"Candidatus Accumulibacter delftensis": A clade IC novel polyphosphate-accumulating organism without denitrifying activity on nitrate.

Populations of "Candidatus Accumulibacter", a known polyphosphate-accumulating organism, within clade IC have been proposed to perform anoxic P-uptake activity in enhanced biological phosphorus removal (EBPR) systems using nitrate as electron acceptor. However, no consensus has been reached on the ability of "Ca. Accumulibacter" members of clade IC to reduce nitrate to nitrite. Discrepancies might relate to the diverse operational conditions which could trigger the expression of the Nap and/or Nar enzyme and/or to the accuracy in clade classification. This study aimed to assess whether and how certain operational conditions could lead to the enrichment and enhance the denitrification capacity of "Ca. Accumulibacter" within clade IC. To study the potential induction of the denitrifying enzyme, an EBPR culture was enriched under anaerobic-anoxic-oxic (A2O) conditions that, based on fluorescence in situ hybridization and ppk gene sequencing, was composed of around 97% (on a biovolume basis) of affiliates of "Ca. Accumulibacter" clade IC. The influence of the medium composition, sludge retention time (SRT), polyphosphate content of the biomass (poly-P), nitrate dosing approach, and minimal aerobic SRT on potential nitrate reduction were studied. Despite the different studied conditions applied, only a negligible anoxic P-uptake rate was observed, equivalent to maximum 13% of the aerobic P-uptake rate. An increase in the anoxic SRT at the expenses of the aerobic SRT resulted in deterioration of P-removal with limited aerobic P-uptake and insufficient acetate uptake in the anaerobic phase. A near-complete genome (completeness = 100%, contamination = 0.187%) was extracted from the metagenome of the EBPR biomass for the here-proposed "Ca. Accumulibacter delftensis" clade IC. According to full-genome-based phylogenetic analysis, this lineage was distant from the canonical "Ca. Accumulibacter phosphatis", with closest neighbor "Ca. Accumulibacter sp. UW-LDO-IC" within clade IC. This was cross-validated with taxonomic classification of the ppk1 gene sequences. The genome-centric metagenomic analysis highlighted the presence of genes for assimilatory nitrate reductase (nas) and periplasmic nitrate reductase (nap) but no gene for respiratory nitrate reductases (nar). This suggests that "Ca. Accumulibacter delftensis" clade IC was not capable to generate the required energy (ATP) from nitrate under strict anaerobic-anoxic conditions to support an anoxic EBPR metabolism. Definitely, this study stresses the incongruence in denitrification abilities of "Ca. Accumulibacter" clades and reflects the true intra-clade diversity, which requires a thorough investigation within this lineage.

The Microbial Database for Danish wastewater treatment plants with nutrient removal (MiDas-DK) - a tool for understanding activated sludge population dynamics and community stability.

Since 2006 more than 50 Danish full-scale wastewater treatment plants with nutrient removal have been investigated in a project called 'The Microbial Database for Danish Activated Sludge Wastewater Treatment Plants with Nutrient Removal (MiDas-DK)'. Comprehensive sets of samples have been collected, analyzed and associated with extensive operational data from the plants. The community composition was analyzed by quantitative fluorescence in situ hybridization (FISH) supported by 16S rRNA amplicon sequencing and deep metagenomics. MiDas-DK has been a powerful tool to study the complex activated sludge ecosystems, and, besides many scientific articles on fundamental issues on mixed communities encompassing nitrifiers, denitrifiers, bacteria involved in P-removal, hydrolysis, fermentation, and foaming, the project has provided results that can be used to optimize the operation of full-scale plants and carry out trouble-shooting. A core microbial community has been defined comprising the majority of microorganisms present in the plants. Time series have been established, providing an overview of temporal variations in the different plants. Interestingly, although most microorganisms were present in all plants, there seemed to be plant-specific factors that controlled the population composition thereby keeping it unique in each plant over time. Statistical analyses of FISH and operational data revealed some correlations, but less than expected. MiDas-DK (www.midasdk.dk) will continue over the next years and we hope the approach can inspire others to make similar projects in other parts of the world to get a more comprehensive understanding of microbial communities in wastewater engineering.

