Phosphorus fractions and alkaline phosphatase activity in sediments of a large eutrophic Chinese lake (Lake Taihu)

Spatial, vertical, and seasonal variations in phosphorus fractions and in alkaline phosphatase activity (APA) were investigated in sediments in a large-shallow eutrophic Chinese lake (Lake Taihu) in 2003-2004. The phosphorus content was highest in the most seriously polluted lake area. Iron-bound phosphorus (Fe(OOH)-P) dominated (47% on average) among the phosphorus fractions determined according to Golterman (Hydrobiologia 335:87-95, 1996). Notably, organically-bound P comprised a further significant additional portion (acid-soluble + hot NaOH-extractable organic P = 25%), which was highest at the most polluted sites. The Fe(OOH)-P content was the lowest in spring (April, 2004), suggesting that degradation of organic matter led to the release of iron-bound phosphates. Sediment APA showed a significant positive relationship with both organically-bound P and Fe(OOH)-P. Consequently, organically-bound P is an important portion of the sediment phosphorus in Lake Taihu. It is mainly derived from freshly-settled autochthonous particles and from external discharges. Organically-bound P induces APA and may lead to the release of bioavailable phosphates from the organic sediments, thereby accelerating lake eutrophication.Spatial, vertical, and seasonal variations in phosphorus fractions and in alkaline phosphatase activity (APA) were investigated in sediments in a large-shallow eutrophic Chinese lake (Lake Taihu) in 2003-2004. The phosphorus content was highest in the most seriously polluted lake area. Iron-bound phosphorus (Fe(OOH)-P) dominated (47% on average) among the phosphorus fractions determined according to Golterman (Hydrobiologia 335:87-95, 1996). Notably, organically-bound P comprised a further significant additional portion (acid-soluble + hot NaOH-extractable organic P = 25%), which was highest at the most polluted sites. The Fe(OOH)-P content was the lowest in spring (April, 2004), suggesting that degradation of organic matter led to the release of iron-bound phosphates. Sediment APA showed a significant positive relationship with both organically-bound P and Fe(OOH)-P. Consequently, organically-bound P is an important portion of the sediment phosphorus in Lake Taihu. It is mainly derived from freshly-settled autochthonous particles and from external discharges. Organically-bound P induces APA and may lead to the release of bioavailable phosphates from the organic sediments, thereby accelerating lake eutrophication

Measuring oxygen surface exchange kinetics on mixed-conducting composites by electrical conductivity relaxation

The oxygen release kinetics of mixed-conducting Sr2Fe1.5Mo0.5O6 d–Sm0.2Ce0.8O2 d (SFM–SDC) dualphase composites has been investigated, at 750 C, as a function of the SDC phase volume fraction using electrical conductivity relaxation (ECR) under reducing atmospheres, extending our previous work on the oxygen incorporation kinetics of these composites under oxidizing conditions. Gas mixtures of H2/H2O and CO/CO2 were used to control step changes in the oxygen partial pressure (pO2) in the range 10 24 to 10 20 atm. At the conditions of the experiments, oxygen re-equilibration is entirely controlled by the surface exchange kinetics. A model is developed which allows deconvolution of the effective time constant of the relaxation process in terms of the intrinsic contributions of the components to oxygen surface exchange and synergetic contributions caused by heterogeneous interfaces. The oxygen surface exchange kinetics under H2/H2O atmosphere is found to be a weighted average of the intrinsic contributions of SFM and SDC phases. No evidence is found for an enhanced exchange rate at the SFM–SDC–gas triple phase boundaries (TPB). Synergetic contributions arise under CO/CO2 atmosphere, enhancing the rate of oxygen surface exchange up to a factor of 2.4. The obtained results are discussed in terms of the surface microstructure of the composites from image analysis. Overall, the results of this and our previous study confirm that the triple phase boundaries in SFM–SDC composites significantly accelerate the oxygen incorporation kinetics under oxidizing conditions, but only modestly, or even negligibly, influence the oxygen release kinetics under reducing conditions

