Diatom Phaeodactylum Tricornutum Bohlin Research Articles

Can BPA Analogs Affect Cellular and Biochemical Responses in the Microalga Phaeodactylum tricornutum Bohlin?

Bisphenol A analogs (BPA analogs) are emerging contaminants with a rising production caused by the replacement of BPA with these compounds. The increased production of BPA analogs is leading to their increased release into various ecosystems, including marine ones. The aim of this study was to evaluate the biological effects of BPA analogs on a primary producer, the diatom Phaeodactylum tricornutum Bohlin. Three different BPA analogs (BPAF, BPF, and BPS) and their mixture were tested at the environmental relevant concentration of 300 ng/L. Growth, cell size and several biomarkers of oxidative stress and oxidative damage were measured. Our results indicated that the tested compounds caused a reduced growth rate and induced oxidative stress, altering many antioxidant enzymes in P. tricornutum. However, no oxidative damages were observed.

Experimental determination of concentration factors of Ni, Ru and Sb in the model diatom Phaeodactylum tricornutum

This paper describes the experimental determination of concentration factors (CF) for nickel, ruthenium and antimony in the model diatom Phaeodactylum tricornutum Bohlin (Bacillariophyceae), which was chosen as a representative of marine phytoplankton. Better determinations of these CF are needed to improve the modelling of marine ecosystems at release points, where radioactive pollutants enter the ecosystem, for more accurate predictions of radiation dose to humans caused by these pollutants. A literature study revealed that the currently implemented values of these CF are based on very scarce data, and a computational sensitivity study showed that the radiation dose caused by radioisotopes of these elements depend strongly on the phytoplankton CF. Nutrient-enriched water samples from Swedish coastal waters were used as a medium for growing of the diatom species P. tricornutum and radioactive isotopes of the studied elements were added to the cultures during the exponential growth phase. The radioactivity in the P. tricornutum and in the culture medium were measured separately and used for determination of CF. Conservative estimates of the CF based on this phytoplankton proxy on the present data are 6400 L/kg for nickel, 20,000 L/kg for ruthenium and 890 L/kg for antimony, with P. tricornutum biomass masses referring to dry weight. The estimates for nickel and ruthenium are similar to previously published values, which underpins the credibility of radiation dose calculations based on these values. The estimate for antimony is uncertain, but also, to our knowledge, represents the first published experimentally based data on this CF.

Wake-Riding Effect-Inspired Opto-Hydrodynamic Diatombot for Non-Invasive Trapping and Removal of Nano-Biothreats.

Contamination of nano-biothreats, such as viruses, mycoplasmas, and pathogenic bacteria, is widespread in cell cultures and greatly threatens many cell-based bio-analysis and biomanufacturing. However, non-invasive trapping and removal of such biothreats during cell culturing, particularly many precious cells, is of great challenge. Here, inspired by the wake-riding effect, a biocompatible opto-hydrodynamic diatombot (OHD) based on optical trapping navigated rotational diatom (Phaeodactylum tricornutum Bohlin) for non-invasive trapping and removal of nano-biothreats is reported. Combining the opto-hydrodynamic effect and optical trapping, this rotational OHD enables the trapping of bio-targets down to sub-100nm. Different nano-biothreats, such as adenoviruses, pathogenic bacteria, and mycoplasmas, are first demonstrated to be effectively trapped and removed by the OHD, without affecting culturing cells including precious cells such as hippocampal neurons. The removal efficiency is greatly enhanced via reconfigurable OHD array construction. Importantly, these OHDs show remarkable antibacterial capability, and further facilitate targeted gene delivery. This OHD serves as a smart micro-robotic platform for effective trapping and active removal of nano-biothreats in bio-microenvironments, and especially for cell culturing of many precious cells, with great promises for benefiting cell-based bio-analysis and biomanufacturing.

