The Macromolecular Basis of Phytoplankton C:N:P Under Nitrogen Starvation

Biogeochemical cycles in the ocean are strongly affected by the elemental stoichiometry (C:N:P) of phytoplankton, which largely reflects their macromolecular content. A greater understanding of how this macromolecular content varies among phytoplankton taxa and with resource limitation may strengthen physiological and biogeochemical modeling efforts. We determined the macromolecular basis (protein, carbohydrate, lipid, nucleic acids, pigments) of C:N:P in diatoms and prasinophytes, two globally important phytoplankton taxa, in response to N starvation. Despite their differing cell sizes and evolutionary histories, the relative decline in protein during N starvation was similar in all four species studied and largely determined variations in N content. The accumulation of carbohydrate and lipid dominated the increase in C content and C:N in all species during N starvation, but these processes differed greatly between diatoms and prasinophytes. Diatoms displayed far greater accumulation of carbohydrate with N starvation, possibly due to their greater cell size and storage capacity, resulting in larger increases in C content and C:N. In contrast, the prasinophytes had smaller increases in C and C:N that were largely driven by lipid accumulation. Variation in C:P and N:P was species-specific and mainly determined by residual P pools, which likely represent intracellular storage of inorganic P and accounted for the majority of cellular P in all species throughout N starvation. Our findings indicate that carbohydrate and lipid accumulation may play a key role in determining the environmental and taxonomic variability in phytoplankton C:N. This quantitative assessment of macromolecular and elemental content spanning several marine phytoplankton species can be used to develop physiological models for ecological and biogeochemical applications

Concurrent Exposure of Bottlenose Dolphins (Tursiops truncatus) to Multiple Algal Toxins in Sarasota Bay, Florida, USA

Sentinel species such as bottlenose dolphins (Tursiops truncatus) can be impacted by large-scale mortality events due to exposure to marine algal toxins. In the Sarasota Bay region (Gulf of Mexico, Florida, USA), the bottlenose dolphin population is frequently exposed to harmful algal blooms (HABs) of Karenia brevis and the neurotoxic brevetoxins (PbTx; BTX) produced by this dinoflagellate. Live dolphins sampled during capture-release health assessments performed in this region tested positive for two HAB toxins; brevetoxin and domoic acid (DA). Over a ten-year study period (2000–2009) we have determined that bottlenose dolphins are exposed to brevetoxin and/or DA on a nearly annual basis (i.e., DA: 2004, 2005, 2006, 2008, 2009; brevetoxin: 2000, 2004, 2005, 2008, 2009) with 36% of all animals testing positive for brevetoxin (n = 118) and 53% positive for DA (n = 83) with several individuals (14%) testing positive for both neurotoxins in at least one tissue/fluid. To date there have been no previously published reports of DA in southwestern Florida marine mammals, however the May 2008 health assessment coincided with a Pseudo-nitzschia pseudodelicatissima bloom that was the likely source of DA observed in seawater and live dolphin samples. Concurrently, both DA and brevetoxin were observed in common prey fish. Although no Pseudo-nitzschia bloom was identified the following year, DA was identified in seawater, fish, sediment, snails, and dolphins. DA concentrations in feces were positively correlated with hematologic parameters including an increase in total white blood cell (p = 0.001) and eosinophil (p<0.001) counts. Our findings demonstrate that dolphins within Sarasota Bay are commonly exposed to two algal toxins, and provide the impetus to further explore the potential long-term impacts on bottlenose dolphin health

Хирургическое лечение «раннего» рака молочной железы: что изменилось? (опыт международного сотрудничества)

