvum, Giardia duodenalis and 11 species of Eimeria in Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception of E. granulosa, which increased in prevalence with host age. The prevalence of C. parvum appeared to vary positively with host population density but that of G. duodenalis did not vary significantly with density. Most species of Eimeria showed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. Mixed Eimeria species intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.

  • Epidemiology of parasitic Protozoan infections in Soay sheep (Ovis ariesL.) on St Kilda
    Parasitology, 2006
    Co-Authors: B. H. Craig, J. G. Pilkington, L. E. B. Kruuk, J. M. Pemberton
    Abstract:

    The feral Soay sheep (Ovis ariesL.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the Protozoan species comprisingCryptosporidium parvum,Giardia duodenalisand 11 species ofEimeriain Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception ofE. granulosa, which increased in prevalence with host age. The prevalence ofC. parvumappeared to vary positively with host population density but that ofG. duodenalisdid not vary significantly with density. Most species ofEimeriashowed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. MixedEimeriaspecies intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.