bluuebunny/crossref_metadata_2025_split huggingface dataset:
The collapse of benthic macroalgal blooms in response to self‐shading
Authors: HIGGINS SCOTT N. , HECKY ROBERT E. , GUILDFORD STEPHANIE J. 
Published: August 2008

Summary1. Our goal was to use physiological indicators [photosynthesis–irradiance (P–I) response, nutrient status], population level feedbacks (self‐shading) and ambient environmental conditions (dissolved nutrients, light, temperature) to improve our understanding of the seasonal and spatial population dynamics ofCladophora.2. Cladophoragrew in three distinct phases, rapid growth early in the season (May–July), a mid‐season population collapse (July–August) and autumn re‐growth. Across all sites and dates, mean net maximal photosynthesis [PM(NET)] was 6.9 ± 3.9 mg O2 g DM−1 h−1, and α was 0.055 ± 0.025 mg O2 g DM−1 μmphotons−1 m−2. Mean values for critical irradiance (ICR) and the half‐saturation light intensity (IK), were 42.9 ± 32.1 and 189.3 ± 123.8 μmphotons−1 m−2 s−1respectively.3. At most sites growth was phosphorus‐limited. Values of α were significantly higher at a site influenced by a nutrient enriched river plume, where algal growth was phosphorus‐sufficient.4. Photoinhibition was not apparent in any of our P–I experiments. Even if photoinhibition had been apparent duringin vitroP–I experiments, population level photosynthetic rates in the field would be little affected because intense self‐shading restricts inhibiting irradiances to the upper few mm–cm of the algal canopy.5. Our physiological (P–I response) experiments contradicted previous assertions that high ambient temperatures, or nutrient deficiency, were primary causes of mid‐summer sloughing. In our study, sloughing occurred simultaneously at nutrient enriched and nutrient deficient sites, at temperatures well below critical values found duringin vitroexperiments, and our indicator of physiological condition (P–I response) remained unchanged leading up to, or immediately after, the sloughing event.6. Self‐shading can reduce the convexity of the P–I response withinin vitroincubations, even when the amount of algal material is low. Our experiments used 0.08 g DM of algal material that formed clumpsc.1 cm thick. Under these conditions, we estimated negligible (<1%) effects on PM, a 12% reduction in apparent values of α, and 14% and 17% increases in values of the α‐dependent termsICRandIK,respectively.7. Our results are consistent with the hypothesis that a population‐level negative feedback (self‐shading) is responsible for sloughing in dense macroalgal beds. Sloughing was probably inevitable once macroalgal bed density and thickness surpassed a critical threshold. Cells towards the base of the bed received insufficient light to maintain metabolic balance, began to decay and weaken, and became increasingly susceptible to physical detachment from shear stress.
Patterns in freshwater diatom taxonomic distinctness along an eutrophication gradient
Authors: LEIRA M. , CHEN G. , DALTON C. , IRVINE K. , TAYLOR D. 
Published: August 2008

Summary1. A variety of species richness measures have been used to assess the effects of environmental degradation on biodiversity. Such measures can be highly influenced by sample size, sampling effort, habitat type or complexity, however, and typically do not show monotonic responses to human impact. In addition to being independent of the degree of sampling effort involved in data acquisition, effective measures of biodiversity should reflect the degree of taxonomical relatedness among species within ecological assemblages and provide a basis for understanding observed diversity for a particular habitat type. Taxonomic diversity or distinctness indices emphasize the average taxonomic relatedness (i.e. degree of taxonomical closeness) between species in a community.2. Eutrophication of freshwater ecosystems, mainly due to the increased availability of nutrients, notably phosphorus, has become a major environmental problem. Two measures of taxonomic distinctness (Average Taxonomic Distinctness and Variation in Taxonomic Distinctness) were applied to surface sediment diatoms from 45 lakes across the island of Ireland to examine whether taxonomic distinctness and nutrient enrichment were significantly related at a regional scale. The lakes span a range of concentrations of epilimnic total phosphorus (TP) and were grouped into six different types, based on depth and alkalinity levels, and three different categories according to trophic state (ultra‐oligotrophic and oligotrophic; mesotrophic; and eutrophic and hyper‐eutrophic).3. The taxonomic distinctness measures revealed significant differences among lakes in the three different classes of trophic state, with nutrient‐rich lakes generally more taxonomically diverse than nutrient‐poor lakes. This implies that enrichment of oligotrophic lakes does not necessarily lead to a reduction in taxonomic diversity, at least as expressed by the indices used here. Furthermore, taxonomic distinctness was highly variable across the six different lake types regardless of nutrient level.4. Results indicate that habitat availability and physical structure within the study lakes also exert a strong influence on the pattern of taxonomic diversity. Overall the results highlight problems with the use of taxonomic diversity measures for detecting impacts of freshwater eutrophication based on diatom assemblages.
Associations between cytokine/cytokine receptor single nucleotide polymorphisms and humoral immunity to measles, mumps and rubella in a Somali population
Authors: Dhiman N. , Ovsyannikova I. G. , Vierkant R. A. , Pankratz V. S. , Jacobson R. M. , Poland G. A. 
Published: August 2008

