Photosynthate partitioning in cultured marine phytoplankton: metabolic patterns in a marine diatom under constant and variable light intensities

Reactive oxygen species (ROS) like superoxide drive rapid transformations of carbon and metals in aquatic systems and play dynamic roles in biological health, signaling, and defense across a diversity of cell types. In phytoplankton, however, the ecophysiological role(s) of extracellular superoxide production has remained elusive. Here, the mechanism and function of extracellular superoxide production by the marine diatom Thalassiosira oceanica are described. Extracellular superoxide production in T. oceanica exudates was coupled to the oxidation of NADPH. A putative NADPH-oxidizing flavoenzyme with predicted transmembrane domains and high sequence similarity to glutathione reductase (GR) was implicated in this process. GR was also linked to extracellular superoxide production by whole cells via quenching by the flavoenzyme inhibitor diphenylene iodonium (DPI) and oxidized glutathione, the preferred electron acceptor of GR. Extracellular superoxide production followed a typical photosynthesis-irradiance curve and increased by 30% above the saturation irradiance of photosynthesis, while DPI significantly impaired the efficiency of photosystem II under a wide range of light levels. Together, these results suggest that extracellular superoxide production is a byproduct of a transplasma membrane electron transport system that serves to balance the cellular redox state through the recycling of photosynthetic NADPH. This photoprotective function may be widespread, consistent with the presence of putative homologs to T. oceanica GR in other representative marine phytoplankton and ocean metagenomes. Given predicted climate-driven shifts in global surface ocean light regimes and phytoplankton community-level photoacclimation, these results provide implications for future ocean redox balance, ecological functioning, and coupled biogeochemical transformations of carbon and metals.

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On the use of antibiotics for isolating bacteria-free cultures of marine phytoplankton organisms

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400003714 ◽

1952 ◽

Vol 31 (1) ◽

pp. 97-106 ◽

Cited By ~ 48

Author(s):

C. P. Spencer

Keyword(s):

Fresh Water ◽

Solid Medium ◽

Classical Method ◽

Single Cells ◽

Marine Phytoplankton ◽

Marine Diatom ◽

Sterile Medium ◽

Kinetics Of ◽

Water Species ◽

Algal Cultures

In the course of some studies on the kinetics of growth and the biochemical activities of a marine diatom it became desirable to obtain bacteria-free cultures. The classical method of obtaining such pure algal cultures involves either repeatedly washing single cells in sterile medium or obtaining discrete bacteria-free algal colonies by growth on a solid medium. Both these methods have been widely applied to fresh-water species by Pringsheim (1946) and others, whilst Chu (1946) has used both methods with the marine diatom Nitzschia closterium (Ehrenberg) Wm. Smith forma minutissima.

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Ultraviolet radiation stimulated activity of extracellular carbonic anhydrase in the marine diatom Skeletonema costatum

Functional Plant Biology ◽

10.1071/fp08172 ◽

2009 ◽

Vol 36 (2) ◽

pp. 137 ◽

Cited By ~ 27

Author(s):

Hongyan Wu ◽

Kunshan Gao

Keyword(s):

