Cellular Source and Mechanisms of High Transcriptome Complexity in the Mammalian Testis

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The easy road to genome‐wide medium density SNP screening in a non‐model species: development and application of a 10 K SNP‐chip for the house sparrow (Passer domesticus)

With the advent of next generation sequencing, new avenues have opened to study genomics in wild populations of non‐model species. Here, we describe a successful approach to a genome‐wide medium density Single Nucleotide Polymorphism (SNP) panel in a non‐model species, the house sparrow (Passer domesticus), through the development of a 10 K Illumina iSelect HD BeadChip. Genomic DNA and cDNA derived from six individuals were sequenced on a 454 GS FLX system and generated a total of 1.2 million sequences, in which SNPs were detected. As no reference genome exists for the house sparrow, we used the zebra finch (Taeniopygia guttata) reference genome to determine the most likely position of each SNP. The 10 000 SNPs on the SNP‐chip were selected to be distributed evenly across 31 chromosomes, giving on average one SNP per 100 000 bp. The SNP‐chip was screened across 1968 individual house sparrows from four island populations. Of the original 10 000 SNPs, 7413 were found to be variable, and 99% of these SNPs were successfully called in at least 93% of all individuals. We used the SNP‐chip to demonstrate the ability of such genome‐wide marker data to detect population sub‐division, and compared these results to similar analyses using microsatellites. The SNP‐chip will be used to map Quantitative Trait Loci (QTL) for fitness‐related phenotypic traits in natural populations.     

Associations between dru Types and SCCmec Cassettes

Molecular typing is an important tool in the investigation of methicillin resistant Staphylococcus aureus (MRSA) outbreaks and in following the evolution of MRSA. The staphylococcal cassette chromosome mec (SCCmec) contains a hypervariable region with a variable number of 40 bp repeats named direct repeat units (dru). The dru region has been suggested as a supplementary typing method for MRSA and an international nomenclature exists. The purpose of this study was to investigate the diversity and variability of the dru region in a diverse collection of MRSA. We studied 302 MRSA isolates harbouring SCCmec types I to VI. The isolates represented a broad genetic background based on Staphylococcal protein A (spa) typing and multilocus sequence typing (MLST) and included 68 isolates (68 patients) from an outbreak with t024-ST8-IVa and 26 isolates from the same patient. Sequencing identified 53 dru types (dt) in 283 isolates, while eighteen isolates contained no dru repeats and one isolate resisted sequencing. The most common dru type, dt10a, was present in 53% of the sequenced isolates and was found in all SCCmec types, except type II. Seven (10%) of the 68 epidemiologically related patients had isolates with dru type variants indicating that dru typing is not useful as a first line epidemiological typing tool. However, MRSA isolates cultured from a single patient over a three year period exhibited a single dru type. The finding of dt10a in most SCCmec types suggests that dru and mecA originate from the same Staphylococcus species.     

Does Coral Disease Affect Symbiodinium? Investigating the Impacts of Growth Anomaly on Symbiont Photophysiology

Growth anomaly (GA) is a commonly observed coral disease that impairs biological functions of the affected tissue. GA is prevalent at Wai ‘ōpae tide pools, southeast Hawai ‘i Island. Here two distinct forms of this disease, Type A and Type B, affect the coral, Montipora capitata . While the effects of GA on biology and ecology of the coral host are beginning to be understood, the impact of this disease on the photophysiology of the dinoflagellate symbiont, Symbiodinium spp., has not been investigated. The GA clearly alters coral tissue structure and skeletal morphology and density. These tissue and skeletal changes are likely to modify not only the light micro-environment of the coral tissue, which has a direct impact on the photosynthetic potential of Symbiodinium spp., but also the physiological interactions within the symbiosis. This study utilized Pulse amplitude modulation fluorometry (PAM) to characterize the photophysiology of healthy and GA-affected M . capitata tissue. Overall, endosymbionts within GA-affected tissue exhibit reduced photochemical efficiency. Values of both F_v/F_m and ΔF/ F_m’ were significantly lower (p<0.01) in GA tissue compared to healthy and unaffected tissues. Tracking the photophysiology of symbionts over a diurnal time period enabled a comparison of symbiont responses to photosynthetically available radiation (PAR) among tissue conditions. Symbionts within GA tissue exhibited the lowest values of ΔF/F_m’ as well as the highest pressure over photosystem II (p<0.01). This study provides evidence that the symbionts within GA-affected tissue are photochemically compromised compared to those residing in healthy tissue.     

