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As chloroplast-stealing or "kleptoplastidic" lineages become more reliant on stolen machinery, they also tend to become more specialized on the prey from which they acquire this machinery. For example, the ciliate Mesodinium rubrum obtains > 95% of its carbon from photosynthesis, and specializes on plastids from the Teleaulax clade of cryptophytes. However, M. rubrum is sometimes observed in nature containing plastids from other cryptophyte species. Here, we report on substantial ingestion of the blue-green cryptophyte Hemiselmis pacifica by M. rubrum, leading to organelle retention and transient increases in M. rubrum's growth rate. However, microscopy data suggest that H. pacifica organelles do not experience the same rearrangement and integration as Teleaulax amphioxeia's. We measured M. rubrum's functional response, quantified the magnitude and duration of growth benefits, and estimated kleptoplastid photosynthetic rates. Our results suggest that a lack of discrimination between H. pacifica and the preferred prey T. amphioxeia (perhaps due to similarities in cryptophyte size and swimming behavior) may result in H. pacifica ingestion Thus, while blue-green cryptophytes may represent a negligible prey source in natural environments, they may help M. rubrum survive when Teleaulax are unavailable. Furthermore, these results represent a useful tool for manipulating M. rubrum's cell biology and photophysiology., (© 2024 The Author(s). Journal of Eukaryotic Microbiology published by Wiley Periodicals LLC on behalf of International Society of Protistologists.)

The Cryptomonad Guillardia theta has 42 genes encoding microbial rhodopsin-like proteins in their genomes. Light-driven ion-pump activity has been reported for some rhodopsins based on heterologous E. coli or mammalian cell expression systems. However, neither their physiological roles nor the expression of those genes in native cells are known. To reveal their physiological roles, we investigated the expression patterns of these genes under various growth conditions. Nitrogen (N) deficiency induced color change in exponentially growing G. theta cells from brown to green. The 29 rhodopsin-like genes were expressed in native cells. We found that the expression of 6 genes was induced under N depletion, while that of another 6 genes was reduced under N depletion., Competing Interests: The authors have declared that no competing interests exist.

The Baltic Sea summer phytoplankton community plays an important role in biogeochemical cycling and in the transfer of energy through the food web via zooplankton. We aimed to improve the understanding of the degree to which large-scale versus local environmental dynamics regulate phytoplankton dynamics by analyzing time series at the Baltic Sea scale. We used dynamic factor analysis to study if there are common patterns of interannual variation that are shared ("common trends") among summer phytoplankton total and class-level biomass time series observed across Baltic Sea latitudinal gradients in salinity and temperature. We evaluated alternative hypotheses regarding common trends among summer phytoplankton biomass: Baltic Sea-wide common trends; common trends by geography (latitude and basin); common trends differing among functional groups (phytoplankton classes); or common trends driven by both geography and functional group. Our results indicated little support for a common trend in total summer phytoplankton biomass. At a finer resolution, classes had common trends that were most closely associated with the cryptophyte and cyanobacteria time series with patterns that differed between northern and southern sampling stations. These common trends were also very sensitive to two anomalous years (1990, 2008) of cryptophyte biomass. The Baltic Sea Index, a regional climate index, was correlated with two common class trends that shifted in mean state around the mid-1990s. The limited coherence in phytoplankton biomass variation over time despite known, large-scale, ecosystem shifts suggests that stochastic dynamics at local scales limits the ability to observe common trends at the scale of monitoring data collection., Competing Interests: The authors have declared that no competing interests exist.

Mesodinium spp. are commonly found in marine and brackish waters, and several species are known to contain red, green, or both plastids that originate from cryptophyte prey. We observed the seasonal succession of Mesodinium spp. in a Japanese brackish lake, and we analysed the origin and diversity of the various coloured plastids within the cells of Mesodinium spp. using a newly developed primer set that specifically targets the cryptophyte nuclear 18S rRNA gene. Mesodinium rubrum isolated from the lake contained only red plastids originating from cryptophyte Teleaulax amphioxeia. We identified novel Mesodinium sp. that contained only green plastids or both red and green plastids originating from cryptophytes Hemiselmis sp. and Teleaulax acuta. Although the morphology of the newly identified Mesodinium sp. was indistinguishable from that of M. rubrum under normal light microscopy, phylogenetic analysis placed this species between the M. rubrum/major species complex and a well-supported lineage of M. chamaeleon and M. coatsi. Close associations were observed in cryptophyte species composition within cells of Mesodinium spp. and in ambient water samples. The appearance of suitable cryptophyte prey is probably a trigger for succession of Mesodinium spp., and the subsequent abundance of Mesodinium spp. appears to be influenced by water temperature and dissolved inorganic nutrients.