The study included patients with noninvasive cancer and stage T1a-b-cN0M0 invasive breast cancer who were treated between 1985 to 2009 in Russia (at the N.N. Blokhin Russian Cancer Research Center and at the Clinic of the Russian Medical Academy of Postgraduate Training, 1036 patients), and in the Netherlands (LUMC, 560 patients, National Cancer Register, 22196 patients). The comparative analysis of surgery types between countries was carried out. The frequency of organ-preserving surgeries for early breast cancer in Russian and in the Netherlands was identical (53.7 % and 52.5 %). The percentage of organ-preserving surgeries over the past 20 years in Russia was not significantly changed, whereas the decrease in the rate of organ-preserving treatment from 56.2 % to 41.2 % was observed in the Netherlands.This is most likely due to an increase in the number of patients in postmenopause (&gt;60 years) from 53.1 % to 63.8 %. The main type of organ-preserving treatment in Russia is radical resection of the breast. In the Netherlands, lumpectomy with sentinel lymph node biopsy or axillary lymphodissection is the most common form of breast-conserving surgery today.В исследование включены пациентки с неинвазивным раком и раком молочной железы c T1a-b-cN0M0 стадией, получившие лечение с 1985 по 2009 г. в России (РОНЦ им. Н.Н. Блохина РАМН и Клиника РМАПО – 1036 больных) и в Нидерландах (LUMC – 560 пациенток, Национальный Канцрегистр – 22196 больных). Проведен сравнительный анализ типов выполненных операций по странам, а также во временных подгруппах. Частота органосохраняющего лечения при «раннем» раке молочной железы вРоссии и Нидерландах идентична – 53,7 % и 52,5 %. Доля органосохраняющих операций в течение 20 лет в России существенно не изменилась, тогда как в Нидерландах отмечено уменьшение доли органосохраняющего лечения с 56,2 % до 41,2 %, что, вероятнее всего, объясняется увеличением числа пациенток, находящихся в постменопаузе (&gt;60 лет) с 53,1 % до 63,8 %. Основным вариантом органосохраняющего лечения в России является радикальная резекция молочной железы, в Нидерландах – лампэктомия с БСЛУ или аксиллярной лимфодиссекцией, причем БСЛУ и в настоящее время не является «рутинной» операцией во всей стране

Correction: Nitrogen starvation induces distinct photosynthetic responses and recovery dynamics in diatoms and prasinophytes.

[This corrects the article DOI: 10.1371/journal.pone.0195705.]

Phylogenetic Diversity in the Macromolecular Composition of Microalgae.

The elemental stoichiometry of microalgae reflects their underlying macromolecular composition and influences competitive interactions among species and their role in the food web and biogeochemistry. Here we provide a new estimate of the macromolecular composition of microalgae using a hierarchical Bayesian analysis of data compiled from the literature. The median macromolecular composition of nutrient-sufficient exponentially growing microalgae is 32.2% protein, 17.3% lipid, 15.0% carbohydrate, 17.3% ash, 5.7% RNA, 1.1% chlorophyll-a and 1.0% DNA as percent dry weight. Our analysis identifies significant phylogenetic differences in macromolecular composition undetected by previous studies due to small sample sizes and the large inherent variability in macromolecular pools. The phylogenetic differences in macromolecular composition lead to variations in carbon-to-nitrogen ratios that are consistent with independent observations. These phylogenetic differences in macromolecular and elemental composition reflect adaptations in cellular architecture and biochemistry; specifically in the cell wall, the light harvesting apparatus, and storage pools

Mutations in the 1A domain of keratin 9 in patients with epidermolytic palmoplantar keratoderma

Epidermolytic palmoplantar keratoderma is an autosomal dominant skin disorder characterized by hyperkeratosis of the palms and soles. Ultrastructurally the disease exhibits abnormal keratin filament networks and tonofilament clumping like that found in the keratin disorders of epidermolysis bullosa simplex and epidermolytic hyperkeratosis. The disease has been mapped to chromosome 17q11-q23 in the region of the type 1 keratin gene locus and more recently mutations have been found in the palmoplantar specific keratin, keratin 9. We have analyzed six unrelated incidences of epidermolytic palmoplantar keratoderma for mutations in their keratin 9 genes. In two of these, we have identified mutations that alter critical residues within the highly conserved helix initiation motif at the beginning of the rod domain of keratin 9. In a three-generation Middle Eastern kindred we found a C to T transition at codon 162 that results in an arginine to tryptophan substitution at position 10 of the 1A alpha-helical domain, thus confirming this codon as a hot spot for mutation in keratin 9. The other mutation found involves a T to C transition at codon 167 that results in the expression of a serine residue in place of the normal leucine at position 15 of the 1A segment and is the first documentation of this mutation in this gene. The identification of these substitutions extends the current catalog of disease causing mutations in keratin 9

