A Crispy Diet: Grazers of Achromatium oxaliferum in Lake Stechlin Sediments

Schorn, Sina; Cypionka, Heribert

doi:10.1007/s00248-018-1158-4

Cited by 6 publications

(3 citation statements)

References 17 publications

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“…2b,3b,4b,S3,and S4b). Most recently, a study on grazers of Achromatium in freshwater Lake Stechlin in Germany noticed that meiofaunal predators only hunt the smallest Achromatium cells and store them in their low-pH food vacuoles, presumably for calcite dissolution (Schorn and Cypionka 2018). Apparently, hardto-digest calcite inclusions combined with large cell size provides Achromatium with some protection against meiofaunal grazing.…”

Section: Discussion: a Scenario For Calcite Granule Dynamicsmentioning

confidence: 99%

Intracellular calcite and sulfur dynamics of Achromatium cells observed in a lab-based enrichment and aerobic incubation experiment

Yang

Teske

Ambrose

et al. 2018

Antonie van Leeuwenhoek

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We investigated the intracellular dynamics of calcite and sulfur in the large sulfur-oxidizing, calcite-accumulating bacterium Achromatium, with an emphasis on oxygen exposure as a physiological control. For this purpose, morphological changes and possible accretion mechanisms of calcite granules in cells that were freshly collected from natural Achromatium-containing sediment were compared to cells from the same source after prolonged exposure to atmospheric oxygen. Intracellular sulfur is oxidized and removed in response to oxygen exposure. Calcite granules also undergo distinct oxygen-related dynamics; they alternate between tightly packaged, smooth granules with narrow but sharply defined interstitial spaces in atmospheric oxygen-exposed cells, and more loosely packaged granules with irregular, bumpy surface texture and larger interstitial spaces in cells that were not artificially exposed to oxygen. These results suggest that morphological changes of the calcite granules reflect their changing physiological role inside the cell. Sulfur oxidation and calcite dissolution appear to be linked in that proton generation during sulfur oxidation is buffered by gradual calcite erosion, visible in the smooth, rounded surface morphology observed after oxygen exposure. Our results support the hypothesis that calcite dynamics buffer the intracellular pH fluctuations linked to electron acceptor limitation during proton-consuming sulfide oxidation to sulfur, and electron acceptor abundance during proton-generating sulfur oxidation to sulfate.

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Section: Discussion: a Scenario For Calcite Granule Dynamicsmentioning

confidence: 99%

Intracellular calcite and sulfur dynamics of Achromatium cells observed in a lab-based enrichment and aerobic incubation experiment

Yang

Teske

Ambrose

et al. 2018

Antonie van Leeuwenhoek

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“…Antagonism between bacteria and fungi has been shown to be often connected to direct resource competition 125 . Recently, even direct trophic interactions between the largest freshwater bacterium Achromatium and chytrid fungi have been observed 126 (FIG. 4).…”