For years the genus Chroomonas was defined as being a cryptophyte with rectangular periplast plates, with a gullet and with biliprotein types PC 630 or 645. In phylogenetic trees the genus proved to be paraphyletic. Moreover, cells with hexagonal periplast plates were found in an SEM preparation from material of the type species C. nordstedtii. In this study, material of Hansgirg's C. nordstedtii was subjected to PCR and to sequencing of two short DNA tags. These tags allowed for an unambiguous identification of the real C. nordstedtii in the phylogeny of the blue-green cryptophytes. The genus Chroomonas corresponds to subclade 1, whereas subclades 3 and 4 do not belong to Chroomonas, if Hemiselmis is maintained. Additional examination by light and scanning electron microscopy and by spectrophotometry demonstrate that subclade 1 comprises only cells with hexagonal periplast plates and PC 630, whereas rectangular periplast plates are found only in subclades 3 and 4. Consequently the genus Chroomonas and its type species, C. nordstedtii, are revised and two novel species, C. debatzensis and C. gentoftensis sp. nov., are described., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

The expanding aquaculture industry plays an important role in feeding the growing human population and with the expansion, sustainable bacterial disease control, such as probiotics, becomes increasingly important. Tropodithietic acid (TDA)-producing Phaeobacter spp. can protect live feed, for example rotifers and Artemia as well as larvae of turbot and cod against pathogenic vibrios. Here, we show that the emerging live feed, copepods, is unaffected by colonization of the fish pathogen Vibrio anguillarum, making them potential infection vectors. However, TDA-producing Phaeobacter inhibens was able to significantly inhibit V. anguillarum in non-axenic cultures of copepod Acartia tonsa and the copepod feed Rhodomonas salina. Vibrio grew to 10 6  CFU ml -1 and 10 7  CFU ml -1 in copepod and R. salina cultures, respectively. However, vibrio counts remained at the inoculum level (10 4  CFU ml -1 ) when P. inhibens was also added. We further developed a semi-strain-specific qPCR for V. anguillarum to detect and quantify the pathogen in non-axenic systems. In conclusion, P. inhibens efficiently inhibits the fish larval pathogen V. anguillarum in the emerging live feed, copepods, supporting its use as a probiotic in aquaculture. Furthermore, qPCR provides an effective method for detecting vibrio pathogens in complex non-axenic live feed systems., (© 2018 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.)

Twenty years ago an Arctic cryptophyte was isolated from Baffin Bay and given strain number CCMP2045. Here, it was described using morphology, water- and non-water soluble pigments and nuclear-encoded SSU rDNA. The influence of temperature, salinity, and light intensity on growth rates was also examined. Microscopy revealed typical cryptophyte features but the chloroplast color was either green or red depending on the light intensity provided. Phycoerythrin (Cr-PE 566) was only produced when cells were grown under low-light conditions (5 μmol photons · m -2  · s -1 ). Non-water-soluble pigments included chlorophyll a, c 2 and five major carotenoids. Cells measured 8.2 × 5.1 μm and a tail-like appendage gave them a comma-shape. The nucleus was located posteriorly and a horseshoe-shaped chloroplast contained a single pyrenoid. Ejectosomes of two sizes and a nucleomorph anterior to the pyrenoid were discerned in TEM. SEM revealed a slightly elevated vestibular plate in the vestibulum. The inner periplast component consisted of slightly overlapping hexagonal plates arranged in 16-20 oblique rows. Antapical plates were smaller and their shape less profound. Temperature and salinity studies revealed CCMP2045 as stenothermal and euryhaline and growth was saturated between 5 and 20 μmol photons · m -2  · s -1 . The phylogeny based on SSU rDNA showed that CCMP2045 formed a distinct clade with CCMP2293 and Falcomonas sp. isolated from Spain. Combining pheno- and genotypic data, the Arctic cryptophyte could not be placed in an existing family and genus and therefore Baffinellaceae fam. nov. and Baffinella frigidus gen. et sp. nov. were proposed., (© 2018 Phycological Society of America.)

Plants and algae have developed various light-harvesting mechanisms for optimal delivery of excitation energy to the photosystems. Cryptophyte algae have evolved a novel soluble light-harvesting antenna utilizing phycobilin pigments to complement the membrane-intrinsic Chl a/c-binding LHC antenna. This new antenna consists of the plastid-encoded β-subunit, a relic of the ancestral phycobilisome, and a novel nuclear-encoded α-subunit unique to cryptophytes. Together, these proteins form the active α 1 β·α 2 β-tetramer. In all cryptophyte algae investigated so far, the α-subunits have duplicated and diversified into a large gene family. Although there is transcriptional evidence for expression of all these genes, the X-ray structures determined to date suggest that only two of the α-subunit genes might be significantly expressed at the protein level. Using proteomics, we show that in phycoerythrin 545 (PE545) of Guillardia theta, the only cryptophyte with a sequenced genome, all 20 α-subunits are expressed when the algae grow under white light. The expression level of each protein depends on the intensity of the growth light, but there is no evidence for a specific light-dependent regulation of individual members of the α-subunit family under the growth conditions applied. GtcpeA10 seems to be a special member of the α-subunit family, because it consists of two similar N- and C-terminal domains, which likely are the result of a partial tandem gene duplication. The proteomics data of this study have been deposited to the ProteomeXchange Consortium and have the dataset identifiers PXD006301 and 10.6019/PXD006301.

