| 1. |
- Algesten, Grete, et al.
(författare)
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Contribution of sediment respiration to summer CO2 emission from boreal and subarctic lakes
- 2005
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 50:4, s. 529-535
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Tidskriftsartikel (refereegranskat)abstract
- We measured sediment production of carbon dioxide (CO(2)) and methane (CH(4)) and the net flux of CO(2) across the surfaces of 15 boreal and subarctic lakes of different humic contents. Sediment respiration measurements were made in situ under ambient light conditions. The flux of CO(2) between sediment and water varied between an uptake of 53 and an efflux of 182 mg C m(-2) day(-1) from the sediments. The mean respiration rate for sediments in contact with the upper mixed layer (SedR) was positively correlated to dissolved organic carbon (DOC) concentration in the water (r(2) = 0.61). The net flux of CO(2) across the lake surface [net ecosystem exchange (NEE)] was also closely correlated to DOC concentration in the upper mixed layer (r(2) = 0.73). The respiration in the water column was generally 10-fold higher per unit lake area compared to sediment respiration. Lakes with DOC concentrations <5.6 mg L(-1) had net consumption of CO(2) in the sediments, which we ascribe to benthic primary production. Only lakes with very low DOC concentrations were net autotrophic (<2.6 mg L(-1)) due to the dominance of dissolved allochthonous organic carbon in the water as an energy source for aquatic organisms. In addition to previous findings of allochthonous organic matter as an important driver of heterotrophic metabolism in the water column of lakes, this study suggests that sediment metabolism is also highly dependent on allochthonous carbon sources.
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| 2. |
- Algesten, Grete, et al.
(författare)
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Contribution of sediment respiration to summer CO2 emission from low productive boreal and subarctic lakes
- 2005
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 50:4, s. 529-535
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Tidskriftsartikel (refereegranskat)abstract
- We measured sediment production of carbon dioxide (CO2) and methane (CH4) and the net flux of CO2 across the surfaces of 15 boreal and subarctic lakes of different humic contents. Sediment respiration measurements were made in situ under ambient light conditions. The flux of CO2 between sediment and water varied between an uptake of 53 and an efflux of 182 mg C m−2 day−1 from the sediments. The mean respiration rate for sediments in contact with the upper mixed layer (SedR) was positively correlated to dissolved organic carbon (DOC) concentration in the water (r 2 = 0.61). The net flux of CO2 across the lake surface [net ecosystem exchange (NEE)] was also closely correlated to DOC concentration in the upper mixed layer (r 2 = 0.73). The respiration in the water column was generally 10-fold higher per unit lake area compared to sediment respiration. Lakes with DOC concentrations <5.6 mg L−1 had net consumption of CO2 in the sediments, which we ascribe to benthic primary production. Only lakes with very low DOC concentrations were net autotrophic (<2.6 mg L−1) due to the dominance of dissolved allochthonous organic carbon in the water as an energy source for aquatic organisms. In addition to previous findings of allochthonous organic matter as an important driver of heterotrophic metabolism in the water column of lakes, this study suggests that sediment metabolism is also highly dependent on allochthonous carbon sources.
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| 3. |
- An, Yueqing, 1994-, et al.
(författare)
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Host Phylogeny Structures the Gut Bacterial Community Within Galerucella Leaf Beetles
- 2023
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Ingår i: Microbial Ecology. - 0095-3628 .- 1432-184X. ; 86:4, s. 2477-2487
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Tidskriftsartikel (refereegranskat)abstract
- Gut microbes play important roles for their hosts. Previous studies suggest that host-microbial systems can form long-term associations over evolutionary time and the dynamic changes of the intestinal system may represent major driving forces and contribute to insect dietary diversification and speciation. Our study system includes a set of six closely related leaf beetle species (Galerucella spp.) and our study aims to separate the roles of host phylogeny and ecology in determining the gut microbial community and to identify eventual relationship between host insects and gut bacteria. We collected adult beetles from their respective host plants and quantified their microbial community using 16S rRNA sequencing. The results showed that the gut bacteria community composition was structured by host beetle phylogeny, where more or less host-specific gut bacteria interact with the different Galerucella species. For example, the endosymbiotic bacteria Wolbachia was found almost exclusively in G. nymphaea and G. sagittariae. Diversity indicators also suggested that α- and β-diversities of gut bacteria communities varied among host beetle species. Overall, our results suggest a phylogenetically controlled co-occurrence pattern between the six closely related Galerucella beetles and their gut bacteria, indicating the potential of co-evolutionary processes occurring between hosts and their gut bacterial communities.
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| 4. |
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| 5. |
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| 6. |
- Anesio, Alexandre Magno, et al.
(författare)
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Bacterial growth on photochemically transformed leachates from aquatic and terrestrial primary producers
- 2000
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 1432-184X .- 0095-3628. ; 40:3, s. 200-208
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Tidskriftsartikel (refereegranskat)abstract
- We measured bacterial growth on phototransformed dissolved organic matter (DOM) leached from eight different primary producers. Leachates (10 mg C liter(-1)) were exposed to artificial UVA + UVB radiation, or kept in darkness, for 20 h. DOM solutions were subsequently inoculated with lake water bacteria. Photoproduction of dissolved inorganic carbon (DIC), ranging from 3 to 16 mug C liter(-1) h(-1), and changes in the absorptive characteristics of the DOM were observed for all leachates upon UV irradiation. The effects of irradiation exposure on DOM bioavailability varied greatly, depending on leachate and type of bacterial growth criterion. Bacterial carbon utilization (biomass production plus respiration) over the entire incubation period (120 h) was enhanced by UV radiation of leachate from the terrestrial leaves, relative to carbon utilization in non-irradiated leachates. Conversely, carbon utilization was reduced by radiation of the leachates from aquatic macrophytes. In a separate experiment, the stable C and N isotope composition of bacteria grown on irradiated and non-irradiated DOM was estimated. Bacterial growth on UV-irradiated DOM was enriched in C-13 relative to the bacteria in the non-irradiated treatments; this result may be explained by selective assimilation of photochemically produced, isotopically enriched labile compounds.