Nitrogen starvation induces distinct photosynthetic responses and recovery dynamics in diatoms and prasinophytes

<div><p>Nitrogen stress is an important control on the growth of phytoplankton and varying responses to this common condition among taxa may affect their relative success within phytoplankton communities. We analyzed photosynthetic responses to nitrogen (N) stress in two classes of phytoplankton that often dominate their respective size ranges, diatoms and prasinophytes, selecting species of distinct niches within each class. Changes in photosynthetic structures appeared similar within each class during N stress, but photophysiological and growth responses were more species- or niche-specific. In the coastal diatom <i>Thalassiosira pseudonana</i> and the oceanic diatom <i>T</i>. <i>weissflogii</i>, N starvation induced large declines in photosynthetic pigments and Photosystem II (PSII) quantity and activity as well as increases in the effective absorption cross-section of PSII photochemistry (<i>σʹ</i>_PSII). These diatoms also increased photoprotection through energy-dependent non-photochemical quenching (NPQ) during N starvation. Resupply of N in diatoms caused rapid recovery of growth and relaxation of NPQ, while recovery of PSII photochemistry was slower. In contrast, the prasinophytes <i>Micromonas</i> sp., an Arctic Ocean species, and <i>Ostreococcus tauri</i>, a temperate coastal eutrophile, showed little change in photosynthetic pigments and structures and a decline or no change, respectively, in <i>σʹ</i>_PSII with N starvation. Growth and PSII function recovered quickly in <i>Micromonas</i> sp. after resupply of N while <i>O</i>. <i>tauri</i> failed to recover N-replete levels of electron transfer from PSII and growth, possibly due to their distinct photoprotective strategies. <i>O</i>. <i>tauri</i> induced energy-dependent NPQ for photoprotection that may suit its variable and nutrient-rich habitat. <i>Micromonas</i> sp. relies upon both energy-dependent NPQ and a sustained, energy-independent NPQ mechanism. A strategy in <i>Micromonas</i> sp. that permits photoprotection with little change in photosynthetic structures is consistent with its Arctic niche, where low temperatures and thus low biosynthetic rates create higher opportunity costs to rebuild photosynthetic structures.</p></div

Phylogenetic Diversity in the Macromolecular Composition of Microalgae

<div><p>The elemental stoichiometry of microalgae reflects their underlying macromolecular composition and influences competitive interactions among species and their role in the food web and biogeochemistry. Here we provide a new estimate of the macromolecular composition of microalgae using a hierarchical Bayesian analysis of data compiled from the literature. The median macromolecular composition of nutrient-sufficient exponentially growing microalgae is 32.2% protein, 17.3% lipid, 15.0% carbohydrate, 17.3% ash, 5.7% RNA, 1.1% chlorophyll-a and 1.0% DNA as percent dry weight. Our analysis identifies significant phylogenetic differences in macromolecular composition undetected by previous studies due to small sample sizes and the large inherent variability in macromolecular pools. The phylogenetic differences in macromolecular composition lead to variations in carbon-to-nitrogen ratios that are consistent with independent observations. These phylogenetic differences in macromolecular and elemental composition reflect adaptations in cellular architecture and biochemistry; specifically in the cell wall, the light harvesting apparatus, and storage pools.</p></div

Nitrogen starvation induces distinct photosynthetic responses and recovery dynamics in diatoms and prasinophytes - Fig 1

<p>Growth rate (<i>μ</i>) from N-replete balanced growth to N starvation and in N-starved sub-cultures following the addition of nitrate in (A) <i>T</i>. <i>pseudonana</i>, (B) <i>T</i>. <i>weissflogii</i>, (C) <i>O</i>. <i>tauri</i>, and (D) <i>Micromonas</i> sp. (X) symbols indicate sampling points for cell composition and photochemistry. Recovery after the resupply of N is shown for subcultures collected at early (ES, white triangles), mid (MS, gray triangles), and late stationary (LS, black triangles) phases. The dashed line indicates the <i>μ</i>_<i>max</i> for a species determined during N-replete, balanced growth. Error bars indicate one standard deviation among triplicate cultures.</p