Microalgae have the ability to synthetize many compounds, some of which have been recognized as a source of functional ingredients for nutraceuticals with positive health effects. One well-known example is the long-chain polyunsaturated fatty acids (PUFAs), which are essential for human nutrition. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the two most important long-chain omega-3 (ω-3) PUFAs involved in human physiology, and both industries are almost exclusively based on microalgae. In addition, algae produce phytosterols that reduce serum cholesterol. Here we determined the growth rates, biomass yields, PUFA and sterol content, and daily gain of eight strains of marine cryptophytes. The maximal growth rates of the cryptophytes varied between 0.34-0.70 divisions day -1 , which is relatively good in relation to previously screened algal taxa. The studied cryptophytes were extremely rich in ω-3 PUFAs, especially in EPA and DHA (range 5.8-12.5 and 0.8-6.1 µg mg dry weight -1 , respectively), but their sterol concentrations were low. Among the studied strains, Storeatula major was superior in PUFA production, and it also produces all PUFAs, i.e., α-linolenic acid (ALA), stearidonic acid (SDA), EPA, and DHA, which is rare in phytoplankton in general. We conclude that marine cryptophytes are a good alternative for the ecologically sustainable and profitable production of health-promoting lipids., Competing Interests: The authors declare no conflict of interest.

The underwater light field in blackwater environments is strongly skewed toward the red end of the electromagnetic spectrum due to blue light absorption by colored dissolved organic matter (CDOM). Exposure of phytoplankton to full spectrum irradiance occurs only when cells are mixed up to the surface. We studied the potential effects of mixing-induced changes in spectral irradiance on photoacclimation, primary productivity and growth in cultures of the cryptophyte Rhodomonas salina and the diatom Skeletonema costatum. We found that these taxa have very different photoacclimation strategies. While S. costatum showed classical complementary chromatic adaption, R. salina showed inverse chromatic adaptation, a strategy previously unknown in the cryptophytes. Transfer of R. salina to periodic full spectrum light (PFSL) significantly enhanced growth rate (μ) by 1.8 times and primary productivity from 0.88 to 1.35 mg C · (mg Chl -1 ) · h -1 . Overall, R. salina was less dependent on PFSL than was S. costatum, showing higher μ and net primary productivity rates. In the high-CDOM simulation, carbon metabolism of the diatom was impaired, leading to suppression of growth rate, short-term 14 C uptake and net primary production. Upon transfer to PFSL, μ of the diatom increased by up to 3-fold and carbon fixation from 2.4 to 6.0 mg C · (mg Chl -1 ) · h -1 . Thus, a lack of PFSL differentially impairs primarily CO 2 -fixation and/or carbon metabolism, which, in turn, may determine which phytoplankton dominate the community in blackwater habitats and may therefore influence the structure and function of these ecosystems., (© 2017 Phycological Society of America.)

In a previous study, Teleaulax amphioxeia-the preferred prey of Mesodinium in the Columbia River estuary-were undetectable within intense annual blooms, suggesting blooms are prey-limited or prey are acquired outside of bloom patches. We used a novel molecular approach specifically targeting the prey (i.e., Unique Sequence Element [USE] within the ribosomal RNA 28S D2 regions of T. amphioxeia nucleus and nucleomorph) in estuarine water samples acquired autonomously with an Environmental Sample Processor integrated within a monitoring network (ESP-SATURN). This new approach allowed for both more specific detection of the prey and better constraint of sample variability. A positive correlation was observed between abundances of M. cf. major and T. amphioxeia during bloom periods. The correlation was stronger at depth (> 8.2 m) and weak or nonexistent in the surface, suggesting that predator-prey dynamics become uncoupled when stratification is strong. We confirmed exclusive selectivity for T. amphioxeia by M. cf. major and observed the incorporation of the prey nucleus into a 4-nuclei complex, where it remained functionally active. The specific biomarker for T. amphioxeia was also recovered in M. cf. major samples from a Namibian coastal bloom, suggesting that a specific predator-prey relationship might be widespread between M. cf. major and T. amphioxeia., (© 2017 The Author(s) Journal of Eukaryotic Microbiology © 2017 International Society of Protistologists.)

We studied the diversity of Limnohabitans using reverse line blot hybridization with Limnohabitans lineage-specific probes in the freshwater canyon-shaped Římov reservoir (Czech Republic). To examine the succession of distinct lineages, we performed (i) a study of an intensive spring sampling program at the lacustrine part of the Římov reservoir (from ice melt through a phytoplankton peak to the clear-water phase), and (ii) a seasonal study (April to November) when the occurrence of distinct Limnohabitans lineages was related to the inherent longitudinal heterogeneity of the reservoir. Significant spatiotemporal changes in the compositions of distinct Limnohabitans lineages allowed for the identification of "generalists" that were always present throughout the whole season as well as "specialists" that appeared in the reservoir only for limited periods of time or irregularly. Our results indicate that some phytoplankton groups, such as cryptophytes or cyanobacteria, and zooplankton composition were the major factors modulating the distribution and dynamics of distinct Limnohabitans lineages. The highest Limnohabitans diversity was observed during the spring algal bloom, whereas the lowest was during the summer cyanobacterial bloom. The microdiversity also markedly increased upstream in the reservoir, being highest at the inflow, and thus likely reflecting strong influences of the watershed. IMPORTANCE The genus Limnohabitans is a typical freshwater bacterioplankton and is believed to play a significant role in inland freshwater habitats. This work is unique in detecting and tracing different closely related lineages of this bacterial genus in its natural conditions using the semiquantitative reverse line blot hybridization method and in discovering the factors influencing the microdiversity, subtype alternations, and seasonality., (Copyright © 2017 American Society for Microbiology.)