Carbonic Anhydrase ◽

Ultraviolet Radiation ◽

Uv Radiation ◽

Carbon Fixation ◽

Skeletonema Costatum ◽

Marine Phytoplankton ◽

Marine Diatom ◽

Redox Activity ◽

Photosynthetic Carbon Fixation ◽

Photosynthetic Carbon

Previous studies have shown that reduced levels of solar UV radiation (280–400 nm) can enhance photosynthetic carbon fixation of marine phytoplankton, but the mechanisms are not known. The supply of CO2 for photosynthesis is facilitated by extracellular (periplasmic) carbonic anhydrase (CAe) in most marine phytoplankton species. The present study showed that the CAe activity of Skeletonema costatum (Greville) Cleve was stimulated when treated with UV-A (320–395 nm) or UV-A + UV-B (295–320 nm) in addition to visible radiation. The presence of UV-A and UV-B enhanced the activity by 28% and 24%, respectively, at a low irradiance (PAR 161, UV-A 28, UV-B 0.9 W m−2) and by 21% and 19%, respectively, at a high irradiance (PAR 328, UV-A 58, UV-B 1.9 W m−2) level after exposure for 1 h. Ultraviolet radiation stimulated CAe activity contributed up to 6% of the photosynthetic carbon fixation as a result of the enhanced supply of CO2, as revealed using the CAe inhibitor (acetazolamide). As a result, there was less inhibition of photosynthetic carbon fixation compared with the apparent quantum yield of PSII. The UV radiation stimulated CAe activity coincided with the enhanced redox activity at the plasma membrane in the presence of UV-A and/or UV-B. The present study showed that UV radiation can enhance CAe activity, which plays an important role in counteracting UV inhibition of photosynthesis.

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Polycyclovorans algicola gen. nov., sp. nov., an Aromatic-Hydrocarbon-Degrading Marine Bacterium Found Associated with Laboratory Cultures of Marine Phytoplankton

Applied and Environmental Microbiology ◽

10.1128/aem.02833-12 ◽

2012 ◽

Vol 79 (1) ◽

pp. 205-214 ◽

Cited By ~ 52

Author(s):

Tony Gutierrez ◽

David H. Green ◽

Peter D. Nichols ◽

William B. Whitman ◽

Kirk T. Semple ◽

...

Keyword(s):

16S Rrna ◽

16S Rrna Gene ◽

Aromatic Hydrocarbon ◽

Skeletonema Costatum ◽

Marine Phytoplankton ◽

Marine Diatom ◽

Rrna Gene ◽

Strictly Aerobic ◽

Content Type ◽

Degrading Bacteria

ABSTRACTA strictly aerobic, halotolerant, rod-shaped bacterium, designated strain TG408, was isolated from a laboratory culture of the marine diatomSkeletonema costatum(CCAP1077/1C) by enrichment with polycyclic aromatic hydrocarbons (PAHs) as the sole carbon source. 16S rRNA gene sequence analysis placed this organism within the orderXanthomonadalesof the classGammaproteobacteria. Its closest relatives included representatives of theHydrocarboniphaga-Nevskia-Sinobacterclade (<92% sequence similarity) in the familySinobacteraceae. The strain exhibited a narrow nutritional spectrum, preferring to utilize aliphatic and aromatic hydrocarbon compounds and small organic acids. Notably, it displayed versatility in degrading two- and three-ring PAHs. Moreover, catechol 2,3-dioxygenase activity was detected in lysates, indicating that this strain utilizes themeta-cleavage pathway for aromatic compound degradation. Cells produced surface blebs and contained a single polar flagellum. The predominant isoprenoid quinone of strain TG408 was Q-8, and the dominant fatty acids were C16:0, C16:1ω7c, and C18:1ω7c. The G+C content of the isolate's DNA was 64.3 mol% ± 0.34 mol%. On the basis of distinct phenotypic and genotypic characteristics, strain TG408 represents a novel genus and species in the classGammaproteobacteriafor which the namePolycyclovorans algicolagen. nov., sp. nov., is proposed. Quantitative PCR primers targeting the 16S rRNA gene of this strain were developed and used to show that this organism is found associated with other species of marine phytoplankton. Phytoplankton may be a natural biotope in the ocean where new species of hydrocarbon-degrading bacteria await discovery and which contribute significantly to natural remediation processes.