AbstractWe genotyped a Somali population (n = 85; age ≤30 years) for 617 cytokine and cytokine receptor single nucleotide polymorphisms (SNPs) using Illumina GoldenGate genotyping to determine associations with measles, mumps and rubella immunity. Overall, 61 significant associations (P ≤ 0.01) were found between SNPs belonging to cytokine receptor genes regulating T helper (Th)1 (IL12RB2, IL2RA and B) and Th2 (IL4R and IL10RB) immunity, and cytokine (IL1B, TNFA, IL6 and IFNB1) and cytokine receptor (IL1RA, IFNAR2, IL18R1, TNFRSF1A and B) genes regulating innate immunity and variations in antibody levels to measles, mumps and/or rubella. SNPs within two major inflammatory cytokine genes, TNFA and interleukin (IL) 6, showed associations with measles‐specific antibodies. Specifically, the minor allele variant of rs1799964 (TNFA −1211 C>T) was associated with primarily seronegative values (median enzyme immunoassay index values ≤0.87; P = 0.002; q = 0.23) in response to measles disease and/or vaccination. A heterozygous variant CT for rs2069849 (IL6 +4272C>T; Phe201Phe) was also associated with seronegative values and a lower median level of antibody response to measles disease and/or vaccination (P = 0.004; q = 0.36) or measles vaccination alone (P = 0.008). Several SNPs within the coding and regulatory regions of cytokine and cytokine receptor genes showed associations with mumps and rubella antibody levels but were less informative as strong linkage disequilibrium patterns and lower frequencies for minor alleles were observed among these SNPs. Our study identifies specific SNPs in innate immune response genes that may play a role in modulating antibody responses to measles vaccination and/or infection in Somali subjects.
Suppression of SERK gene expression affects fungus tolerance and somatic embryogenesis in transgenic lettuce
Authors: Santos M. O. , Romano E. , Vieira L. S. , Baldoni A. B. , Aragão F. J. L. 
Published: August 2008

AbstractThe Somatic embryogenesis receptor‐like kinase (SERK) gene plays an important role in plant somatic and zygotic embryogenesis induction. The gene encodes an LRR‐containing receptor‐like kinase protein. Studies have been carried out focusing on different aspects of its function, but definitive conclusions on its role are far from being reached. SERK expression is generally detected in cells in which somatic or zygotic embryogenesis has been triggered. Transgenic lettuce lines were produced to silence the endogenous SERK gene using antisense RNA. The average number of seeds per flower in the R1 and R2 generations was similar for both transgenic and non‐transgenic lines. However, a reduction in the number of viable grained seeds was observed in four studied transgenic lines. Endogenous SERK expression analysis revealed the absence of detectable LsSERK gene transcripts in three transgenic lines, which presented a reduction in their ability to form in vitro somatic embryonic structures. In addition, transgenic lines showed enhanced susceptibility to the pathogenic fungus Sclerotinia sclerotiorum, when compared to control plants. The results support the idea that SERK genes might not only be involved in plant growth and development, but probably also in a general mechanism of biotic and abiotic stress perception.
Sex‐specific physiological, allocation and growth responses to water availability in the subdioecious plant Honckenya peploides
Authors: Sánchez‐Vilas J. , Retuerto R. 
Published: August 2008