Phylogeny and physiology of candidate phylum ‘Atribacteria' (OP9/JS1) inferred from cultivation-independent genomics

The ‘Atribacteria'' is a candidate phylum in the Bacteria recently proposed to include members of the OP9 and JS1 lineages. OP9 and JS1 are globally distributed, and in some cases abundant, in anaerobic marine sediments, geothermal environments, anaerobic digesters and reactors and petroleum reservoirs. However, the monophyly of OP9 and JS1 has been questioned and their physiology and ecology remain largely enigmatic due to a lack of cultivated representatives. Here cultivation-independent genomic approaches were used to provide a first comprehensive view of the phylogeny, conserved genomic features and metabolic potential of members of this ubiquitous candidate phylum. Previously available and heretofore unpublished OP9 and JS1 single-cell genomic data sets were used as recruitment platforms for the reconstruction of atribacterial metagenome bins from a terephthalate-degrading reactor biofilm and from the monimolimnion of meromictic Sakinaw Lake. The single-cell genomes and metagenome bins together comprise six species- to genus-level groups that represent most major lineages within OP9 and JS1. Phylogenomic analyses of these combined data sets confirmed the monophyly of the ‘Atribacteria'' inclusive of OP9 and JS1. Additional conserved features within the ‘Atribacteria'' were identified, including a gene cluster encoding putative bacterial microcompartments that may be involved in aldehyde and sugar metabolism, energy conservation and carbon storage. Comparative analysis of the metabolic potential inferred from these data sets revealed that members of the ‘Atribacteria'' are likely to be heterotrophic anaerobes that lack respiratory capacity, with some lineages predicted to specialize in either primary fermentation of carbohydrates or secondary fermentation of organic acids, such as propionate.     

Origin of the S‐Shaped JV Curve and the Light‐Soaking Issue in Inverted Organic Solar Cells

Inverted organic solar cells generally exhibit a strong s‐shaped kink in the current–voltage characteristics (JV curve) that may be removed by exposure to UV light (light‐soaking) leading to a drastically improved performance. Using in‐device characterization methods the origin of the light‐soaking issue in inverted solar cells employing titanium dioxide (TiO₂) as an electron selective layer is clarified. An injected hole reservoir accumulated at the TiO₂/organic interface of the pristine device is observed from extraction current transients; the hole reservoir increases the recombination and results in an s‐shape in the JV curve of pristine devices. The hole reservoir and the s‐shape is a result of the energetics at the selective contact in the pristine device; the effect of UV exposure is to decrease the work function of the indium tin oxide/TiO₂‐contact, increasing the built‐in potential. This hinders the build‐up of the hole reservoir and the s‐shape is removed. The proposed model is in excellent agreement with drift‐diffusion simulations.     

Phthalates Are Metabolised by Primary Thyroid Cell Cultures but Have Limited Influence on Selected Thyroid Cell Functions In Vitro

Phthalates are plasticisers added to a wide variety of products, resulting in measurable exposure of humans. They are suspected to disrupt the thyroid axis as epidemiological studies suggest an influence on the peripheral thyroid hormone concentration. The mechanism is still unknown as only few in vitro studies within this area exist. The aim of the present study was to investigate the influence of three phthalate diesters (di-ethyl phthalate, di-n-butyl phthalate (DnBP), di-(2-ethylhexyl) phthalate (DEHP)) and two monoesters (mono-n-butyl phthalate and mono-(2-ethylhexyl) phthalate (MEHP)) on the differentiated function of primary human thyroid cell cultures. Also, the kinetics of phthalate metabolism were investigated. DEHP and its monoester, MEHP, both had an inhibitory influence on 3''-5''-cyclic adenosine monophosphate secretion from the cells, and MEHP also on thyroglobulin (Tg) secretion from the cells. Results of the lactate dehydrogenase-measurements indicated that the MEHP-mediated influence was caused by cell death. No influence on gene expression of thyroid specific genes (Tg, thyroid peroxidase, sodium iodine symporter and thyroid stimulating hormone receptor) by any of the investigated diesters could be demonstrated. All phthalate diesters were metabolised to the respective monoester, however with a fall in efficiency for high concentrations of the larger diesters DnBP and DEHP. In conclusion, human thyroid cells were able to metabolise phthalates but this phthalate-exposure did not appear to substantially influence selected functions of these cells.