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Marine Phytoplankton Photosynthesis as a Function of Light Intensity: A Comparison of Methods

Journal of the Fisheries Research Board of Canada ◽

10.1139/f64-013 ◽

1964 ◽

Vol 21 (1) ◽

pp. 159-181 ◽

Cited By ~ 103

Author(s):

C. D. McAllister ◽

N. Shah ◽

J. D. H. Strickland

Keyword(s):

Cell Division ◽

Skeletonema Costatum ◽

Algal Growth ◽

Net Photosynthesis ◽

Growth Conditions ◽

Marine Phytoplankton ◽

Fluorescent Light ◽

Particulate Carbon ◽

Gross Photosynthesis ◽

Light Intensities

An apparatus is described in which the constant for exponential algal growth has been determined as a function of light at controlled temperature. Studies were made of bacteria-free cultures of Skeletonema costatum and Dunaliella tertiolecta grown at the optimum temperature for cell division in media with and without adequate nitrate and phosphate. Less complete studies were made of the behaviour of Monochrysis lutheri and Amphidinium carteri. In all experiments the growth constants were determined at known light intensities, expressed in the energy units, langlies/minute, using light of a known spectral distribution similar to sunlight shining through a few metres of coastal sea water.Growth constants were determined for the following processes: increase of cellular carbon, chlorophylls a, b or c, carotenoids, cell numbers and photosynthesis measured both by oxygen evolution (net and gross) and by the uptake of C-14 labelled carbonate.The rate of maximum photosynthesis occurred when the illumination reached about 0.1 ly/min and little or no light inhibition occurred when the intensity was increased to as high as 0.4 ly/min. Respiration was about 10% of maximum gross photosynthesis. This fraction increased when cells were nitrogen deficient but decreased in phosphate deficient cultures because a phosphate shortage inhibited respiration more severely than photosynthesis.Gross photosynthesis at low light intensities was proportional to the total number of molecules of all plant pigments added together, irrespective of species or of culturing conditions. By contrast, the rate of maximum gross photosynthesis was poorly related to pigment composition, the best correspondence being with the amount of chlorophyll a in the cultures.The uptake rate of C-14 varied with time. There was an apparent "leakage" of labelled organic matter which eventually reached a near-equilibrium with 14CO2 uptake, after which the C-14 method measured the production of particulate carbon but not necessarily net or gross photosynthesis. The rate of particulate carbon production was the same as that of cell division but about 40% less than net photosynthesis in cultures of Skeletonema. Agreement between C-14 rates and net photosynthesis was better in cool-white fluorescent light than in the imitation submarine sunlight used in this work. At high light intensities there was apparently no excretion from Dunaliella "shade" cells but when these became changed to "sun" cells they behaved more like Skeletonema.Various observations are recorded of the effect of growth conditions on cell composition, especially with regard to pigments.The relatively low C-14 rates found with Skeletonema costatum may be explicable in part by an abnormally low counting efficiency for this species even when present as a "weightless" source but the problem requires further study.

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Interaction of a dinoflagellate neurotoxin with voltage-activated ion channels in a marine diatom

PeerJ ◽

10.7717/peerj.4533 ◽

2018 ◽

Vol 6 ◽

pp. e4533 ◽

Cited By ~ 1

Author(s):

Sheila A. Kitchen ◽

Andrea J. Bourdelais ◽

Alison R. Taylor

Keyword(s):