AbstractThe gender of dimorphic plant species is often affected by ecophysiological variables. Differences have been interpreted as a response of the sexes to meet specific resource demands associated with reproduction. This study investigated whether sex‐specific variations in ecophysiological traits in response to water availability determine the performance of each sex in different habitats, and therefore promote extreme spatial segregation of the sexes in the subdioecious plant, Honckenya peploides. Twenty‐seven plants of each sex were individually potted in dune sand and assigned randomly to one of three water treatments. Well‐watered plants were watered daily to field capacity, whereas plants in the moderate and high‐water stress treatments received 40% and 20%, respectively, of the water given to well‐watered plants. Photochemical efficiency, leaf spectral properties and components of relative growth rate (leaf area ratio and net assimilation rate) were measured. Photochemical efficiencies integrated over time were higher in male than in female plants. Water deficit decreased maximum quantum yield in female plants more rapidly than in male plants, but female plants (unlike male plants) had recovered to initial values by the end of the experiment. Maximum quantum yield in male plants was more affected by water stress than in female plants, indicating that male plants were more susceptible to photoinhibition. The two sexes did not differ in growth rate, but male plants invested a higher proportion of their biomass in leaves, had a higher leaf area per unit biomass and lower net assimilation rate relative to female plants. Female plants had a higher water content and succulence than male plants. Differences in stomatal density between the sexes depended on water availability. The results suggest that the two sexes of H. peploides have different strategies for coping with water stress. The study also provides evidence of sex differences in allocation traits. We conclude that between‐sex differences in ecophysiological and allocation traits may contribute to explain habitat‐related between‐sex differences in performance and, therefore, the spatial segregation of the sexes.
Isolation of Resistance Gene Analogues from Flowering Dogwood (Cornus florida L.)
Authors: Shi Ainong , Kantartzi Stella K. , Mmbaga Margaret , Chen Pengyin 
Published: August 2008

AbstractCloned resistance (R) genes from a broad range of plant species are known to share similarities in DNA sequences and structural motifs. Oligonucleotide primers, designed to conserved regions of nucleotide binding site (NBS) motifs within previously cloned pathogen resistance genes, were used to amplify resistance gene analogues (RGAs) from dogwood. Twenty eight unique dogwood RGA sequences were identified and subdivided into 11 groups on the basis of nucleic acid sequence‐identity of approximately 70% or greater. Phylogenetic analysis of the predicted amino acid sequences grouped the RGAs into three distinct classes from which several subgroups were delineated based on nucleic acid sequences. Gene database searches with the consensus protein sequences of each of the three classes and respective subgroups of dogwood RGAs revealed their conserved NBS domains and homology to RGAs and known resistance genes from a variety of plant genera. Given the complete lack of knowledge regarding molecular organization of R genes in dogwood, the cloned RGAs described here may be useful as probes to map, characterize, and manipulate R genes of the dogwood genome.
Exfoliative cytology as a rapid diagnostic tool for lobomycosis
Authors: Talhari Carolina , Chrusciak‐Talhari Anette , De Souza João Vicente Braga , Araújo José Ribamar , Talhari Sinésio 
Published: August 2008

SummaryLobomycosis is a common subcutaneous mycosis in South America. It is caused by Lacazia loboi. We report two cases of lobomycosis which were diagnosed by exfoliative cytology without any special staining. We highlight this diagnostic tool as a simple, low‐cost, painless, non‐invasive and fast method for the diagnosis of lobomycosis.
Trichosporon asahii as a prospective pathogen in solid organ transplant recipients
Authors: Netsvyetayeva I. , Swoboda‐Kopeć E. , Paczek L. , Fiedor P. , Sikora M. , Jaworska‐Zaremba M. , Blachnio S. , Luczak M. 
Published: August 2008

Summary Trichosporon spp. is not an important factor of mycotic infections in immunocompetent patients. It may be a cause of invasive mycoses with a high mortality rate in patients undergoing solid organ transplantation. We have analysed the antifungal agents' susceptibility of Trichosporon asahii and its frequency of occurrence as a prospective etiological agent of infections in liver, kidney and simultaneous pancreas–kidney transplant recipients. Clinical specimens (urine, blood, peritoneal fluid and swabs) were obtained from patients hospitalised in the Institute of Transplantation Medicine, Department of General and Transplantation Surgery, Medical University of Warsaw in 2005 and 2006. Microbiological tests were performed in Mycological Laboratory, Department of Microbiology, Medical University of Warsaw. A total of 475 strains of yeast‐like fungi were isolated from clinical specimens taken from 263 liver, kidney and simultaneous pancreas–kidney transplant recipients and from 26 organ donors. Trichosporon asahii was found in 26 clinical samples taken from 18 patients and one organ donor. Positive cultures were obtained from 22 urine samples, one stoma fluid, one wound swab, one tracheal aspirate and one ejaculate. Isolates of Trichosporon asahii were found in 6% of total positive mycological cultures in the solid organ transplant recipients. Among cultured strains, 11 isolates were resistant to fluconazole, four to itraconazole and three of them demonstrated resistance to amphotericin B.
Identification and analysis of four candidate symbiosis genes from ‘Chlorochromatium aggregatum’, a highly developed bacterial symbiosis
Authors: Vogl Kajetan , Wenter Roland , Dreßen Martina , Schlickenrieder Martina , Plöscher Matthias , Eichacker Lutz , Overmann Jörg 
Published: August 2008