Response of marine microalgae Phaeodactylum tricornutum, Prorocentrum cordatum and Gyrodinium fissum to complex pollution of Sevastopol bays (Black Sea)

For the degrees of toxicity assessment within the Black Sea surface coastal waters near Sevastopol, laboratory experiments were performed on three marine microalgae species culture’s growth in water sampled on the three stations of the region from May to December 2020. The study has indicated, that in the majority of cases, insignificant inhibiting influences of the waters to diatom Phaeodactylum tricornutum Bohlin and insignificant stimulated effect to dinoflagellates Prorocentrum сordatum (Ostenfeld) J.D.Dodge and Gyrodinium fissum (Levander) Kofoid & Swezy were observed. Rarely this effect was characterized as chronic or subacute. The concentration levels of both stable and unstable forms of organic substances in the studied waters were estimated. The results of the testing of the water to determine its contamination using microalgae and analysis of the organic substances concentration levels in them, allowed the conclusion that the studied area should be classified as episodically polluted. Justification for the necessity to use several microalgae species of different taxonomic affiliation when performing marine water biotesting is provided in this study.

Hormesis-like growth and photosynthetic physiology of marine diatom Phaeodactylum tricornutum Bohlin exposed to polystyrene microplastics

Hormesis-like growth and photosynthetic physiology of marine diatom Phaeodactylum tricornutum Bohlin exposed to polystyrene microplastics

The stresses of allelochemicals isolated from culture solution of diatom Phaeodactylum tricornutum Bohlin on growth and physiology of two marine algae

The allelopathic effects of extracts isolated from the culture filtrate of diatom Phaeodactylum triconutum Bohlin on typical marine microalgae Prorocentrum donghaiense Lu and Dunaliella salina Teodoresco were investigated by determining different physiological and biochemical parameters, such as growth rate, membrane systems and esterase activity under controlled laboratory conditions. The growth of P. donghaiense was significantly inhibited immediately after exposure to the allelochemicals, while the algae density of D. salina was less sensitive. Chlorophyll-a content, membrane systems, as well as esterase activity were simultaneously investigated by flow cytometry with particular fluorescent markers and exhibited changeable sensitivities. The results demonstrated that the membrane systems of P. donghaiense were suppressed by the allelochemicals directly, causing loss of integrity and membrane penetration. Esterase activity was the most sensitive indicator as that of P. donghaiense cells significantly increased in short time and was inhibited subsequently. However, the membrane of D. salina remained intact still after exposure to the extracts and the esterase activity was only inhibited on last day during experiment period. Membrane potential and chlorophyll-a content of the two marine algae also showed somewhat different changes, as that of P. donghaiense cells were impaired after 5 day exposure to all volume conditions while these two characteristics of D. salina was only suppressed by exposure to high volume of the allelochemicals on day 6. The present results indicated that the inhibition of culture filtrate of P. triconutum on P. donghaiense was algicidal whereas the effect on D. salina appeared to be algistatic.

Pilot-scale production of antibacterial substances by the marine diatom Phaeodactylum tricornutum Bohlin

The production and extraction of antibacterial substances from Phaeodactylum tricornutum biomass were tested on a pilot scale in a photo-bioreactor greenhouse installation. Using column chromatography two antibacterial active fractions were obtained from the algal biomass: a pure fraction of eicosapentaenoic acid (EPA) and a potentially new antibacterial substance(s) (identified as fraction B) produced by P. tricornutum. Both fractions exhibited antibacterial activities against three human pathogens: Vibrio vulnificus, V. parahaemolyticus, and V. cholerae. Minimal inhibitory concentrations against Bacillus subtilis of active fractions and one antibacterial commercial product were determined revealing a higher antibacterial activity of EPA in comparison to the commercial product. Consequently, EPA as well as the raw algal biomass with both EPA and the fraction B compounds could be used as food additives and feeds in aquaculture, poultry, and livestock breeding. Two types of phytohormones, methyl jasmonate and salicylic acid, as well as one phytotoxin, coronatine, were tested for induction of the defense system of P. tricornutum. However, only a minor change in the fatty acids profile and antibacterial effects of the treated cultures indicated that P. tricornutum must employ another strategy to regulate its antibacterial defense system.

Evaluating trace element bioavailability and potential transfer into marine food chains using immobilised diatom model species Phaeodactylum tricornutum, on King George Island, Antarctica

In order to evaluate trace element bioavailability and potential transfer into marine food chains in human impacted areas of the Fildes Peninsula (King George Island, South Shetland Islands Archipelago), element levels (Cr, Ni, Cu, Zn, Cd, and Pb) were determined in water, sediments, phytoplankton, and in diatom Phaeodactylum tricornutum Bohlin (Bacillariophyceae) cells immobilised in alginate and exposed to water and sediments, from the Bellingshausen Dome (reference site) and Ardley Cove (human impacted area), during January 2014. High element concentrations in exposed P. tricornutum indicated element mobilisation from sediments into the water. Levels in exposed cells reflected the sediment element content pattern, comparable to those found in phytoplankton, supporting phytoplankton as an important path of trace element entry into marine food chains. This study clearly shows immobilised P. tricornutum as good proxy of phytoplankton concerning element accumulation efficiency, and an effective tool to monitor trace element contamination in polar coastal ecosystems.