Electrical conductivity relaxation of Sr2Fe1.5Mo0.5O6−δ–Sm0.2Ce0.8O1.9 dual-phase composites

The oxygen incorporation kinetics of Sr2Fe1.5Mo0.5O6 d–Sm0.2Ce0.8O1.9 (SFM–SDC) dual-phase composites has been investigated, at 750 C, as a function of SDC phase volume fraction using electrical conductivity relaxation. It is shown that the oxygen re-equilibration kinetics in the range of oxygen partial pressure (pO2) from 0.01 to 1 atm is limited by the surface exchange rate. The effective surface exchange coefficient of the composites is found to increase profoundly upon increasing the phase volume fraction of the oxide electrolyte phase SDC. The results are interpreted to reflect the synergistic oxygen incorporation at the SFM–SDC–gas triple phase boundaries (TPBs), which occurs in addition to the direct incorporation via the surface of the perovskite mixed conductor SFM. Already at a SDC phase volume fraction of 0.105, the uptake of oxygen via the synergistic TPB route (referred to as route III), following a step change in the surrounding pO2, comprises more than 75% of the overall uptake of oxygen by the composite. It is further concluded that under the conditions of the experiments the twophase SFM–SDC boundaries allow for a facile exchange of oxygen ions between both involved phases

Rapid and Simple Detection of Trichosporon asahii by Optimized Colony PCR

Trichosporon asahii is the major pathogen causing invasive trichosporonosis. Conventional methods of its detection are time-consuming or costly and often require complex DNA extraction and purification steps, which hinders rapid clinical diagnosis. In this study, we evaluated colony PCR, which directly uses colonies or trace clinical samples as the template for amplification, for rapid detection of T. asahii infection. Four methods, namely, direct colony, freeze-thaw, glass beads, and enzymolysis, were compared to select the best DNA extraction strategy. We subsequently designed and screened species-specific primers targeting the intergenic spacer 1 (IGS1) of the ribosomal DNA of T. asahii and used them to detect mock infection clinical samples. The species-specific colony PCR based on glass beads proved advantageous, with short procedure time (154.8 ± 0.6 min), good sensitivity (detection limit, 102 CFU/mL), and specificity for T. asahii, indicating that this method can be used for the rapid and simple identification of clinical samples of T. asahii infection

Chromosome Genome Assembly of Cromileptes altivelis Reveals Loss of Genome Fragment in Cromileptes Compared with Epinephelus Species

The humpback grouper (Cromileptes altivelis), an Epinephelidae species, is patchily distributed in the reef habitats of Western Pacific water. This grouper possesses a remarkably different body shape and notably low growth rate compared with closely related grouper species. For promoting further research of the grouper, in the present study, a high-quality chromosome-level genome of humpback grouper was assembled using PacBio sequencing and high-throughput chromatin conformation capture (Hi-C) technology. The assembled genome was 1.013 Gb in size with 283 contigs, of which, a total of 143 contigs with 1.011 Gb in size were correctly anchored into 24 chromosomes. Moreover, a total of 26,037 protein-coding genes were predicted, of them, 25,243 (96.95%) genes could be functionally annotated. The high-quality chromosome-level genome assembly will provide pivotal genomic information for future research of the speciation, evolution and molecular-assisted breeding in humpback groupers. In addition, phylogenetic analysis based on shared single-copy orthologues of the grouper species showed that the humpback grouper is included in the Epinephelus genus and clustered with the giant grouper in one clade with a divergence time of 9.86 Myr. In addition, based on the results of collinearity analysis, a gap in chromosome 6 of the humpback grouper was detected; the missed genes were mainly associated with immunity, substance metabolism and the MAPK signal pathway. The loss of the parts of genes involved in these biological processes might affect the disease resistance, stress tolerance and growth traits in humpback groupers. The present research will provide new insight into the evolution and origin of the humpback grouper