SummaryThe consortium ‘Chlorochromatium aggregatum’ currently represents the most highly developed interspecific association between prokaryotes. It consists of green sulfur bacteria, so‐called epibionts, which surround a central, motile, chemotrophic bacterium. Four putative symbiosis genes of the epibiont were recovered by suppression subtractive hybridization and bioinformatics approaches. These genes are transcribed constitutively and do not occur in the free‐living relatives of the epibiont. The haemagglutinin‐like putative gene products of open reading frames (ORFs) Cag0614 and Cag0616 are unusually large and contain repetitive regions and RGD tripeptides. Cag0616 harbours two βγ‐crystalline Greek key motifs. Cag1920 codes for a putative haemolysin whereas the gene product of Cag1919 is a putative RTX‐like protein. Based on detailed analyses of Cag1919, the C‐terminal amino acid sequence comprises six repetitions of the motif GGXGXD predicted to form a Ca2+‐binding beta roll. Intact ‘C. aggregatum’ consortia disaggregated upon the addition of EGTA or pyrophosphate, but stayed intact in the presence of various lectine‐binding sugars or proteolytic enzymes. Unlike other RTX toxins, a gene product of Cag1919 could not be detected by 45Ca2+ autoradiography, indicating a low abundance of the corresponding protein in the cells. The RTX‐type C‐terminus coded by Cag1919 exhibited a significant similarity to RTX modules of various proteobacterial proteins, suggesting that this putative symbiosis gene has been acquired via horizontal gene transfer from a proteobacterium.
Endosymbioses between bacteria and deep‐sea siboglinid tubeworms from an Arctic Cold Seep (Haakon Mosby Mud Volcano, Barents Sea)
Authors: Lösekann Tina , Robador Alberto , Niemann Helge , Knittel Katrin , Boetius Antje , Dubilier Nicole 
Published: August 2008

SummarySiboglinid tubeworms do not have a mouth or gut and live in obligate associations with bacterial endosymbionts. Little is currently known about the phylogeny of frenulate and moniliferan siboglinids and their symbionts. In this study, we investigated the symbioses of two co‐occurring siboglinid species from a methane emitting mud volcano in the Arctic Ocean (Haakon Mosby Mud Volcano, HMMV): Oligobrachia haakonmosbiensis (Frenulata) and Sclerolinum contortum (Monilifera). Comparative sequence analysis of the host‐specific 18S and the symbiont‐specific 16S rRNA genes of S. contortum showed that the close phylogenetic relationship of this host to vestimentiferan siboglinids was mirrored in the close relationship of its symbionts to the sulfur‐oxidizing gammaproteobacterial symbionts of vestimentiferans. A similar congruence between host and symbiont phylogeny was observed in O. haakonmosbiensis: both this host and its symbionts were most closely related to the frenulate siboglinid O. mashikoi and its gammaproteobacterial symbiont. The symbiont sequences from O. haakonmosbiensis and O. mashikoi formed a clade unaffiliated with known methane‐ or sulfur‐oxidizing bacteria. Fluorescence in situ hybridization indicated that the dominant bacterial phylotypes originated from endosymbionts residing inside the host trophosome. In both S. contortum and O. haakonmosbiensis, characteristic genes for autotrophy (cbbLM) and sulfur oxidation (aprA) were present, while genes diagnostic for methanotrophy were not detected. The molecular data suggest that both HMMV tubeworm species harbour chemoautotrophic sulfur‐oxidizing symbionts. In S. contortum, average stable carbon isotope values of fatty acids and cholesterol of −43‰ were highly negative for a sulfur oxidizing symbiosis, but can be explained by a 13C‐depleted CO2 source at HMMV. In O. haakonmosbiensis, stable carbon isotope values of fatty acids and cholesterol of −70‰ are difficult to reconcile with our current knowledge of isotope signatures for chemoautotrophic processes.
Use of benzoate as an electron acceptor by Syntrophus aciditrophicus grown in pure culture with crotonate
Authors: Mouttaki Housna , Nanny Mark A. , McInerney Michael J. 
Published: August 2008