Metabolic flux ratio analysis and cell staining suggest the existence of C4 photosynthesis in Phaeodactylum tricornutum.

Mechanisms for carbon fixation via photosynthesis in the diatom Phaeodactylum tricornutum Bohlin were studied recently but there remains a long-standing debate concerning the occurrence of C4 photosynthesis in this species. A thorough investigation of carbon metabolism and the evidence for C4 photosynthesis based on organelle partitioning was needed. In this study, we identified the flux ratios between C3 and C4 compounds in P. tricornutum using (13)C-labelling metabolic flux ratio analysis, and stained cells with various cell-permeant fluorescent probes to investigate the likely organelle partitioning required for single-cell C4 photosynthesis. Metabolic flux ratio analysis indicated the C3/C4 exchange ratios were high. Cell staining indicated organelle partitioning required for single-cell C4 photosynthesis might exist in P. tricornutum. The results of (13)C-labelling metabolic flux ratio analysis and cell staining suggest single-cell C4 photosynthesis exists in P. tricornutum. This study provides insights into photosynthesis patterns of P. tricornutum and the evidence for C4 photosynthesis based on (13)C-labelling metabolic flux ratio analysis and organelle partitioning.

The dynamics of the intracellular contents of carbon, nitrogen, and chlorophyll a under conditions of batch growth of the diatom Phaeodactylum tricornutum (Bohlin, 1897) at different light intensities

It was found that during batch growth of the diatom Phaeodactylum tricornutum (Bohlin, 1897) the specific content of nitrogen in the cells (relative to carbon) decreased with decreasing nitrogen concentration in the medium below ∼10 µM/L. When the nitrogen of the medium was exhausted, the microalga continued their growth for some time using the cell reserve of this element. The C/N ratio in cells increased from 5 to 14 and the density of the culture (relative to carbon) increased by approximately twofold. The correlation between the specific-growth rate of P. tricornutum and the C/N ratio in the cells was described by an equation similar to the Droop (1968) model. The ratio of the intracellular concentrations of carbon and chlorophyll a (C/Chl a), while reducing the specific nitrogen in the cells, increased exponentially; this effect increased with increasing light intensity. The value of the minimum cell quota for nitrogen did not depend on the light condition of culture growth.

Wastewater effects on Phaeodactylum tricornutum (Bohlin): Setting up a classification system

Phytoplankton is highly productive in marine coastal ecosystems that generally present high levels of anthropogenic pressures. Microalgae presents very high surface-to-volume ratio and may respond promptly to contaminants showing either an increase in growth or inhibition effects. Thus phytoplankton organisms provide information on the potential impacts of contaminants on the supported marine-coastal food webs. The diatom Phaeodactylum tricornutum Bohlin is commonly used in toxicity testing according to the ISO 10253:2006 standardised protocol, but a comprehensive inventory of tested substances has not been compiled yet. The aim of this study is to establish a wastewater effect score based on P. tricornutum exposed to domestic, municipal and industrial wastewaters from activated sludge sequencing batch reactor and ultra-filtration membrane biological reactors. Wastewater samples produced stimulation and inhibition effects identified by biostimulation unit (BU50) and toxicity unit (TU50) both at 50% effect, respectively. Within the stimulation scenario, toxicity was low if 0<BU50≤0.31, medium if 0.31<BU50≤1.05, high if 1.05<BU50≤1.64, and very high if BU50>1.64. Within the inhibition scenario, toxicity was low if 0<TU50≤0.07, medium if 0.07<TU50≤2.67, high if 2.67<TU50≤5.86, and very high if TU50>5.86. Results evidenced that nitrogen and phosphorus concentrations were not correlated to ecotoxicological values, probably due to the presence of undetected micronutrients, confirming the importance of toxicity-based hazard assessment.

Nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance in the diatom &amp;lt;i&amp;gt;Phaeodactylum tricornutum&amp;lt;/i&amp;gt;

Abstract. It has been proposed that ocean acidification (OA) will interact with other environmental factors to influence the overall impact of global change on biological systems. Accordingly we investigated the influence of nitrogen limitation and OA on the physiology of diatoms by growing the diatom Phaeodactylum tricornutum Bohlin under elevated (1000 μatm; high CO2 – HC) or ambient (390 μatm; low CO2 – LC) levels of CO2 with replete (110 μmol L−1; high nitrate – HN) or reduced (10 μmol L−1; low nitrate – LN) levels of NO3- and subjecting the cells to solar radiation with or without UV irradiance to determine their susceptibility to UV radiation (UVR, 280–400 nm). Our results indicate that OA and UVB induced significantly higher inhibition of both the photosynthetic rate and quantum yield under LN than under HN conditions. UVA or/and UVB increased the cells' non-photochemical quenching (NPQ) regardless of the CO2 levels. Under LN and OA conditions, activity of superoxide dismutase and catalase activities were enhanced, along with the highest sensitivity to UVB and the lowest ratio of repair to damage of PSII. HC-grown cells showed a faster recovery rate of yield under HN but not under LN conditions. We conclude therefore that nutrient limitation makes cells more prone to the deleterious effects of UV radiation and that HC conditions (ocean acidification) exacerbate this effect. The finding that nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance of the diatom P. tricornutum implies that ocean primary production and the marine biological C pump will be affected by OA under multiple stressors.

Adenosine content and growth in the diatom Phaeodactylum tricornutum (Bacillariophyceae): effect of salinity, light, temperature and nitrate

There are many known functions and regulatory mechanisms of the key metabolite adenosine in animal and plant cells, but little is known about its metabolism and how growth conditions affect the adenosine content in microalgae. In this study, we examined the influence of salinity, light intensity, temperature and nitrate concentration on growth rates and adenosine content in batch cultures of the diatom Phaeodactylum tricornutum Bohlin. A strong negative correlation was found between growth rate, as a function of both salinity and light, and adenosine content. Growth rate as a function of temperature and nitrate did not correlate with adenosine content. In silico and empirical tests revealed an apparent lack of adenosine degradation in P. tricornutum and from these analyses, we suggest that adenosine content reflects the balance between its formation from S-adenosyl-L-homocysteine (SAH) hydrolysis and AMP dephosphorylation, and its consumption by phosphorylation to AMP. The high and varying adenosine levels in the growth and stationary phases could be an important physiological adaptation to support the cellular energy charge for the cells to survive in highly fluctuating environments. Adenosine content in microalgae could also be an important parameter to describe physiological responses to different growth conditions when optimizing growth conditions to increase valuable microalgal products, such as lipids for feed in aquaculture or as biofuels.

Growth and release of extracellular organic compounds by benthic diatoms depend on interactions with bacteria

Phototrophic epilithic biofilms harbour a distinct assemblage of heterotrophic bacteria, cyanobacteria and photoautotrophic algae. Secretion of extracellular polymeric substances (EPS) by these organisms and the physicochemical properties of the EPS are important factors for the development of the biofilms. We have isolated representative diatom and bacteria strains from epilithic biofilms of Lake Constance. By pairwise co-cultivating these strains we found that diatom growth and EPS secretion by diatoms may depend on the presence of individual bacteria. Similar results were obtained after addition of spent bacterial medium to diatom cultures, suggesting that soluble substances from bacteria have an impact on diatom physiology. While searching for putative bacterial signal substances, we found that concentrations of various dissolved free amino acids (DFAA) within the diatom cultures changed drastically during co-cultivation with bacteria. Further, the secretion of extracellular carbohydrates and proteins can be influenced by bacteria or their extracellular substances. We have performed mass spectrometric peptide mapping to identify proteins which are secreted when co-cultivating the diatom Phaeodactylum tricornutum Bohlin and Escherichia coli. The identified proteins are possibly involved in signalling, extracellular carbohydrate modification and uptake, protein and amino acid modification, and cell/cell aggregation of diatom and bacteria strains. Our data indicate that diatom-bacteria biofilms might be regulated by a complex network of chemical factors involving EPS, amino acid monomers and other substances. Thus interactions with bacteria can be considered as one of the main factors driving biofilm formation by benthic diatoms.