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| 7. |
- Arias, A., et al.
(författare)
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Predator Chemical Cue Effects on the Diel Feeding Behaviour of Marine Protists
- 2021
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 82:2, s. 356-364
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Tidskriftsartikel (refereegranskat)abstract
- We have assessed the effect of copepod chemical cues on the diel feeding rhythms of heterotrophic and mixotrophic marine protists. All phagotrophic protists studied exhibited relatively high diurnal feeding rates. The magnitude of the diel feeding rhythm, expressed as the quotient of day and night ingestion rates, was inversely related to the time that phagotrophic protists were maintained in the laboratory in an environment without predators. In the case of the recently isolated ciliate Strombidium arenicola, the rhythm was lost after a few months. When challenged with chemical alarm signals (copepodamides) from the copepod Calanus finmarchicus at realistic concentrations (0.6-6 pM), S. arenicola partially re-established diurnal feeding. Conversely, the amplitude of the diel feeding rhythm for the ciliate Mesodinium rubrum was not affected by copepodamides, although the 24-h integrated food intake increased by approximately 23%. For the dinoflagellates Gyrodinium dominans and Karlodinium armiger, copepodamides significantly reduced the amplitude of their diel feeding rhythms; significant positive effects on total daily ingestion were only observed in G. dominans. Finally, the dinoflagellate Oxyrrhis marina, isolated >20 years ago, showed inconsistent responses to copepodamides, except for an average 6% increase in its total ingestion over 24 h. Our results demonstrate that the predation risk by copepods affects the diel feeding rhythm of marine protists and suggests a species-specific response to predation threats.
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| 8. |
- Axelsson, Karolin, et al.
(författare)
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Antifeedants Produced by Bacteria Associated with the Gut of the Pine Weevil Hylobius abietis
- 2017
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Ingår i: Microbial Ecology. - : SPRINGER. - 0095-3628 .- 1432-184X. ; 74:1, s. 177-184
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Tidskriftsartikel (refereegranskat)abstract
- The pine weevil, Hylobius abietis, is a severe forest pest insect as it feeds on newly planted conifer seedlings. To identify and develop an antifeedant could be one step towards the protection of seedlings from feeding damage by the pine weevil. With the aim to trace the origin of the antifeedants previously found in feces of the pine weevil, we investigated the culturable bacteria associated with the gut and identified the volatiles they produced. Bacterial isolates were identified by 16S ribosomal RNA gene analysis. The volatile emissions of selected bacteria, cultivated on NB media or on the grated phloem of Scots pine twigs dispersed in water, were collected and analyzed by solid-phase microextraction gas chromatography-mass spectrometry. The bacterial isolates released a variety of compounds, among others 2-methoxyphenol, 2-phenylethanol, 3-methyl-1-butanol, 1-octen-3-ol, 3-octanone, dimethyl disulfide, and dimethyl trisulfide. A strong antifeedant effect was observed by 2-phenylethanol, which could thus be a good candidate for use to protect planted conifer seedlings against feeding damage caused by H. abietis.
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| 10. |
- Backman, Agneta, et al.
(författare)
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Degradation of 4-chlorophenol at low temperature and during extreme temperature fluctuations by Arthrobacter chlorophenolicus A6
- 2004
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 48:2, s. 246-253
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Tidskriftsartikel (refereegranskat)abstract
- Low average temperatures and temperature fluctuations in temperate soils challenge the efficacy of microbial strains used for clean up of pollutants. In this study, we investigated the cold tolerance of Arthrobacter chlorophenolicus A6, a microorganism previously shown to degrade high concentrations of 4-chlorophenol at 28degreesC. Luciferase activity from a luc-tagged derivative of the strain (A6L) was used to monitor the metabolic status of the population during 4-chlorophenol degradation. The A6L strain could degrade 200-300 mug mL(-1) 4-chlorophenol in pure cultures incubated at 5degreesC, although rates of degradation, growth and the metabolic status of the cells were lower at 5degreesC compared to 28degreesC. When subjected to temperature fluctuations between 5 and 28degreesC, A6L continued to degrade 4-chlorophenol and remained active. In soil microcosm experiments, the degradation rates were significantly faster the first week at 28degreesC, compared to 5degreesC. However, this difference was no longer seen after 7 days, and equally low 4-chlorophenol concentrations were reached after 17 days at both temperatures. During 4-chlorophenol degradation in soil, CFU and luciferase activity values remained constant at both 5 and 28degreesC. However, once most of the 4-chlorophenol was degraded, both values decreased by 1-1.5 logarithmic values at 28degreesC, whereas they remained constant at 5degreesC, indicating a high survival of the cells at low temperatures. Because of the ability of A. chlorophenolicus A6 to degrade high concentrations of 4-chlorophenol at 5degreesC, together with its tolerance to temperature fluctuations and stress conditions found in soil, this strain is a promising candidate for bioaugmentation of chlorophenol-contaminated soil in temperate climates.
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