The acidification of the oceans could potentially alter marine plankton communities with consequences for ecosystem functioning. While several studies have investigated effects of ocean acidification on communities using traditional methods, few have used genetic analyses. Here, we use community barcoding to assess the impact of ocean acidification on the composition of a coastal plankton community in a large scale, in situ, long-term mesocosm experiment. High-throughput sequencing resulted in the identification of a wide range of planktonic taxa (Alveolata, Cryptophyta, Haptophyceae, Fungi, Metazoa, Hydrozoa, Rhizaria, Straminipila, Chlorophyta). Analyses based on predicted operational taxonomical units as well as taxonomical compositions revealed no differences between communities in high CO2 mesocosms (~ 760 μatm) and those exposed to present-day CO2 conditions. Observed shifts in the planktonic community composition were mainly related to seasonal changes in temperature and nutrients. Furthermore, based on our investigations, the elevated CO2 did not affect the intraspecific diversity of the most common mesozooplankter, the calanoid copepod Pseudocalanus acuspes. Nevertheless, accompanying studies found temporary effects attributed to a raise in CO2. Differences in taxa composition between the CO2 treatments could, however, only be observed in a specific period of the experiment. Based on our genetic investigations, no compositional long-term shifts of the plankton communities exposed to elevated CO2 conditions were observed. Thus, we conclude that the compositions of planktonic communities, especially those in coastal areas, remain rather unaffected by increased CO2.

Protist-alga symbiosis is widespread in the ocean, but its characteristics and function in situ remain largely unexplored. Here we report the symbiosis of the ciliate Mesodinium rubrum with cryptophyte cells during a red-tide bloom in Long Island Sound. In contrast to the current notion that Mesodinium retains cryptophyte chloroplasts or organelles, our multiapproach analyses reveal that in this bloom the endosymbiotic Teleaulax amphioxeia cells were intact and expressing genes of membrane transporters, nucleus-to-cytoplasm RNA transporters, and all major metabolic pathways. Among the most highly expressed were ammonium transporters in both organisms, indicating cooperative acquisition of ammonium as a major N nutrient, and genes for photosynthesis and cell division in the cryptophyte, showing active population proliferation of the endosymbiont. We posit this as a "Mesodinium-farming-Teleaulax" relationship, a model of protist-alga symbiosis worth further investigation by metatranscriptomic technology., Competing Interests: The authors declare no conflict of interest.

Plants and algae have developed various regulatory mechanisms for optimal delivery of excitation energy to the photosystems even during fluctuating light conditions; these include state transitions as well as non-photochemical quenching. The former process maintains the balance by redistributing antennae excitation between the photosystems, meanwhile the latter by dissipating excessive excitation inside the antennae. In the present study, these mechanisms have been analysed in the cryptophyte alga Guillardia theta. Photoprotective non-photochemical quenching was observed in cultures only after they had entered the stationary growth phase. These cells displayed a diminished overall photosynthetic efficiency, measured as CO2 assimilation rate and electron transport rate. However, in the logarithmic growth phase G. theta cells redistributed excitation energy via a mechanism similar to state transitions. These state transitions were triggered by blue light absorbed by the membrane integrated chlorophyll a/c antennae, and green light absorbed by the lumenal biliproteins was ineffective. It is proposed that state transitions in G. theta are induced by small re-arrangements of the intrinsic antennae proteins, resulting in their coupling/uncoupling to the photosystems in state 1 or state 2, respectively. G. theta therefore represents a chromalveolate algae able to perform state transitions., (© The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

The cryptomonad Rhinomonas nottbecki n. sp., isolated from the Baltic Sea, is described from live and fixed cells studied by light, scanning, and transmission electron microscopy together with sequences of the partial nucleus- and nucleomorph-encoded 18S rRNA genes as well as the nucleus-encoded ITS1, 5.8S, ITS2, and the 5'-end of the 28S rRNA gene regions. The sequence analyses include comparison with 43 strains from the family Pyrenomonadaceae. Rhinomonas nottbecki cells are dorsoventrally flattened, obloid in shape; 10.0-17.2 μm long, 5.5-8.1 μm thick, and 4.4-8.8 μm wide. The inner periplast has roughly hexagonal plates. Rhinomonas nottbecki cells resemble those of Rhinomonas reticulata, but the nucleomorph 18S rRNA gene of R. nottbecki differs by 2% from that of R. reticulata, while the ITS region by 11%. The intraspecific variability in the ITS region of R. nottbecki is 5%. In addition, the predicted ITS2 secondary structures are different in R. nottbecki and R. reticulata. The family Pyrenomonadaceae includes three clades: Clade A, Clade B, and Clade C. All Rhinomonas sequences branched within the Clade C, while the genus Rhodomonas is paraphyletic. The analyses suggest that the genus Storeatula is an alternating morphotype of the genera Rhinomonas and Rhodomonas and that the family Pyrenomonadaceae includes some species that were described multiple times, as well as novel species., (© 2014 The Author(s) Journal of Eukaryotic Microbiology © 2014 International Society of Protistologists.)

