Eukaryotic Picoplankton in Surface Oceans

Massana, Ramón

doi:10.1146/annurev-micro-090110-102903

Cited by 233 publications

(211 citation statements)

References 89 publications

(57 reference statements)

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“…to either the SAR or CCTH clade (23), which is consistent with our geochemical data. The SAR and CCTH clades include various phototrophic and mixotrotrophic protists other than the obligate heterotrophs analyzed here.…”

Section: Resultssupporting

confidence: 92%

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Ubiquity and quantitative significance of detoxification catabolism of chlorophyll associated with protistan herbivory

Kashiyama

Yokoyama²,

Kinoshita

et al. 2012

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

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Chlorophylls are essential components of the photosynthetic apparati that sustain all of the life forms that ultimately depend on solar energy. However, a drawback of the extraordinary photosensitizing efficiency of certain chlorophyll species is their ability to generate harmful singlet oxygen. Recent studies have clarified the catabolic processes involved in the detoxification of chlorophylls in land plants, but little is understood about these strategies in aquatic ecosystem. Here, we report that a variety of heterotrophic protists accumulate the chlorophyll a catabolite 13 2 ,17 3 -cyclopheophorbide a enol (cPPB-aE) after their ingestion of algae. This chlorophyll derivative is nonfluorescent in solution, and its inability to generate singlet oxygen in vitro qualifies it as a detoxified catabolite of chlorophyll a. Using a modified analytical method, we show that cPPBaE is ubiquitous in aquatic environments, and it is often the major chlorophyll a derivative. Our findings suggest that cPPB-aE metabolism is one of the most important, widely distributed processes in aquatic ecosystems. Therefore, the herbivorous protists that convert chlorophyll a to cPPB-aE are suggested to play more significant roles in the modern oceanic carbon flux than was previously recognized, critically linking microscopic primary producers to the macroscopic food web and carbon sequestration in the ocean. phototoxicity of chlorophylls | microbial herbivory | phagocytosis | biodiversity of eukaryotes | microbial loop C hlorophylls are crucial to sustaining most life forms on Earth, the majority of which ultimately depend on solar energy. Photoexcitation of chlorophylls initiates various photosynthetic reactions that convert the energy of photons into chemical potentials, which in turn, drive the full range of metabolic reactions throughout the global ecosystem. Chlorophylls play a central role in the photosynthetic apparatus by absorbing light and transferring the excitation energy to the reaction centers of photosystems before photosynthetic electron transport. However, without measures to contain the excited energy, chlorophylls can harm organisms because of their high photosensitizing potential.

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Section: Resultssupporting

confidence: 92%

“…Importance of protistan herbivory as a part of the microbial loop in aquatic environments has been recognized for nearly three decades (25). During this time, the quantitative significance of picophytoplankton (ϕ ≤ 3 μm) has also been revealed (23,24). Picophytoplankton includes coccoidal cyanobacteria and eukaryotic picophytoplankton.…”

Section: Resultsmentioning

confidence: 99%

Ubiquity and quantitative significance of detoxification catabolism of chlorophyll associated with protistan herbivory

Kashiyama

Yokoyama²,

Kinoshita

et al. 2012

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

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“…Among heterotrophic protists, small flagellates (1-5 mm) constitute a key link between bacteria and larger protists, transferring organic carbon to upper trophic levels (Jurgens and Massana, 2008;Massana, 2011). Furthermore, heterotrophic pico-and nano-sized flagellates together with viruses are important control agents of planktonic bacteria in the oceans (Suttle, 2005;Jurgens and Massana, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, heterotrophic pico-and nano-sized flagellates together with viruses are important control agents of planktonic bacteria in the oceans (Suttle, 2005;Jurgens and Massana, 2008). Pico-and nano-flagellates have been traditionally considered in bulk, but data gathered during the last decade show that they constitute an evolutionarily very diverse assemblage (Massana, 2011). Despite the large ecological importance of heterotrophic pico-and nano-flagellates, the actual diversity of the different groups as well as the distribution of diversity in space and time are among the least known within the microbial world.…”

Section: Introductionmentioning

confidence: 99%

Diversity patterns and activity of uncultured marine heterotrophic flagellates unveiled with pyrosequencing

et al. 2012

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Flagellated heterotrophic microeukaryotes have key roles for the functioning of marine ecosystems as they channel large amounts of organic carbon to the upper trophic levels and control the population sizes of bacteria and archaea. Still, we know very little on the diversity patterns of most groups constituting this evolutionary heterogeneous assemblage. Here, we investigate 11 groups of uncultured flagellates known as MArine STramenopiles (MASTs). MASTs are ecologically very important and branch at the base of stramenopiles. We explored the diversity patterns of MASTs using pyrosequencing (18S rDNA) in coastal European waters. We found that MAST groups range from highly to lowly diversified. Pyrosequencing (hereafter '454') allowed us to approach to the limits of taxonomic diversity for all MAST groups, which varied in one order of magnitude (tens to hundreds) in terms of operational taxonomic units (98% similarity). We did not evidence large differences in activity, as indicated by ratios of DNA:RNA-reads. Most groups were strictly planktonic, although we found some groups that were active in sediments and even in anoxic waters. The proportion of reads per size fraction indicated that most groups were composed of very small cells (B2-5 lm). In addition, phylogenetically different assemblages appeared to be present in different size fractions, depths and geographic zones. Thus, MAST diversity seems to be highly partitioned in spatial scales. Altogether, our results shed light on these ecologically very important but poorly known groups of uncultured marine flagellates.

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“…(11,12). Nevertheless, it appears likely that picoeukaryotes independently emerged via reductive evolution in different lines of descent.…”

mentioning

confidence: 99%

Energetics and population genetics at the root of eukaryotic cellular and genomic complexity

Koonin

2015

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

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Eukaryotic Picoplankton in Surface Oceans

Cited by 233 publications

References 89 publications

Ubiquity and quantitative significance of detoxification catabolism of chlorophyll associated with protistan herbivory

Ubiquity and quantitative significance of detoxification catabolism of chlorophyll associated with protistan herbivory

Diversity patterns and activity of uncultured marine heterotrophic flagellates unveiled with pyrosequencing

Energetics and population genetics at the root of eukaryotic cellular and genomic complexity

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