Action Potential ◽

Binding Site ◽

Action Potentials ◽

Harmful Algal Bloom ◽

Single Domain ◽

Marine Phytoplankton ◽

Marine Diatom ◽

Membrane Excitability ◽

Voltage Gated ◽

Kinetics Of

Background The potent neurotoxins produced by the harmful algal bloom species Karenia brevis are activators of sodium voltage-gated channels (VGC) in animals, resulting in altered channel kinetics and membrane hyperexcitability. Recent biophysical and genomic evidence supports widespread presence of homologous sodium (Na+) and calcium (Ca2+) permeable VGCs in unicellular algae, including marine phytoplankton. We therefore hypothesized that VGCs of these phytoplankton may be an allelopathic target for waterborne neurotoxins produced by K. brevis blooms that could lead to ion channel dysfunction and disruption of signaling in a similar manner to animal Na+ VGCs. Methods We examined the interaction of brevetoxin-3 (PbTx-3), a K. brevis neurotoxin, with the Na+/Ca2+ VGC of the non-toxic diatom Odontella sinensis using electrophysiology. Single electrode current- and voltage- clamp recordings from O. sinensis in the presence of PbTx-3 were used to examine the toxin’s effect on voltage gated Na+/Ca2+ currents. In silico analysis was used to identify the putative PbTx binding site in the diatoms. We identified Na+/Ca2+ VCG homologs from the transcriptomes and genomes of 12 diatoms, including three transcripts from O. sinensis and aligned them with site-5 of Na+ VGCs, previously identified as the PbTx binding site in animals. Results Up to 1 µM PbTx had no effect on diatom resting membrane potential or membrane excitability. The kinetics of fast inward Na+/Ca2+ currents that underlie diatom action potentials were also unaffected. However, the peak inward current was inhibited by 33%, delayed outward current was inhibited by 25%, and reversal potential of the currents shifted positive, indicating a change in permeability of the underlying channels. Sequence analysis showed a lack of conservation of the PbTx binding site in diatom VGC homologs, many of which share molecular features more similar to single-domain bacterial Na+/Ca2+ VGCs than the 4-domain eukaryote channels. Discussion Although membrane excitability and the kinetics of action potential currents were unaffected, the permeation of the channels underlying the diatom action potential was significantly altered in the presence of PbTx-3. However, at environmentally relevant concentrations the effects of PbTx- on diatom voltage activated currents and interference of cell signaling through this pathway may be limited. The relative insensitivity of phytoplankton VGCs may be due to divergence of site-5 (the putative PbTx binding site), and in some cases, such as O. sinensis, resistance to toxin effects may be because of evolutionary loss of the 4-domain eukaryote channel, while retaining a single domain bacterial-like VGC that can substitute in the generation of fast action potentials.

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Responses of Marine Diatom-Dinoflagellate Competition to Multiple Environmental Drivers: Abundance, Elemental, and Biochemical Aspects

Frontiers in Microbiology ◽

10.3389/fmicb.2021.731786 ◽

2021 ◽

Vol 12 ◽

Author(s):

Rong Bi ◽

Zhong Cao ◽

Stefanie M. H. Ismar-Rebitz ◽

Ulrich Sommer ◽

Hailong Zhang ◽

...

Keyword(s):

Chemical Composition ◽

Algal Blooms ◽

Phytoplankton Community ◽

Additive Models ◽

Prorocentrum Minimum ◽

Marine Phytoplankton ◽

Marine Diatom ◽

Environmental Drivers ◽

Nutrient Concentrations ◽

High Nutrient

Ocean-related global change has strongly affected the competition between key marine phytoplankton groups, such as diatoms and dinoflagellates, especially with the deleterious consequency of the increasing occurrence of harmful algal blooms. The dominance of diatoms generally shifts toward that of dinoflagellates in response to increasing temperature and reduced nutrient availability; however, contradictory findings have also been observed in certain sea areas. A key challenge in ecology and biogeochemistry is to quantitatively determine the effects of multiple environmental factors on the diatom-dinoflagellate community and the related changes in elemental and biochemical composition. Here, we test the interplay between temperature, nutrient concentrations and their ratios on marine diatom-dinoflagellate competition and chemical composition using bi-algal competition experiments. The ubiquitous diatom Phaeodactylum tricornutum and dinoflagellate Prorocentrum minimum were cultivated semi-continuously, provided with different N and P concentrations (three different levels) and ratios (10:1, 24:1, and 63:1 molar ratios) under three temperatures (12, 18, and 24°C). The responses of diatom-dinoflagellate competition were analyzed by a Lotka-Volterra model and quantified by generalized linear mixed models (GLMMs) and generalized additive models (GAMs). The changes in nutrient concentrations significantly affected diatom-dinoflagellate competition, causing a competitive superiority of the diatoms at high nutrient concentrations, independent of temperature and N:P supply ratios. Interestingly, the effect amplitude of nutrient concentrations varied with different temperatures, showing a switch back toward a competitive superiority of the dinoflagellates at the highest temperature and at very high nutrient concentrations. The ratios of particulate organic nitrogen to phosphorus showed significant negative correlations with increasing diatoms/dinoflagellates ratios, while lipid biomarkers (fatty acids and sterols) correlated positively with increasing diatoms/dinoflagellates ratios over the entire ranges of temperature, N and P concentrations and N:P ratios. Our results indicate that the integration of phytoplankton community structure and chemical composition provides an important step forward to quantitatively understand and predict how phytoplankton community changes affect ecosystem functions and biogeochemical cycles in the ocean.