The trophic interactions between viruses, bacteria and protists play a crucial role in structuring microbial communities and regulating nutrient and organic matter flux. Here, we show that the impact on viral density by heterotrophic flagellates is related to their feeding behaviour (feeding on sedimented particles - Thaumatomonas coloniensis, filter feeding of suspended particles - Salpingoeca sp., and actively searching raptorial feeding - Goniomonas truncata). Phage MS2 was co-incubated with flagellates and the natural bacterial and viral community originating from the same groundwater habitats where the flagellates were isolated. Three complementary assays, i.e. flow cytometry, qPCR and plaque assay, were used for enumeration of total viruses, total MS2 phages, and free and infectious MS2, respectively, to provide insights into the grazing mechanisms of the flagellates on viruses. Phage MS2 was actively removed by the suspension feeders T. coloniensis and Salpingoeca sp. in contrast with the actively raptoriale grazer G. truncata. The decline of viral titre was demonstrated to be caused by ingestion rather than random absorption by both qPCR and locating protein fluorescently labelled MS2 inside the flagellates. Further, we indicate that phages can be used as a minor carbon source for flagellates. Collectively, these data demonstrate that eliminating viruses can be an important function of protists in microbial food webs, carbon cycling and potentially water quality control., (© 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.)

A novel approach based on flow cytometric sorting followed by construction of 18S rRNA clone libraries was used to study the diversity of eukaryotic picophytoplankton of lakes. The composition of eukaryotic picophytoplankton community appeared highly variable in three lakes. Eukaryotic picophytoplankton was dominated by Cryptophyta in the Lake Xuanwu, and was mainly composed of Cryptophyta and Chrysophyta in the Lake Zixia. In the Lake Taihu, four phyla were discovered, including Cryptophyta, Chrysophyta, Bacillariophyta and Chlorophyta. Meanwhile, the diversity of eukaryotic picophytoplankton differed in various lake regions. In the Meiliang Bay, Chrysophyta was the dominant, and the other three phyla were found in the Gonghu Bay. In the central lake, all of those four phyla were discovered, implying this region contained the highest diversity. The canonical correspondence analysis between the diversity of eukaryotic picophytoplankton and environmental factors revealed the concentration of total phosphorus had the highest important impact on the eukaryotic picophytoplankton communities.

Different representative of algae and cyanobacteria were isolated from a freshwater habitat and cultivated in laboratory to compare their photoacclimation capacity when exposed to a wide range of light intensity and to understand if this factor may modify natural community dominance. All species successfully acclimated to all light intensities and the response of phytoplankton to increased light intensity was similar and included a decrease of most photosynthetic pigments accompanied by an increase in photoprotective pigment content relative to Chl a. Most species also decreased their light absorption efficiency on a biovolume basis. This decrease not only resulted in a lower fraction of energy absorbed by the cell, but also to a lower transfer of energy to PSII and PSI. Furthermore, energy funnelled to PSII or PSI was also rearranged in favour of PSII. High light acclimated organisms also corresponded to high non-photochemical quenching and photosynthetic electron transport reduction state and to a low Φ'M. Thus photoacclimation processes work toward reducing the excitation pressure in high light environment through a reduction of light absorption efficiency, but also by lowering conversion efficiency. Interestingly, all species of our study followed that tendency despite being of different functional groups (colonial, flagellated, different sizes) and of different phylogeny demonstrating the great plasticity and adaptation ability of freshwater phytoplankton to their light environment. These adjustments may explain the decoupling between growth rate and photosynthesis observed above photosynthesis light saturation point for all species. Even if some species did reach higher growth rate in our conditions and thus, should dominate in natural environment with respect to light intensity, we cannot exclude that other environmental factors also influence the population dynamic and make the outcome harder to predict.

The old town area of Kaixian county was flooded and showed reservoir characteristics after the water level of Three Gorges Reservoir got 172. 8 m in December 2008. The aquatic ecology and nutritional status of Kaixian drawdown area after water storage are still rarely reported. To understand the current water environment and changes in algal community structure of Kaixian drawdown area after 172.8 m water level, the algal composition, abundance, biomass distribution and changes of its sampling spots including Hanfeng Lake were observed twice during winter storage period in January and December 2009. The trends in phytoplankton community structure were analyzed and the water quality assessment of nutritional status was carried out. The results indicated that 6 phylums, 37 genera, 69 species of phytoplankton in total were identified in the two sampling, and the dominant species were Dinophyta and Cryptophyta. The cell density and biomass in December 2009 were lower than those in January 2009. The evaluation results of algal population structure and pollution indicators showed that the nutrition level of Kaixian drawdown area during the winter storage period was mesotrophic to eutrophic type, while diversity analysis result indicated moderate pollution.