Digging into the extracellular matrix of a complex microbial community using a combined metagenomic and metaproteomic approach.

Knowledge about identity and function of extracellular polymeric substances (EPS) in complex microbial communities is sparse, although these components have a large influence on the function of the microbial communities. We investigated the presence of selected genes potentially involved in EPS production in a 145 Mbp metagenome prepared by Illumina sequencing from a full-scale wastewater treatment plant carrying out enhanced biological phosphorus removal (EBPR). A range of genes involved in alginate production was identified and assigned mainly to bacteria from the phylum Bacteroidetes. Furthermore, several proteins in the EPS matrix were extracted, purified and identified by mass spectrometry. By using the metagenome as a reference for the metaproteomic analysis, more proteins were identified compared to using only publicly available databases. This illustrates the low degree of similarity between the bacteria in the EBPR community and the sequenced bacteria in the public databases. Hence, the combination of metagenomics and metaproteomics presented here is needed to investigate the identity of the proteins in the EPS matrix.

Birefringence-induced splitting of the zero-dispersion wavelength in nonlinear photonic crystal fibers.

We investigate how the strongly wavelength-dependent birefringence in nonlinear photonic crystal fibers leads to a splitting in the zero-dispersion wavelength for the two polarizations. We translate the requirements for the maximum splitting of the zero-dispersion wavelength to requirements for transverse structural uniformity by adopting a simple effective-index approach in which the birefringence is calculated in a step-index fiber with an elliptical core. We find that to reduce the splitting to less than 1 nm the birefringence should be less than 2 x 10(-5), resulting in a transverse uniformity requirement of 1-3%, depending on the index step from the core to the cladding.

Predicting macrobending loss for large-mode area photonic crystal fibers.

We report on an easy-to-evaluate expression for the prediction of the bend-loss for a large mode area photonic crystal fiber (PCF) with a triangular air-hole lattice. The expression is based on a recently proposed formulation of the V-parameter for a PCF and contains no free parameters. The validity of the expression is verified experimentally for varying fiber parameters as well as bend radius. The typical deviation between the position of the measured and the predicted bend loss edge is within measurement uncertainty.

Two male-sterile mutants of Zea Mays (Poaceae) with an extra cell division in the anther wall.

Two recessive male-sterile mutants of maize with similar patterns of pollen abortion were studied. Genetic studies showed that one of the two mutations was allelic with a previously identified male-sterility locus (ms23) and the other mutation was in a newly identified male-sterility locus (ms32). Cytological characterization of homozygous mutants and fertile heterozygous control siblings was performed using brightfield, fluorescence, and electron microscopy. During normal anther development, the final anther wall periclinal division divides the secondary parietal anther wall layer into the middle layer and tapetum, forming an anther with four wall layers. This is followed by differentiation of the tapetal cells into protoplastic binucleate, secretory tissue. In both the ms23 and ms32 mutants, the prospective tapetal layer divided into two layers, termed t1 and t2, forming an anther with five wall layers. Neither the t1 nor the t2 layers differentiated normally into tapetal layers, as determined by examination of cell walls, nucleus number, and cytoplasmic organization. Pollen mother cells aborted after the onset of prophase I of meiosis, suggesting that an early developmental coordination may exist between tapetum and pollen mother cells.

Flavanone 3-hydroxylase transcripts and flavonol accumulation are temporally coordinate in maize anthers.