Section: Box 1: Biotic Interactions With Aquatic Fungimentioning

confidence: 99%

Fungi in aquatic ecosystems

et al. 2019

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Fungi are phylogenetically and functionally diverse ubiquitous components of almost all ecosystems on Earth, including aquatic environments stretching from high montane lakes down to the deep ocean. Aquatic ecosystems, however, remain frequently overlooked as fungal habitats, although fungi potentially hold important roles for organic matter cycling and food web dynamics. Within a broad ecological framework, we conceptualize the spatio-temporal dimensions, diversity, functions and organismic interactions of fungi in structuring aquatic foodwebs. We focus on currently unexplored fungal diversity, highlighting poorly understood ecosystems, including emerging artificial aquatic habitats. Recent methodological improvements have facilitated a greater appreciation of the importance of fungi in many aquatic systems, yet a conceptual framework is still missing. To date, aquatic fungi and their interactions have largely remained "hidden" and require interdisciplinary efforts to be explored in an ecosystem context. There remain obvious methodological and knowledge gaps to explore potential functions of aquatic fungi, moving from the microscale to the global scale. This knowledge is urgently needed since we humans strongly interfere with structure and function of natural ecosystems by permanently reshaping most of the Earth's surface and creating vast areas of novel urban habitats. Introduction: Recent advances in DNA sequencing technology have revealed that fungi are abundant in many, if not all aquatic ecosystems, however their diversity, quantitative abundance, ecological function and, in particular, their interactions with other microorganisms, remain largely speculative, unexplored and missing from current general concepts in aquatic ecology and biogeochemistry 1-4. This is surprising since terrestrial-focused research has understood the outstanding ecological role of fungi for >100 years, and therefore fungi constitute a major component of general concepts in terrestrial science 5,6. In aquatic ecosystems, the systematic analysis of fungal diversity and their ecological roles has faced several setbacks due to methodological limitations and a too small scientific community, in particular in the marine environment 7-11. This review focusses on aquatic fungi, which form a morphologically, phylogenetically, and ecologically diverse group 7. We here broadly define "aquatic fungi" as fungi that rely for the whole or part of their life cycle on aquatic habitats (FIG. 1). Three groups (indwellers, periodic immigrants and versatile immigrants) based on their degree of adaptation and dependence on aquatic habitats have been previously defined 12. We highlight the numerous knowledge gaps in their diversity, interactions and functional roles, as well as methodological limitations. In this review we propose new research avenues to set aquatic fungi in a broad ecological framework. Here, we do not explore the many existing gaps in the fungal phylogenetic tree. In aquatic systems, fungi constitute a significant proportion of eukaryo...

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“…(2015) analyzed Ca‐carbonate granules in situ within Achromatium cells by Raman microspectroscopy and also concluded that they were calcite crystals. Consistently, most recent studies assumed that intracellular granules were calcite crystals based on the latest reports in the literature (e.g., Babenzien et al, 2015; Ionescu et al., 2017; Mansor et al., 2015; Schorn & Cypionka, 2018; Yang et al., 2019). Yet, the observations by West and Griffiths (1913) suggesting that Achromatium CaCO 3 granules are composed of ACC seem precisely documented.…”

Section: Introductionmentioning

confidence: 73%

The gammaproteobacterium Achromatium forms intracellular amorphous calcium carbonate and not (crystalline) calcite

et al. 2020

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Achromatium is a long known uncultured giant gammaproteobacterium forming intracellular CaCO3 that impacts C and S geochemical cycles functioning in some anoxic sediments and at oxic‐anoxic boundaries. While intracellular CaCO3 granules have first been described as Ca oxalate then colloidal CaCO3 more than one century ago, they have often been referred to as crystalline solids and more specifically calcite over the last 25 years. Such a crystallographic distinction is important since the respective chemical reactivities of amorphous calcium carbonate (ACC) and calcite, hence their potential physiological role and conditions of formation, are significantly different. Here, we analyzed the intracellular CaCO3 granules of Achromatium cells from Lake Pavin using a combination of Raman microspectroscopy and scanning electron microscopy. Granules in intact Achromatium cells were unequivocally composed of ACC. Moreover, ACC spontaneously transformed into calcite when irradiated at high laser irradiance during Raman analyses. Few ACC granules also transformed spontaneously into calcite in lysed cells upon cell death and/or sample preparation. Overall, the present study supports the original claims that intracellular Ca‐carbonates in Achromatium are amorphous and not crystalline. In that sense, Achromatium is similar to a diverse group of Cyanobacteria and a recently discovered magnetotactic alphaproteobacterium, which all form intracellular ACC. The implications for the physiology and ecology of Achromatium are discussed. Whether the mechanisms responsible for the preservation of such unstable compounds in these bacteria are similar to those involved in numerous ACC‐forming eukaryotes remains to be discovered. Last, we recommend to future studies addressing the crystallinity of CaCO3 granules in Achromatium cells recovered from diverse environments all over the world to take care of the potential pitfalls evidenced by the present study.

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A Crispy Diet: Grazers of Achromatium oxaliferum in Lake Stechlin Sediments

Cited by 6 publications

References 17 publications

Intracellular calcite and sulfur dynamics of Achromatium cells observed in a lab-based enrichment and aerobic incubation experiment

Intracellular calcite and sulfur dynamics of Achromatium cells observed in a lab-based enrichment and aerobic incubation experiment

Fungi in aquatic ecosystems

The gammaproteobacterium Achromatium forms intracellular amorphous calcium carbonate and not (crystalline) calcite

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