SummaryIn methanogenic environments, the main fate of benzoate is its oxidization to acetate, H2 and CO2 by syntrophic associations of hydrogen‐producing benzoate degraders and hydrogen‐using methanogens. Here, we report the use of benzoate as an electron acceptor. Pure cultures of S. aciditrophicus simultaneously degraded crotonate and benzoate when both substrates were present. The growth rate was 0.007 h−1 with crotonate and benzoate present compared with 0.025 h−1 with crotonate alone. After 8 days of incubation, 4.12 ± 0.50 mM of cyclohexane carboxylate and 8.40 ± 0.61 mM of acetate were formed and 4.0 ± 0.04 mM of benzoate and 4.8 ± 0.5 mM of crotonate were consumed. The molar growth yield was 22.7 ± 2.1 g (dry wt) of cells per mol of crotonate compared with about 14.0 ± 0.1 g (dry wt) of cells per mol of crotonate when S. aciditrophicus was grown with crotonate alone. Cultures grown with [ring‐13C]‐benzoate and unlabelled crotonate initially formed [ring‐13C]‐labelled cyclohexane carboxylate. No 13C‐labelled acetate was detected. In addition to cyclohexane carboxylate, 13C‐labelled cyclohex‐1‐ene carboxylate was detected as an intermediate. Once almost all of the benzoate was gone, carbon isotopic analyses showed that cyclohexane carboxylate was formed from both labelled and non‐labelled metabolites. Glutarate and pimelate were also detected at this time and carbon isotopic analyses showed that each was made from a mixture labelled and non‐labelled metabolites. The increase in molar growth yield with crotonate and benzoate and the formation of [ring‐13C]‐cyclohexane carboxylate from [ring‐13C]‐benzoate in the presence of crotonate are consistent with benzoate serving as an electron acceptor.
Global distribution and diversity of coral‐associated Archaea and their possible role in the coral holobiont nitrogen cycle
Authors: Siboni Nachshon , Ben‐Dov Eitan , Sivan Alex , Kushmaro Ariel 
Published: August 2008

SummaryDiversity, distribution and genetic comparison of Archaea associated with the surface mucus of corals from three genera, namely Acanthastrea sp., Favia sp. and Fungia sp., from the Gulf of Eilat, Israel and from Heron Island, Australia were studied. Sequencing of the 16S rRNA gene of the coral‐associated Archaea revealed dominance of Crenarchaeota (79%, on average). In this phylum, 87% of the sequences were similar (≥ 97%) to the Thermoprotei, with 76% of these being similar (≥ 97%) to the ammonium oxidizer, Nitrosopumilus maritimus. Most of the coral‐associated euryarchaeotal sequences (69%) were related to marine group II, while other euryarchaeotal clades were found to be related to anaerobic methanotrophs (8%), anaerobic nitrate reducers (i.e. denitrification, 15%) and marine group III (8%). Most of the crenarchaeotal and euryarchaeotal coral‐associated 16S rRNA gene sequences from Heron Island (61%) and from the Gulf of Eilat (71%) were closely related (≥ 97%) to sequences previously derived from corals from the Virgin Islands. Analysis of archaeal amoA sequences obtained from the fungiid coral, Fungia granulosa, divided into three clades, all related to archaeal sequences previously obtained from the marine environment. These sequences were distantly related to amoA sequences previously found in association with other coral species. Preliminary experiments suggest that there is active oxidation of ammonia to nitrite in the mucus of F. granulosa. Thus, coral‐associated Archaea may contribute to nitrogen recycling in the holobiont, presumably by acting as a nutritional sink for excess ammonium trapped in the mucus layer, through nitrification and denitrification processes.
Neural correlates of variable working memory load across adult age and skill: Dissociative patterns within the fronto‐parietal network
Authors: NYBERG LARS , DAHLIN ERIKA , STIGSDOTTER NEELY ANNA , BÄCKMAN LARS 
Published: August 2008

We examined neural changes related to variations in working memory load by using an n‐back task with three levels and functional magnetic resonance imaging. Younger adults were divided into high‐ and low‐performing groups (Young‐High; Young‐Low) and compared with older adults. Relative to Young‐High, capacity‐constraints in working memory were apparent between load 1–2 for the elderly and between load 2–3 for Young‐Low. Capacity‐constraints in neural activity followed this pattern by showing a monotonically increasing response in parietal cortex and thalamus for Young‐High, whereas activity leveled off at 1‐back for the elderly and at 2‐back for Young‐Low. The response in dorsal frontal cortex followed a similar pattern with the addition that the magnitude of activation differed within capacity limitations (Old > Young at 1‐back; Young‐Low > Young‐High at 2‐back). These findings indicate that an important determinant of WM capacity is the ability to keep the frontal cortex adequately engaged in relation to current task demands.