During the recent years, wide varieties of methodologies have been developed up to the level of commercial use to measure photosynthetic electron transport by modulated chlorophyll a-in vivo fluorescence. It is now widely accepted that the ratio between electron transport rates and new biomass (P (Fl)/B (C)) is not fixed and depends on many factors that are also taxonomically variable. In this study, the balance between photon absorption and biomass production has been measured in two phycobilin-containing phototrophs, namely, a cyanobacterium and a cryptophyte, which differ in their antenna organization. It is demonstrated that the different antenna organization exerts influence on the regulation of the primary photosynthetic reaction and the dissipation of excessively absorbed radiation. Although, growth rates and the quantum efficiency of biomass production of both phototrophs were comparable, the ratio P (Fl)/B (C) was twice as high in the cryptophyte in comparison to the cyanobacterium. It is assumed that this discrepancy is because of differences in the metabolic regulation of cell growth. In the cryptophyte, absorbed photosynthetic energy is used to convert assimilated carbon directly into proteins and lipids, whereas in the cyanobacterium, the photosynthetic energy is preferentially stored as carbohydrates.

We investigated the retention of dimethylsulfoniopropionate (DMSP) in phototrophic dinoflagellates arising from mixotrophy by estimating the cellular content of DMSP in Karlodinium veneficum (mixotrophic growth) fed for 7-10 days on either DMSP-rich Amphidinium carterae (phototrophic growth only) or DMSP-poor Teleaulax sp. (phototrophic growth only). In K. veneficum fed on DMSP-poor prey, the cellular content of DMSP remained almost unchanged regardless of the rate of feeding, whereas the cellular content of DMSP in cells of K. veneficum fed on DMSP-rich prey increased by as much as 21 times the cellular concentration derived exclusively from phototrophic growth. In both cases, significant fractions (10-32% in the former case and 55-65% in the latter) of the total DMSP ingested by K. veneficum were transformed into dimethylsulfide and other biochemical compounds. The results may indicate that the DMSP content of prey species affects temporal variations in the cellular DMSP content of mixotrophic dinoflagellates, and that mixotrophic dinoflagellates produce DMS through grazing on DMSP-rich preys. Additional studies should be performed to examine the universality of our finding in other mixotrophic dinoflagellates feeding on diverse prey species., (© 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.)

We provide here the description of a new marine species that harbors green or red chloroplasts. In contrast to certain other species of the genus, Mesodinium chamaeleon n. sp. can be maintained in culture for short periods only. It captures and ingests flagellates including cryptomonads. The prey is ingested very rapidly into a food vacuole without the cryptomonad flagella being shed and the trichocysts being discharged. The individual food vacuoles subsequently serve as photosynthetic units, each containing the cryptomonad chloroplast, a nucleus, and some mitochondria. The ingested cells are eventually digested. This type of symbiosis differs from other plastid-bearing Mesodinium spp. in retaining ingested cryptomonad cells almost intact. The food strategy of the new species appears to be intermediate between heterotrophic species, such as Mesodinium pulex and Mesodinium pupula, and species with red cryptomonad endosymbionts, such as Mesodinium rubrum., (© 2011 The Author(s) Journal of Eukaryotic Microbiology © 2011 International Society of Protistologists.)

Grazing mortality of the marine phytoplankton Synechococcus is dominated by planktonic protists, yet rates of consumption and factors regulating grazer-Synechococcus interactions are poorly understood. One aspect of predator-prey interactions for which little is known are the mechanisms by which Synechococcus avoids or resists predation and, in turn, how this relates to the ability of Synechococcus to support growth of protist grazer populations. Grazing experiments conducted with the raptorial dinoflagellate Oxyrrhis marina and phylogenetically diverse Synechococcus isolates (strains WH8102, CC9605, CC9311, and CC9902) revealed marked differences in grazing rates-specifically that WH8102 was grazed at significantly lower rates than all other isolates. Additional experiments using the heterotrophic nanoflagellate Goniomonas pacifica and the filter-feeding tintinnid ciliate Eutintinnis sp. revealed that this pattern in grazing susceptibility among the isolates transcended feeding guilds and grazer taxon. Synechococcus cell size, elemental ratios, and motility were not able to explain differences in grazing rates, indicating that other features play a primary role in grazing resistance. Growth of heterotrophic protists was poorly coupled to prey ingestion and was influenced by the strain of Synechococcus being consumed. Although Synechococcus was generally a poor-quality food source, it tended to support higher growth and survival of G. pacifica and O. marina relative to Eutintinnis sp., indicating that suitability of Synechococcus varies among grazer taxa and may be a more suitable food source for the smaller protist grazers. This work has developed tractable model systems for further studies of grazer-Synechococcus interactions in marine microbial food webs.

