Transcription, signaling receptor activity, oxidative phosphorylation, and fatty acid metabolism mediate the presence of closely related species in distinct intertidal and cold-seep habitats

Bathyal cold seeps are isolated extreme deep-sea environments characterized by low species diversity while biomass can be high. The Hakon Mosby mud volcano (Barents Sea, 1,280 m) is a rather stable chemosynthetic driven habitat characterized by prominent surface bacterial mats with high sulfide concentrations and low oxygen levels. Here, the nematode Halomonhystera hermesithrives in high abundances (11,000 individuals 10 cm(-2)). Halomonhystera hermesi is a member of the intertidal Halomonhystera disjuncta species complex that includes five cryptic species (GD 1-5). GD1-5's common habitat is characterized by strong environmental fluctuations. Here, we compared the transcriptomes of H. hermesi and GD1, H. hermesi's closest relative. Genes encoding proteins involved in oxidative phosphorylation are more strongly expressed in H. hermesi than in GD1, and many genes were only observed in H. hermesi while being completely absent in GD1. Both observations could in part be attributed to high sulfide concentrations and low oxygen levels. Additionally, fatty acid elongation was also prominent in H. hermesi confirming the importance of highly unsaturated fatty acids in this species. Significant higher amounts of transcription factors and genes involved in signaling receptor activity were observed in GD1 (many of which were completely absent in H. hermesi), allowing fast signaling and transcriptional reprogramming which can mediate survival in dynamic intertidal environments. GC content was approximately 8% higher in H. hermesi coding unigenes resulting in differential codon usage between both species and a higher proportion of amino acids with GC-rich codons in H. hermesi. In general our results showed that most pathways were active in both environments and that only three genes are under natural selection. This indicates that also plasticity should be taken in consideration in the evolutionary history of Halomonhystera species. Such plasticity, as well as possible preadaptation to low oxygen and high sulfide levels might have played an important role in the establishment of a cold-seep Halomonhystera population

Differences in life-histories refute ecological equivalence of cryptic species and provide clues to the origin of bathyal Halomonhystera (Nematoda)

The discovery of morphologically very similar but genetically distinct species complicates a proper understanding of the link between biodiversity and ecosystem functioning. Cryptic species have been frequently observed to co-occur and are thus expected to be ecological equivalent. The marine nematode Halomonhystera disjuncta contains five cryptic species (GD1-5) that co-occur in the Westerschelde estuary. In this study, we investigated the effect of three abiotic factors (salinity, temperature and sulphide) on life-history traits of three cryptic H. disjuncta species (GD1-3). Our results show that temperature had the most profound influence on all life-cycle parameters compared to a smaller effect of salinity. Life-history traits of closely related cryptic species were differentially affected by temperature, salinity and presence of sulphides which shows that cryptic H. disjuncta species are not ecologically equivalent. Our results further revealed that GD1 had the highest tolerance to a combination of sulphides, high salinities and low temperatures. The close phylogenetic position of GD1 to Halomonhystera hermesi, the dominant species in sulphidic sediments of the Hakon Mosby mud volcano (Barent Sea, 1280 m depth), indicates that both species share a recent common ancestor. Differential life-history responses to environmental changes among cryptic species may have crucial consequences for our perception on ecosystem functioning and coexistence of cryptic species

Improving air filter efficiency as a strategy to reduce children’s exposure to traffic related air pollutants in energy-efficient classrooms

This study was organised to quantify the effect of upgrading the filter efficiency in balance ventilation systems on indoor exposure to traffic-related air pollution, in 4 primary school classrooms. The standard air filters (EU F7) were compared with more efficient EU F9, and with F7+active carbon filters. Particulate matter (PM), ultrafine particles (UFP), black carbon (BC), PM2.5, organic/elemental carbon in PM2.5 (EC/OC), and NO2 were quantified, air tightness and air supply rates were assessed and pupils’ indoor comfort was surveyed. Analysis of indoor air as function of outdoor air and filter type indicated a significant but small reduction of indoor levels when upgrading the filter, except for PM10, TSP and UFP. The indoor comfort survey indicated a small but significant and positive effect as well