Flavanone 3-hydroxylase (F3H) activity is necessary for the production of both flavonols and anthocyanins. Flavonols are required for functional pollen in maize whereas anthocyanins are non-essential pigments. A cDNA for F3H was isolated from Zea mays using a heterologous sequence from Antirrhinum majus. Comparison of the deduced amino acid sequence of maize F3H with other F3H sequences confirmed that the protein is highly conserved among widely divergent plant species. The F3H gene is present in a single copy located at the tip of chromosome 2S. High levels of F3H gene expression were detected in pigmented husk and 26-day postpollination kernels; lower levels in 18-day postpollination kernels and in coleoptiles of germinating seedlings. Slot blot analysis showed that F3H transcript levels in young seedlings are increased by high fluence-rate white light treatment in the presence of the anthocyanin regulatory gene -r. HPLC analysis of extracts from developmentally staged anthers showed that flavonol accumulation begins at the uninucleate microspore stage, continues until maturity, and is not controlled by -r. When the expression pattern of several flavonoid biosynthetic genes was analyzed during microsporogenesis, only F3H transcript accumulation was coordinate with the appearance of flavonols in anthers.

Assessment at CT of the rheumatoid shoulder with surgical correlation.

Eleven shoulders in 10 patients with rheumatoid arthritis were examined by conventional radiography and CT prior to cup hemiarthroplasty of the humeral head and the results were compared with the surgical findings. There was good agreement between preoperative CT and surgical findings. Humeral head cavities and erosions, with cortical boundaries, could be seen more accurately at CT than at conventional radiography. The HU of their contents corresponded to those of soft tissue, being granulomatous in nature at surgery. In 8 humeral heads CT disclosed large areas of fatty degeneration of bone marrow with HU between -10 HU and -76 HU that were not visible on the conventional radiographs. These "fatty cysts" had no cortical boundaries, unlike inflammatory granulomas, but both lesions may influence the surgical approach to hemiarthroplasty.

Effect of radiographic contrast media on granulocyte phagocytosis of Escherichia coli in a whole blood flow cytometric assay.

RATIONALE AND OBJECTIVES: Earlier studies have demonstrated an adverse effect of radiographic contrast media (CM) on granulocyte phagocytosis. Most studies in the past have depended on granulocyte separative procedures that may themselves affect granulocyte functions. This study was performed to evaluate the effect of CM on phagocytosis using a flow cytometric assay allowing more physiological assay conditions. METHODS: Twenty consecutive patients were blindly randomized to receive the nonionic ratio 3.0 CM iohexol or the ionic ratio 3.0 CM ioxaglate for intravenous urography. Granulocyte phagocytic potential was measured before and at 1, 5, and 20 minutes after CM administration with a flow cytometric whole blood method evaluating the ingestion of complement- and immunoglobulin G (IgG)-opsonized fluorescent Escherichia Coli bacteria. RESULTS: The ability of granulocytes to phagocytize opsonized E. Coli was adversely affected by both CM used. Compared with baseline values, significantly decreased phagocytic activity was observed for iohexol at 1, 5, and 20 minutes and for ioxaglate at 1 and 5 minutes. The largest decrease with ioxaglate was from 85.3 +/- 10.5 to 69.3 +/- 16.3 (5 minutes), and the largest change with iohexol was from 87.1 +/- 8.5 to 74.5 +/- 15.9 (5 minutes). CONCLUSION: These results confirm earlier reports that ionic and nonionic CM adversely affect the phagocytic ability of granulocytes after intravenous administration.

Quantitative trait loci for plant height in four maize populations and their associations with qualitative genetic loci.

We report that plant height quantitative trait loci (QTLs) identified in a given small population are not consistent with QTLs identified in other small populations, and that most QTLs are in close proximity to mapped qualitative genetic loci. These observations provide evidence to support the hypothesis that qualitative genetic loci are the same loci that affect quantitative traits, and affirm that these modest experiments probably identify real QTLs.

Study of two different recombination events in maize cmsT-regenerated plants during reversion to fertility.

The change of phenotype from sterility to fertility for some cmsT callus tissue culture regenerated plants and their progenies has been correlated with changes in their mitochondrial genome. Those changes that have been analyzed here are the result of recombination events. Two different sets of repeated sequences have been found to be involved in those recombination events. The most common one is a recombination through a 127-bp repeat between various independently isolated revertants. The second one is a recombination through a 58-bp repeat. In every case the products of recombination containing the urf13 gene have been deleted.