Anaerobic free-living protozoa: growth efficiencies and the structure of anaerobic communities

Fenchel, Tom; Finlay, Bland J.

doi:10.1111/j.1574-6941.1990.tb01693.x

Cited by 43 publications

(65 citation statements)

References 16 publications

(14 reference statements)

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“…In Lake Suigetsu, the biomass ratios between HNF and bacteria in the anoxic layer (mean ± SD: 0.04 ± 0.02) were lower than those in the oxic (0.19 ± 0.16) and the suboxic layer (0.18 ± 0.15). Thus, our observations corroborate those of Fenchel & Finlay (1990), suggesting that the growth efficiency of HNF in the anoxic layer is low.…”

Section: Discussionsupporting

confidence: 81%

“…This suggests HNF may have the highest position in the food chain in the anoxic hypolimnion of the lake and that top-down control is less important for HNF abundance. Fenchel & Finlay (1990) report that the biomass ratios between protozoa and bacteria in anoxic waters were 3 to 7 times lower than those in aerobic systems, suggesting a low growth efficiency of anaerobic protozoa. In Lake Suigetsu, the biomass ratios between HNF and bacteria in the anoxic layer (mean ± SD: 0.04 ± 0.02) were lower than those in the oxic (0.19 ± 0.16) and the suboxic layer (0.18 ± 0.15).…”

Section: Discussionmentioning

confidence: 99%

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Abundance and bacterivory of heterotrophic nanoflagellates in the meromictic Lake Suigetsu, Japan

Okamura¹,

Mori²,

Nakano³

et al. 2012

Aquat. Microb. Ecol.

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The abundance and bacterivory of heterotrophic nanoflagellates (HNF) were seasonally followed in the oxic and anoxic layers of the meromictic Lake Suigetsu between May 2008 and November 2010. The HNF abundance in the anoxic layer was always lower than in the oxic layer during the study period. Ingestion of fluorescently labeled 0.5 µm diameter beads by the anaerobic HNF in the anoxic layer indicated bacterivory by HNF. The specific ingestion rates in the anoxic layers were generally similar to those taken from the oxic layer, with some exceptions. Our data thus suggested that anaerobic HNF were bacterial consumers with high potential bacterivory comparable to that of aerobic HNF in Lake Suigetsu. Bacterial turnover rates by HNF grazing in the oxic layer were estimated to be as high as ~10% d −1 of the bacterial standing stock. In contrast, the rates in the anoxic layer were <1% d −1 due to the low density of HNF in the anoxic layer. Our data thus provide a valuable contribution to understanding the structure and function of microbial food webs in anoxic aquatic environments.

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

Abundance and bacterivory of heterotrophic nanoflagellates in the meromictic Lake Suigetsu, Japan

Okamura¹,

Mori²,

Nakano³

et al. 2012

Aquat. Microb. Ecol.

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“…The relative abundance of these species might have been influenced by an enhanced predation pressure in the system. C. okenii could have been subjected to a higher predation pressure by anaerobic protozoa and predatory prokaryotes (23,32). Growing in net-like structures or large aggregates, C. clathratiforme and L. purpurea are less susceptible to protozoan grazers than are the single cells of C. okenii (33,34).…”

Section: Resultsmentioning

confidence: 99%

A single-cell view on the ecophysiology of anaerobic phototrophic bacteria

Musat

Halm

Winterholler

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

391

421

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Quantitative information on the ecophysiology of individual microorganisms is generally limited because it is difficult to assign specific metabolic activities to identified single cells. Here, we develop and apply a method, Halogen In Situ HybridizationSecondary Ion Mass Spectroscopy (HISH-SIMS), and show that it allows simultaneous phylogenetic identification and quantitation of metabolic activities of single microbial cells in the environment. Using HISH-SIMS, individual cells of the anaerobic, phototropic bacteria Chromatium okenii, Lamprocystis purpurea, and Chlorobium clathratiforme inhabiting the oligotrophic, meromictic Lake Cadagno were analyzed with respect to H 13 CO3 ؊ and 15 NH4 ؉ assimilation. Metabolic rates were found to vary greatly between individual cells of the same species, showing that microbial populations in the environment are heterogeneous, being comprised of physiologically distinct individuals. Furthermore, C. okenii, the least abundant species representing Ϸ0.3% of the total cell number, contributed more than 40% of the total uptake of ammonium and 70% of the total uptake of carbon in the system, thereby emphasizing that numerically inconspicuous microbes can play a significant role in the nitrogen and carbon cycles in the environment. By introducing this quantification method for the ecophysiological roles of individual cells, our study opens a variety of possibilities of research in environmental microbiology, especially by increasing the ability to examine the ecophysiological roles of individual cells, including those of less abundant and less active microbes, and by the capacity to track not only nitrogen and carbon but also phosphorus, sulfur, and other biological element flows within microbial communities.anaerobic phototrophs ͉ nanoSIMS

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“…Metopus contortus, a free-living ciliate, is a ubiquitous filter-feeder in anoxic marine sediments which plays a vital role in the phagotrophic chains of anaerobic communities (Fenchel & Finlay, 1990). It does not have mitochondria, but it does have specialized redox organelles, the hydrogenosomes, which release hydrogen gas (Finlay & Fenchel, 1989;.…”

Section: Introductionmentioning

confidence: 99%

Hydrogenosomes of Metopus contortus physiologically resemble mitochondria

et al. 1997

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The anaerobic free-living ciliated protozoon Metopus contortus is a grazer in anoxic marine sediments. It does not possess mitochondria, but it does have specialized organelles termed hydrogenosomes which release hydrogen gas. The cationic lipophilic cyanine dye DiOC,(3) is an indicator of transmembrane electrochemical potential. With the aid of confocal laser scanning microscopy (CLSM), the association of this dye with hydrogenosomes in situ was followed. Flow cytometric measurements showed that fluorescence of the membrane potential dye decreased in response to an elevated pH, in the cell. CLSM also revealed localization of fluorescence of the calcium probe Flu0 3-AM, and of the transmembrane pH gradient probe BCECF-AM, within the lumen of the hydrogenosomes. In addition, hydrogenosomal inclusions were detected. X-ray microanalysis of these electron-dense granules revealed high levels of calcium, phosphate and magnesium. It is concluded that M. contortus hydrogenosomes are calcium stores, have a membrane potential, and an alkaline lumen. These physiological features resemble those of mitochondria in aerobic protozoa.

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Anaerobic free-living protozoa: growth efficiencies and the structure of anaerobic communities

Cited by 43 publications

References 16 publications

Abundance and bacterivory of heterotrophic nanoflagellates in the meromictic Lake Suigetsu, Japan

Abundance and bacterivory of heterotrophic nanoflagellates in the meromictic Lake Suigetsu, Japan

A single-cell view on the ecophysiology of anaerobic phototrophic bacteria

Hydrogenosomes of Metopus contortus physiologically resemble mitochondria

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