Nutritional imbalances between predator and prey are the rule rather than the exception at the lower end of food webs. We investigated the role of different grazers in the propagation of nutritionally imbalanced primary production by using the same primary producers in a three-trophic-level food chain and a four-trophic-level food chain experimental setup. The three-trophic-level food chain consisted of a classic single-cell primary producer (Rhodomonas salina), a metazoan grazer (the copepod Acartia tonsa) and a top predator (the jellyfish Gonionemus vertens), while we added a protozoan grazer (Oxyrrhis marina) as primary consumer to the food chain to establish the four-trophic-level food chain. This setup allowed us to investigate how nutrient-limitation effects change from one trophic level to another, and to investigate the performance of two components of our experimental food chains in different trophic positions. Stoichiometry and fatty acid profiles of the algae showed significant differences between the nutrient-depleted [no N and no P addition (-P), respectively] and the nutrient-replete (f/2) treatments. The differences in stoichiometry could be traced when O. marina was the first consumer. Copepods feeding on these flagellates were not affected by the nutritional imbalance of their prey in their stoichiometry, their respiration rates nor in their developmental rates. In contrast, when copepods were the primary consumer, those reared on the -P algae showed significantly higher respiration rates along with significantly lower developmental rates. In neither of our two experimental food chains did the signals from the base of the food chains travel up to jelly fish, our top predator.

Two strictly aerobic, Gram-negative, rod-shaped bacteria containing photosynthesis-related genes, designated strains CL-SK44(T) and CL-JM1(T), were isolated from a culture of the marine phytoplankton Cryptomonas sp. and coastal seawater from Korea, respectively. Phylogenetic analysis of 16S rRNA gene sequences revealed that the two strains were related to members of the genera Thalassobius (95.3-96.7 % similarity), Pelagibaca (95.3-96.0 %) and Donghicola (95.6 %) in the family Rhodobacteraceae. However, the two novel strains did not form a robust clade with any species of the Roseobacter clade, forming a distinct clade. The major polar lipids of the strains were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, an unidentified aminolipid and an unidentified lipid, profiles that were distinguishable from those of the related genera examined. Although the level of 16S rRNA gene sequence similarity between strains CL-SK44(T) and CL-JM1(T) was very high (99.1 %), DNA-DNA relatedness between the strains was 13 %, suggesting that they represent genomically distinct species. In addition, the two strains could be differentiated based on the presence of a minor polar lipid, on the hydrolysis of gelatin and the utilization of carbon sources. Based on the data from the present study, strains CL-SK44(T) and CL-JM1(T) are considered to represent separate novel species of a new genus of the family Rhodobacteraceae, for which the names Marivita cryptomonadis gen. nov., sp. nov. (type species) and Marivita litorea sp. nov. are proposed. The type strains of Marivita cryptomonadis and Marivita litorea are CL-SK44(T) (=KCCM 90070(T)=JCM 15447(T)) and CL-JM1(T) (=KCCM 90071(T)=JCM 15446(T)), respectively.

We study the effects of toxicants on the functioning of phototrophic unicellular organism (an algae) in a simple aquatic microcosm by applying a parameter-sparse model. The model allows us to study the interaction between ecological and toxicological effects. Nutrient stress and toxicant stress, together or alone, can cause extinction of the algal population. The modelled algae consume dissolved inorganic nitrogen (DIN) under surplus light and use it for growth and maintenance. Dead algal biomass is mineralized by bacterial activity, leading to nutrient recycling. The ecological model is coupled with a toxicity-module that describes the dependency of the algal growth and death rate on the toxicant concentration. Model parameter fitting is performed on experimental data from Liebig, M., Schmidt, G., Bontje, D., Kooi, B.W., Streck, G., Traunspurger, W., Knacker, T. [2008. Direct and indirect effects of pollutants on algae and algivorous ciliates in an aquatic indoor microcosm. Aquatic Toxicology 88, 102-110]. These experiments were especially designed to include nutrient limitation, nutrient recycling and long-term exposure to toxicants. The flagellate species Cryptomonas sp. was exposed to the herbicide prometryn and insecticide methyl parathion in semi-closed Erlenmeyers. Given the total limiting amount of nitrogen in the system, the estimated toxicant concentration at which a long-term steady population of algae goes extinct will be derived. We intend to use the results of this study to investigate the effects of ecological (environmental) and toxicological stresses on more realistic ecosystem structure and functioning.

Thylakoid membranes of the cryptophyte Chroomonas sp. strain LT were solubilized with dodecyl-beta-maltoside and subjected to sucrose density gradient centrifugation. The four pigment protein complexes obtained were subsequently characterized by absorption and fluorescence spectroscopy, SDS-PAGE, and Western immunoblotting using antisera against the chlorophyll a/c-binding proteins of the marine cryptophyte Cryptomonas maculata and the reaction-center protein D2 of photosystem II of maize. Band 1 consisted mainly of free pigments, phycobiliproteins, and chlorophyll-a/c-binding proteins. Band 2 represented a major chlorophyll a/c-binding protein fraction. A mixture of photosystem II and photosystem I proteins comprised band 3, whereas band 4 was enriched in proteins of photosystem I. Western immunoblotting demonstrated the presence of chlorophyll a/c-binding proteins and their association with photosystem I in band 4. Phosphorylation experiments showed that chlorophyll a/c-binding proteins became phosphorylated. Negative staining electron microscopy of band B4 revealed photosystem I particles with dimensions of 22 nm. Our work showed that PSI-LHCI complexes of cryptophytes are similar to those of Chlamydomonas rheinhardtii, the diatom Phaeodactylum tricornutum, and higher plants.