FIRST INDUCED PLASTID GENOME MUTATIONS IN AN ALGA WITH SECONDARY PLASTIDS: psbA MUTATIONS IN THE DIATOM PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE) REVEAL CONSEQUENCES ON THE REGULATION OF PHOTOSYNTHESIS(1).

Diatoms play a crucial role in the biochemistry and ecology of most aquatic ecosystems, especially because of their high photosynthetic productivity. They often have to cope with a fluctuating light climate and a punctuated exposure to excess light, which can be harmful for photosynthesis. To gain insight into the regulation of photosynthesis in diatoms, we generated and studied mutants of the diatom Phaeodactylum tricornutum Bohlin carrying functionally altered versions of the plastidic psbA gene encoding the D1 protein of the PSII reaction center (PSII RC). All analyzed mutants feature an amino acid substitution in the vicinity of the QB -binding pocket of D1. We characterized the photosynthetic capacity of the mutants in comparison to wildtype cells, focusing on the way they regulate their photochemistry as a function of light intensity. The results show that the mutations resulted in constitutive changes of PSII electron transport rates. The extent of the impairment varies between mutants depending on the proximity of the mutation to the QB -binding pocket and/or to the nonheme iron within the PSII RC. The effects of the mutations described here for P.tricornutum are similar to effects in cyanobacteria and green microalgae, emphasizing the conservation of the D1 protein structure among photosynthetic organisms of different evolutionary origins.

Research note: High efficiency transformation of the diatom Phaeodactylum tricornutum with a promoter from the diatom Cylindrotheca fusiformis

SUMMARYA high efficiency transformation system was established for the pennate diatom Phaeodactylum tricornutum Bohlin using a plasmid containing fucoxanthin chlorophyll a/c binding protein (fcp) promoter/terminator and nitrate reductase (NR) promoter/terminator that are derived from the pennate diatom Cylindrotheca fusiformis. The plasmid that contains the zeocin resistance gene (ble) with the fcp promoter and enhanced green fluorescent protein gene (egfp) with the NR promoter was introduced into P. tricornutum using microparticle bombardment. Transformants (650 ± 58 per 108 cells) were obtained. The yield of transformants was between 1.5 and 130 times higher than previously reported P. tricornutum transformation systems. Four to seven copies of the ble gene were integrated into genomic DNA of the transformants. This high efficiency transformation system of P. tricornutum is expected to provide a powerful tool for high‐throughput analysis of gene function using homologous recombination or RNAi.

PHYTOPLANKTON COMMUNITY COMPOSITION AND GENE EXPRESSION OF FUNCTIONAL GENES INVOLVED IN CARBON AND NITROGEN ASSIMILATION(1).

A functional gene microarray was developed and used to investigate phytoplankton community composition and gene expression in the English Channel. Genes encoding the CO2 -fixation enzyme RUBISCO (rbcL) and the nitrate assimilation enzyme nitrate reductase (NR) representing several major groups of phytoplankton were included as oligonucleotide probes on the "phytoarray." Five major groups of eukaryotic phytoplankton that possess the Type 1D rbcL gene were detected, both in terms of presence (DNA) and activity (rbcL gene expression). Changes in relative signal intensity among the Type 1D rbcL probes indicated a shift from diatom dominance in the spring bloom to dominance by haptophytes and flagellates later in the summer. Because of the limitations of a smaller database, NR probes detected fewer groups, but due to the greater diversity among known NR sequences, NR probes provided higher phylogenetic resolution than did rbcL probes and identified two uncultivated diatom phylotypes as the most abundant (DNA) and active (NR gene expression) in field samples. Unidentified chlorophytes and the diatom Phaeodactylum tricornutum Bohlin were detected at both the DNA and cDNA (gene expression) levels. The reproducibility of the array was evaluated in several ways, and future directions for further improvement of probe development and sensitivity are outlined. The phytoarray provides a relatively high-resolution, high-throughput approach to assessing phytoplankton community composition in marine environments.