Effect of Arbuscular Mycorrhizal Fungi on Pratylenchus penetrans Infestation in Apple Seedlings under Greenhouse Conditions

A major problem in fruit cultivation in Flanders is replant disease due to a lack of uncultivated soils available for new plantings. Replant disease can cause poor growth and affect time to full production, however Arbuscular Mycorrhizal Fungi (AMF) can prove their usefulness with regard to these problems. To further investigate the effect of AMF on nematodes, different AMF species were amended to potted apple seedlings in the presence of the nematode Pratylenchus penetrans. Generally, apple seedlings grew better in the presence of nematodes when mycorrhiza were inoculated into the soil. Moreover, a positive correlation (R2 ≥ 0.88) was found between the percentage root length colonization of the roots of apple seedlings, by AMF species, and nematode reduction in the soil of the seedlings. Indigenous AMF could colonize the roots of apple seedlings the most efficiently, resulting in a higher biocontrol effect. Besides, a synergistic effect was observed when two AMF strains were applied together leading to a significant growth response of the seedlings

Description of two free-living nematode species of Halomonhystera disjuncta complex (Nematoda: Monhysterida) from two peculiar habitats in the sea

Morphological descriptions of two Halomonhystera species (Nematoda, Monhysterida) are presented (Halomonhystera hermesi and Halomonhystera socialis). Halomonhystera hermesi sp. n. occurs in a dense monospecific and homogeneous population on bacterial mats in the HAyenkon Mosby mud volcano in the Barents Sea at a depth of 1,280 m. The species is an endemic lineage distinctly separated from other shallow-water cryptotaxa of the Halomonhystera disjucta species complex on the base of the mitochondrial gene cytochrome oxidase subunit I (genetic divergence 19.6-23.8 %) and nuclear genetic markers, and on the base of morphometrics by Van Campenhout et al. (2014). H. socialis (Butschli 1874) is redescribed on the basis of White Sea specimens. This species dwells in mass on the detached kelp accumulation in the upper sublittoral. H. socialis is differentiated from other species of the Halomonhystera disjuncta complex morphometrically by a larger body size and by genetic divergence in nuclear markers. The genus Halomonhystera Andrassy 2006 is redefined, and its morphospecies list is reviewed. Species H. bathislandica (Riemann 1995) comb. n., H. fisheri (Zekely et al. 2006) comb. n., H. islandica (De Coninck 1943) comb. n. and H. vandoverae (Zekely et al. 2006) comb. n. are transferred to Halomonhystera from Thalassomonhystera; H. paradisjuncta (de Coninck 1943) comb. n., H. rotundicapitata (Filipjev 1922) comb. n. and H. taurica (Tsalolikhin 2007) comb. n. transferred to Halomonhystera from Geomonhystera. Halomonhystera ambiguoides (Butschli 1874) is considered as species inquirenda because of incompleteness of its diagnosis

III-V silicon heterogeneous integration for integrated transmitters and receivers

Silicon is excellent material for realizing compact nanophotonic ICs operating at wavelengths in the telecom range. Moreover, the desired circuits can be realized with the most advanced equipment available, used also for the fabrication of high-end electronic circuits. Efficient light emission and amplification directly from silicon remains a bottleneck however. Therefore, we developed an alternative approach, based on the heterogeneous integration of III-V epitaxial material and silicon nanophotonic circuits. Following fabrication and planarization of the latter, small unprocessed dies of InP-based epitaxial material are bonded on top. Next, the substrate of these dies is removed down to an etch stop layer. Finally the desired active optoelectronic devices are processed in the remaining Ill-V layers using waferscale processes. The critical alignment between the sources and the underlying nanophotonic circuits is ensured through accurate lithography. In this paper we review some recent devices fabricated through this integration process