An aquatic indoor microcosm was used to study effects of the pesticides parathion-methyl and prometryn on phototrophic flagellates (Cryptomonas sp.) and predatory ciliates (Urotricha furcata). Parathion-methyl caused effects to flagellates and ciliates at the range of low mg L(-1), regardless of whether the organisms were exposed separately or combined in the multi-species test system. Prometryn caused effects on the flagellates at low microg L(-1) concentrations, resulting in a NOEC of 6.9 microg L(-1) in the single-species test and a NOEC of 15.2 microg L(-1) in the multi-species microcosm. For ciliates the NOEC decreased by factor 145 in the multi-species test compared to the NOEC of 2.2 mg L(-1) in the single-species test when exposed to prometryn. The lower NOEC for ciliates exposed to prometryn in the microcosm was most likely caused by an indirect effect due to reduced availability of flagellates as food. The measurement of nutrient concentrations in the test media and organisms facilitated the modelling of effects. The presented aquatic indoor microcosm is considered as a tool which could be standardised and applied as an instrument to provide data for higher tier risk assessment.

Phototrophic chromalveolates possess plastids surrounded by either 3 or 4 membranes, revealing their secondary endosymbiotic origin from an engulfed eukaryotic alga. In cryptophytes, a member of the chromalveolates, the organelle is embedded within a designated region of the host's rough endoplasmic reticulum (RER). Its eukaryotic compartments other than the plastid were reduced to the mere remains of its former cytosol, the periplastid compartment (PPC, PP space), and its nucleus, the nucleomorph, separated from the RER by its former plasma membrane, the periplast membrane (PPM). In the nucleomorph genome of the cryptophyte Guillardia theta, we identified several genes sharing homology with components of the ER-associated degradation (ERAD) machinery of yeast and higher eukaryotes, namely ORF201 and ORF477, homologs of membrane-bound proteins, Der1p (Degradation in the ER protein 1) and the RING-finger ubiquitin ligase Hrd1, and a truncated version of Udf1, a cofactor of Cdc48, a lumenal ATPase. Exemplarily, studies on the Der1-homolog ORF201 showed that this protein partially rescued a yeast deletion mutant, indicating the existence of a functional PPC-specific ERAD-like system in cryptophytes. With the noninvestigated exception of haptophytes a phylogenetically and mechanistically related system is apparently present in all chromalveolates with 4 membrane-bound plastids because amongst others, PPC-specific Derlins (Der1-like proteins), CDC48 and its cofactor Ufd1 were identified in the nuclear genomes of diatoms and apicomplexa. These proteins are equipped with the required topogenic signals to direct them into the periplastid compartment of their secondary symbionts. Based on our findings, we suggest that all chromalveolates with 4 membrane-bound plastids express an ERAD-derived machinery in the PPM of their secondary plastid, coexisting physically and systematically adjacent to the host's own ERAD system. We propose herewith that this system was functionally adapted to mediate transport of nucleus-encoded PPC/plastid preproteins from the RER into the periplastid space.

The Abraham solvation parameter model is used to construct mathematical correlations for describing the nonspecific toxicity of organic compounds to three protozoas (Entosiphon sulcantum, Uronema parduczi and Chilomonas paramecium). The derived mathematical correlations describe the observed published toxicity data to within an overall average standard deviation of approximately 0.35 log units. The correlations can be used to estimate aquatic toxicities of organic chemicals to the three aquatic organisms studied, and to help in identifying compounds whose toxic mode of action might involve chemical specific reactivity, rather than nonpolar or polar narcosis. A principal component analysis of the correlation equations found in this work shows that no water-solvent system we have investigated is a good model for nonspecific aquatic toxicity towards the three protozoas. Furthermore, correlation equations for nonspecific aqueous toxicity towards various biological systems, that we have found in this work and in previous studies, cover such a wide range that no single water-solvent system could ever be a good model for all the biological systems.

Partitioning of CO(2) incorporation into oxygenic phototrophic, anoxygenic phototrophic, and chemolithoautotrophic guilds was determined in a freshwater lake (Lake Cisó, Banyoles, Spain). CO(2) incorporation into the different types of microorganisms was studied at different depths, during diel cycles, and throughout the year. During winter holomixis, the whole lake became anoxic and both the anoxygenic and chemolithoautotrophic guilds were more active at the surface of the lake, whereas the activity of the oxygenic guild was negligible. During stratification, the latter guild was more active in the upper metalimnion, whereas the anoxygenic guild was more active in the lower metalimnion. Specific growth rates and doubling times were estimated for the most conspicuous phototrophic microorganisms. Doubling times for Cryptomonas phaseolus ranged between 0.5 and 192 days, whereas purple sulfur bacteria (Chromatiaceae-like) ranged between 1.5 and 238 days. These growth rates were similar to those calculated with a different approach in previous papers and indicate slow-growing populations with very large biomass. Overall, the annual total CO(2) incorporation in Lake Cisó was 220 g C m(-2). Most of the CO(2) incorporation, however, was due to the chemolithoautotrophic guild (61% during holomixis and 56% during stratification), followed by the anoxygenic phototrophic guild (35 and 19%, respectively) and the oxygenic phototrophs (4 and 25%, respectively), making dark carbon fixation the key process in the autotrophic metabolism of the lake.