Phytochelatins in the Diatom Phaeodactylum tricornutum Bohlin: An Evaluation of their Use as Biomarkers of Metal Exposure in Marine Waters

The feasibility of a bioassay based on the synthesis of phytochelatins to assess metal pollution in aquatic environments was evaluated by using the marine diatom Phaeodactylum tricornutum. Short-term incubation experiments carried out in EDTA-buffered artificial seawater showed increasing cellular phytochelatin concentration with increasing free cadmium, lead or copper in the medium, indicating that phytochelatins behave as a biomarker of exposure to the bioavailable metal fraction. A linear dose-response relationship between metal exposure and phytochelatin synthesis was found in natural seawater samples enriched with known amounts of heavy metals. Phytochelatin induction tests carried out on polluted seawater samples showed an enhanced response compared to that obtained in unpolluted seawater. This finding was found to be consistent mainly with a copper contamination.

The Effect of Ni2+, Co2+, Zn2+, Cd2+ and Hg2+ on the Growth Rate of Marine Diatom Phaeodactylum tricornutum Bohlin: Microplate Growth Inhibition Test

The toxicity tests were carried out with the unicellular marine diatom Phaeodactylum tricornutum Bohlin 1897 strain CCAP 1052/1A in the f/2 medium at 20°C under continuous white light exposed to irradiance by PAR 120 μ mol m-2s-1 measured with flat sensor. The basic design of toxicity tests followed the International Standard ISO 10253 marine algal growth inhibition test (ISO 1995) and were modified according to Lukavský (1992) and Lukavský and Simmer (2001). To determine the toxicity of metals (Ni2+, Co2+, Zn2+, Cd2+ and Hg2+), on the growth rate of marine phytoplankton diatom P. tricornutum Bohlin, nickel sulphate (NiSO4 • 6H2O), cobalt chloride (CoCl2 • 6H2O), zinc sulphate (ZnSO4 • 7H2O), cadmium nitrate (Cd(NO3)2 • 4H2O), mercury chloride (HgCl2) and mercury sulfate (HgSO4) of analytical grade (99%, Kemika, Zagreb) and cobalt nitrate (Co(NO3)2 • 6H2O) of analytical grade (99%, Fluka) were used. By comparing these toxicity curves the differences in slopes could be observed. Zn, Cd, Co and Ni have a gradual “ slow” curve, while Hg has a “ sharp” one thus indicating high toxicity of Hg. The following order of toxicity was achieved: Hg>Cd>Ni>Co>Zn in the exponential phase of growth (72 h), and Hg>Ni>Co>Zn>Cd after 336 h of experiment duration (in the stationary phase of growth) with mercury as the most toxic metal. Although toxic, the effect of Hg could be attenuated under chronic conditions.P. tricornutum in the exponential phase of growth showed more tolerance to nickel than cadmium. In the stationary phase of growth a high tolerance to cadmium, zinc and cobalt was observed, while nickel showed an increase in toxicity. Besides providing screening toxicity profiles this method can be useful in determining the effects of pollutants on cell growth and viability of organisms. Also, establishing the maximum tolerance levels for organisms, this method could be used for evaluating the potential impact of pollution on aquatic system.

Genetic and phenotypic characterization of Phaeodactylum tricornutum (Bacillariophyceae) accessions1

In the last few years, genome‐based studies in diatoms have received a major boost following the genome sequencing of the centric species Thalassiosira pseudonana Hasle et Heimdal and the pleiomorphic raphid pennate diatom Phaeodactylum tricornutum Bohlin. In addition, molecular tools, such as genetic transformation, have been developed for both species. Despite these molecular advances, relatively little is known regarding the genetic diversity of the available strains of these diatoms. In this study, we have compiled a historical summary of the known P. tricornutum species resources and have provided a genetic and phenotypic overview of 10 different axenic strains. Examination of intraspecies genetic diversity based on internal transcribed spacer 2 (ITS2) sequence and amplified fragment length polymorphism (AFLP) analyses indicate four different genotypes. Seven strains are predominantly fusiform, whereas one strain is predominantly oval, and another is predominantly triradiate. Another is defined as a tropical strain because it appears better acclimated to growth at higher temperatures. Observations in the natural environment indicate that P. tricornutum is a coastal marine diatom that is able to adapt to unstable environments, such as estuaries and rock pools. Because it has rarely been noted in nature, we have developed specific primers to amplify ITS2 sequences and have successfully identified it in environmental samples. These resources should become useful tools for the diatom community when combined with the whole genome sequence and will open up a range of new possibilities for experimental investigations that can exploit the genotypic and phenotypic characteristics described.