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Studies on the Factors Affecting the Release of Organic Matter By Skeletonema Costatum (Greville) Cleve in Culture

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400022591 ◽

1973 ◽

Vol 53 (4) ◽

pp. 937-956 ◽

Cited By ~ 62

Author(s):

L. Ignatiades ◽

G. E. Fogg

Keyword(s):

Organic Matter ◽

Skeletonema Costatum ◽

Physiological Activity ◽

Marine Phytoplankton ◽

Low Light ◽

Factors Affecting ◽

Light Intensities

A few studies on the excretion of organic matter by marine phytoplankton in culture have been reported (Guillard & Wangersky, 1958; Wangersky & Guillard, 1960; Stewart, 1963; Hellebust, 1965). Eppley & Sloan (1965) reported extensive excretion in Skeletonema costatum (Greville) Cleve cultures as they approached senescence and emphasized that excretion is inversely proportional to the physiological activity of cells. Hellebust (1965) demonstrated the release of high amounts (up to 38% of the carbon assimilated) of organic matter by Sk. costatum cells exposed to low light intensities. It is apparent that more knowledge is needed in order to define the intra- and extracellular factors affecting the excretion.

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Influence of the carbon concentrating mechanism on carbon stable isotope discrimination by the marine diatom Thalassiosira pseudonana

Canadian Journal of Botany ◽

10.1139/b98-069 ◽

1998 ◽

Vol 76 (6) ◽

pp. 1098-1103 ◽

Cited By ~ 4

Author(s):

Anthony S Fielding ◽

David H Turpin ◽

Robert D Guy ◽

Stephen E Calvert ◽

David W Crawford ◽

...

Keyword(s):

Carbon Isotope ◽

Inorganic Carbon ◽

Carbon Isotope Discrimination ◽

Thalassiosira Pseudonana ◽

Marine Phytoplankton ◽

Marine Diatom ◽

Carbon Concentrating Mechanism ◽

Fractionation Factor ◽

Isotope Discrimination ◽

Concentrating Mechanism

There is no clear explanation why phytoplankton δ13C values are more negative in colder waters, but one current theory suggests that because colder waters hold more CO2, there is less diffusional limitation of CO2. This results in more discrimination against 13C and more negative phytoplankton δ13Cvalues. However, many species are able to actively take up CO2 or HCO3-, the latter being the major inorganic carbon species present in the dissolved inorganic carbon (DIC) pool of modern oceans. A previous study suggests that carbon concentrating mechanism (CCM) induction would affect carbon isotope discrimination, and this study confirms the presence of a relationship between discrimination and induction of a CCM in the marine diatom Thalassiosira pseudonana. CCM induction was measured by determining the half-saturation constant of photosynthesis (K0.5DIC). Values of K0.5DIC increased from 85 to 470 m M DIC over a range of ambient DIC levels from 0.2 to 2.7 mM. The fractionation factor increased from 10 to 21.3omicron over this same range. There was a significant relationship between K0.5DIC and the fractionation factor suggesting that CCM induction state influences carbon isotope discrimination. Other factors that influence discrimination may act through CCM induction.Key words: carbon isotope discrimination, carbon concentrating mechanism, Thalassiosira pseudonana, active carbon uptake, marine phytoplankton.

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